PLK1 degradation-inducing compounds with increased rigidity

Abstract

Novel dihydropteridone or pyrimidodiazepinone analogs based on PLK1 degrading molecules are disclosed. These PLK1 degrading molecules are proteolysis-targeting chimeras (PROTACs) that recruit PLK1 protein to CRBN E3 ubiquitin ligase through an optimized rigid linker. These compounds can induce PLK1 degradation with improved drug properties and can be utilized, for example, as payloads for antibody-drug conjugates (ADCs) for cancer therapy.

Description

[Technical Field]

[0001] The present disclosure relates to novel PLK1 degradation-inducing compounds, methods for producing the same, and uses thereof. [Background technology]

[0002] Polo-like kinase 1 (PLK1) is a serine / threonine kinase widely distributed in eukaryotic cells and plays important roles in various stages of the cell cycle. PLK1 has long been considered a potential drug target for cancer treatment, and various PLK1 inhibitors have been evaluated in clinical trials. Among them, BI-2536 is a first-in-class, highly selective, ATP-competitive small molecule based on dihydropteridone analogs that inhibits PLK1 enzymatic activity by blocking the ATP-binding site. BI-2536 has also been shown to be a potent inhibitor of BRD4, demonstrating the ability of a single compound to target multiple pharmacological targets. However, existing PLK1 inhibitors have largely failed or been discontinued in clinical trials due to their inability to sufficiently inhibit PLK1 activity at clinically safe concentrations. Clinical trials revealed that the pharmacological mechanism of small molecule inhibitors is to inhibit enzymatic activity by binding to the active site of PLK1, and that these inhibitors are not sufficiently effective in developing new drugs that aim to suppress PLK1 activity in cancer cells and elicit anti-cancer effects.

[0003] PROTACs (proteolysis targeting chimeras) are bispecific molecules consisting of a target protein binder and an E3 ubiquitin ligase binder linked by a linker. PROTACs can promote the proteasomal degradation of target proteins by recruiting ubiquitin ligase to the target protein. Because the removal of oncogenic proteins in cancer cells can achieve better therapeutic effects than simply inhibiting the protein, PROTACs have been developed as a new therapeutic modality in the field of anti-cancer therapy.

[0004] In relation to PLK1-degrading PROTACs, a PLK1 / BRD4 dual-targeting PROTAC is disclosed in CN109879877A. The inventors of this publication noted that both BRD4 and PLK1 are effective therapeutic targets for acute myeloid leukemia, and confirmed that the PROTAC induces the degradation of both proteins and inhibits the division of human acute leukemia cells (Mu, Xupeng, et al., "Protein targeting chimeric molecules specific for dual bromodomain 4 (BRD4) and Polo-like kinase 1 (PLK1) proteins in acute myeloid leukemia cells." Biochemical and biophysical research communications 521.4 (2020):833-839).

[0005] However, CN109879877A only discloses a limited form of PROTAC in which a dihydropteridone analog is linked to a thalidomide analog, a CRBN (cereblon) binder, via an alkyl or PEG linker. In recent years, the PROTAC field has undergone a major shift from alkyl and polyethylene glycol, which are easy to synthesize and handle, to linker forms that reduce the flexibility or degree of freedom of the ternary complex while maintaining the efficacy of the degradation-inducing molecule, optimizing rigidity and functionality (see Troup, Robert I., Charlene Fallan, and Matthias GJ Baud. "Current strategies for the design of PROTAC linkers: a critical review." Exploration of Targeted Anti-tumor Therapy 1.5 (2020):273).

[0006] It is now widely accepted that linker molecules play more than just a linking molecule connecting the protein of interest (POI) and the E3 warhead. In fact, linkers play a special role in exerting PROTAC degradation potency and efficiency by participating in the formation of a ternary complex of PROTACs. Furthermore, the physicochemical profile of a PROTAC (e.g., potency, solubility, or stability) varies depending on the linker used. Therefore, modification of the linker structure, such as replacing the alkyl / PEG linker at the initial stage, is essential for developing effective PROTAC compounds as therapeutic agents. However, the task of developing a PROTAC linker capable of forming a target-specific and stable ternary complex to induce sufficient target protein degradation is extremely challenging and requires extensive experimental trial and error in the field.

[0007] The present applicant has previously developed PLK1-targeted PROTACs with targeted degradation effects using different PLK1 binding moieties (International Patent Publications WO2021 / 194318 A1, WO2021 / 194319 A1, WO2021 / 194320 A1, and WO2021 / 194321 A1). However, predicting the anchor / linker / warhead combination that elicits optimal degradation due to the structural complexity and dynamics of the ternary complex poses a tremendous challenge. In light of this, the present inventors have succeeded in synthesizing novel, optimized PLK1 degraders that effectively degrade PLK1 by introducing rigid PROTAC linkers based on amine and ring structures, thereby improving the pharmacological profile required for PROTAC-based drugs. Summary of the Invention [Problem to be solved by the invention]

[0008] The main objective of the present invention is to provide alternative novel PLK1 degrading molecules with increased rigidity through linker optimization. [Means for solving the problem]

[0009] To achieve this, the present invention provides novel PROTAC compounds with a rigid linker inserted with two saturated six-membered rings selectively mediated by short chains of limited versatility.

[0010] Design of novel PLK1 degrading molecules In one general aspect, the present disclosure provides novel compounds represented by Formula I: [Chemical formula I] [ka]

[0011] In the above formula, L1 is a covalent bond or -(X5) 1~3 - {wherein each X5 is independently -CH2- or -NH-, provided that -NH- is absent or present at most one time in L1};

[0012] L2 is a covalent bond or -(X6) 1~3 - {wherein X6 is each independently -CH2-, -C(O)-, -NH-, or -CH(NH2)-, provided that -C(O)-, -NH-, -N(CH3)-, and -CH(NH2)- are each independently absent or present at most 1 time in L2};

[0013] L3 is [ka] or [ka] where L3 is [ka] covalently bonded to X4 via};

[0014] X1, X2, X3 and X4 are each independently CH or N; X7 and X 8a are each independently a covalent bond or -CH2-; X 8b is -H or -CH3; R1 is -OCH3 or -OCF3;

[0015] ULM is a moiety represented by the following chemical formula II-1, II-2, or II-3: [Chemical formula II-1] [ka] [Chemical formula II-2] [ka] [Chemical formula II-3] [ka] In the above formula, Ring U is phenyl or a 5- or 6-membered heteroaryl; U1 is -NH-, -NHCH2-, -NHCH2CH2-, -CH2NH-, -CH2CH2NH-, -NHCO-, -CONH- or -O-; U2 is CH2 or C(O); R U is a halo.

[0016] In Formula I, [ka] is composed of two types of saturated six-membered rings ( [ka] and [ka] ) is selectively mediated by short chains L1, L2, and L3, linking ULM and PTM in a para-orientation. The rigidity of the PROTAC linker may contribute to creating a more stable form for the interaction between CRBN E3 ligase and PLK1, allowing PLK1 to be placed within the ubiquitination zone.

[0017] In one embodiment, one to three of X1 to X4 are N. The present invention focuses on the fact that the piperidine or piperazine ring possesses a basic center through a protonatable amino group, and can serve as a center for a linker moiety to improve rigidity or solubility through the proton.

[0018] In Formula I, L1, L2, and L3 can impart overall favorable rigidity and solubility to the PROTAC linker within Formula I via the two types of six-membered rings described above.

[0019] In L1 of formula I, -(X5) 1~3 - indicates that -(X5)- units are linked in sequence 1 to 3 times, where each unit -(X5)- may be the same or different.

[0020] In one embodiment, L1 is a covalent bond, wherein ULM is covalently linked to X1.

[0021] In one embodiment, L1 is -(CH2) 1~3 -, for example, -CH2-, -CH2CH2- or -CH2CH2CH2, where -NH- is absent in L1.

[0022] In one embodiment, L1 is -NH-, -NHCH2-, -CH2NH-, -NHCH2CH2-, -CH2NHCH2-, or -CH2CH2NH-, wherein -NH- occurs once in L1.

[0023] In L2 of formula I, -(X6) 1~3 - indicates that -(X6)- units are linked in sequence 1 to 3 times, where each unit -(X6)- may be the same or different.

[0024] In one embodiment, L2 is a covalent bond, where two six-membered rings are covalently linked.

[0025] In one embodiment, L2 is -(CH2) 1~3 -, for example -CH2-, -CH2CH2- or -CH2CH2CH2-, where no functional group is present within L2.

[0026] In one embodiment, L2 is -(R x )-, -(R x )-CH2-, -CH2-(R x )-, -(R x )-(R x )-, -(R x )-CH2-CH2-, -CH2-(R x )-CH2-, -CH2-CH2-(R x )-, -(R x )-(R x )-CH2-, -(R x )-CH2-(R x )-, -CH2-(R x )-(R x )-or-(R x )-(R x )-(R x )-, where R x is -C(O)-, -NH-, -N(CH3)- or -CH(NH2); each unit -(R x )- are different. Thus, -C(O)-, -NH-, -N(CH3)- or -CH(NH2), if present, occurs once in L2.

[0027] In one embodiment, L3 is: [ka] where the amide group can mediate a network of interactions involving residues from both the N- and C-sites of PLK1, with its NH and CO forming hydrogen bonds with core amino acid residues of PLK1, e.g., the main-chain carbonyl of LEU59 residue in the glycine-rich loop and the side chain of ARG57, respectively.

[0028] In one embodiment, L3 is: [ka] where the oxadiazole group can further improve PROTAC properties, including metabolic stability.

[0029] The PROTAC linker design disclosed in Formula I has been optimized for the anchor / linker / warhead, which can induce physicochemical properties that effectively improve efficacy.

[0030] ULM, represented by formula II-1 or II-2, is a CRBN ligand in which a glutarimide is conjugated to a phenyl or heteroaryl ring directly or via a short-chain moiety.

[0031] In Formula II-1, Ring U can be phenyl or a 5- or 6-membered heteroaryl, including pyrrolyl, furanyl, thienyl, oxazolyl, isoxazolyl, thiazolyl, imidazolyl, triazolyl, tetrazolyl, pyridinyl, pyrimidinyl, pyrazinyl, pyridazinyl, or pyrazolyl. In one embodiment, Ring U is phenyl or pyridinyl.

[0032] In one embodiment, Formula II-1 is selected from the following: [ka]

[0033] In Formula II-1, L1 and the glutarimide moiety in Formula II-1 can be linked to each other in the ortho-, meta-, or para-orientation to ring U. In one embodiment, they are linked in the para-orientation.

[0034] In one embodiment, Formula II-1 is selected from the following: [ka]

[0035] In Formula II-2, U1 can be -NH-, -NHCH2-, -NHCH2CH2-, -CH2NH-, -CH2CH2NH-, -NHCO-, -CONH-, or -O-. In one embodiment, U1 is -NH-.

[0036] In one embodiment, Formula II-2 is as follows: [ka]

[0037] In formulas II-1, II-2 and II-3, R U is fluoro, chloro, bromo, or iodo. U is fluoro.

[0038] In one embodiment of the present disclosure, Formula I is Formula I-1: [Chemical formula I-1] [ka]

[0039] In the above formula, L 1a is -CH2-, -NH-, -CH2CH2-, -NHCH2-, -CH2NH-, -CH2CH2CH2-, -NHCH2CH2-, -CH2NHCH2- or -CH2CH2NH-.

[0040] In one embodiment of the present disclosure, Formula I is Formula I-2: [Chemical formula I-2] [ka]

[0041] In the above formula, X9 is —CH2— or —CH(NH2)—.

[0042] In one embodiment of the present disclosure, Formula I is Formula I-3: [Chemical formula I-3] [ka]

[0043] In the above formula, X 10 is a covalent bond, -NH- or -CH(NH2)-; X 11 is a covalent bond or -CH2-.

[0044] In one embodiment of the present disclosure, Formula I is Formula I-4: [Chemical formula I-4] [ka]

[0045] In the above formula, L 1b is a covalent bond or -CH2NH-; L 2b is a covalent bond, -CH2NH-, -CH2N(CH3)-, or -CH2CH(NH2)C(O)-; X 8a is a covalent bond or -CH2-; X 8b is -H or -CH3.

[0046] In one embodiment of the present disclosure, the compound of Formula I is selected from the group consisting of compounds 1-25. [Table 1]

[0047] [Table 1-1]

[0048] [Table 1-2]

[0049] [Table 1-3]

[0050] [Table 1-4]

[0051] [Table 1-5]

[0052] In yet another aspect, there is provided a compound represented by Formula III: [Chemical formula III] [ka]

[0053] In the above formula, L2 is -CH2-, -NHCH2-, -CH2NH-, -CH(NH2)CH2-, -CH2CH(NH2)-, or -CH2CH2C(O)-; X1, X2, X3 and X4 are each independently CH or N; X7 is a covalent bond or -CH2-; R 2a and R 2b is -halo; or R 2a and R 2bare linked to each other to form a 3- to 6-membered ring, for example, a cyclopropane ring; R3 is -C 1-3 alkyl or 3-7 membered cycloalkyl, for example, isopropyl or cyclopentyl;

[0054] ULM is a moiety represented by formula II-4: [Chemical formula II-4] [ka] In the formula, U3 is a covalent bond or -NH-; R U is a halo.

[0055] In one embodiment of the present disclosure, the compound represented by formula III is selected from the group consisting of compounds 26-31. [Table 2]

[0056] [Table 2-1]

[0057] [Table 2-2]

[0058] PROTAC linkers can contain a variety of functional groups, including amines, amides, ethers, alkylamines, single and multiple C-C bonds, etc. As an alternative group, cyclic scaffolds containing piperidine or piperazine can impart a certain degree of rigidity to the linker, which can be further tuned with additional groups (see Desantis, Jenny, et al., "PROTACs bearing piperazine-containing linkers: what effect on their protonation state?" RSC Advances 12.34 (2022):21968-21977).

[0059] Although the fundamental properties of these functional groups can serve as a starting point for optimizing PROTAC design, achieving successful PROTAC linker design remains extremely challenging because it is unpredictable to determine which anchor, linker, and warhead combination will induce a basic level of target protein degradation (see Troup, Robert I., Charlene Fallan, and Matthias GJ Baud. "Current strategies for the design of PROTAC linkers: a critical review." Exploration of Targeted Anti-tumor Therapy 1.5 (2020):273.).

[0060] Against this background, the present inventors have demonstrated that newly designed PROTACs with rigid linkers within the full range of formula I or III exhibit sufficient levels of PLK1 degradation efficacy, a surprising result that would not have been predicted from earlier-stage PROTACs with flexible PEG or alkyl linkers.

[0061] In one embodiment, the compounds of the present disclosure may be in the form of a salt, preferably a pharmaceutically acceptable salt, which, in the present disclosure, refers to any organic or inorganic acid addition salt that is relatively non-toxic and can be used at harmless concentrations to effectively affect patients, and the side effects induced by the salt do not impair the beneficial effects of the novel compounds of the present disclosure.

[0062] In one embodiment, the compounds of the present disclosure may exist in the form of racemates, enantiomers, rotamers, tautomers, N-oxides, or any stereoisomeric form, as specifically indicated, unless the context specifically excludes otherwise.

[0063] In one embodiment, the compounds of the present disclosure may exist in the form of hydrates or solvates.

[0064] In one embodiment, the compounds of the present disclosure can exist in the form of chimeric molecules conjugated to functional macromolecules through chemical linkers. In certain embodiments, the macromolecules are biomolecules, including nucleic acids, aptamers, carbohydrates, peptides or fragments thereof, and antibodies or fragments thereof.

[0065] Synthesis of novel PLK1 degrading molecules In one embodiment, the novel compounds of the present disclosure can be prepared by synthetic methods known in the art of organic chemistry or by modification techniques obvious to those of ordinary skill in the art, for example, according to the following Reaction Schemes 1 to 3.

[0066] [Reaction Scheme 1] [ka]

[0067] [Reaction Scheme 2] [ka]

[0068] [Reaction Scheme 3] [ka]

[0069] In the above reaction scheme, the PTM is [ka] or [ka] And Linker is, [ka] and ULM is as defined above. RG 1 , R.G. 2 , R.G. 2a , R.G. 2b , R.G. 3 , R.G. 3a , R.G. 3b and R.G. 4 is a moiety containing a suitable reactive group in the field of organic synthesis that can link PROTAC intermediates through covalent bond formation. Depending on the specific reactive group, the formation of the covalent bond can be achieved by synthetic reactions such as, but not limited to, amide formation, ester formation, carbamate formation, urea formation, ether formation, amine formation, and various carbon-carbon single and double bond formations, click chemistry, etc.

[0070] Each step in the above schemes may involve single or multiple synthetic steps. Isolation and purification of the products may be achieved by standard procedures known to one of ordinary skill in the art of organic chemistry.

[0071] Uses of novel PLK1 degradation molecules In one embodiment, the novel compounds of the present disclosure are PLK1 degrading molecules that induce PLK1 proteolysis in cells.

[0072] In humans, PLK-1 is an enzyme encoded by the polo-like kinase 1 (PLK1) gene, and the protein sequence is known in the art (see, for example, NCBI Reference Sequence NP_005021.) The PLK1 protein structure contains an N-terminal serine / threonine kinase domain and C-terminal repeats of polo-box domains (PBDs), the phosphorylation of which is directly related to the enzymatic activity of PLK1.

[0073] The PROTACs of the present invention can induce proteasomal degradation of intracellular PLK1 by recruiting CRBN ubiquitin ligase to PLK1, as demonstrated by the experimental examples in the present disclosure. For example, the present disclosure revealed that compounds 1 to 31 have PLK1 degradation activity as demonstrated by luciferase assay in a HeLa LgBit cell system, and induce inhibitory activity against cancer cell viability as demonstrated by cell viability assays in small cell lung cancer (SCLC) cell lines H69 and H526.

[0074] In one embodiment, the PROTACs of the present invention eliminate rather than inhibit target proteins, and therefore have superior therapeutic efficacy compared to the small molecule PLK1 inhibitors from which they are derived. As a result, the PROTACs of the present invention can be used to treat PLK1-related disorders or conditions in which abnormal expression of PLK1 protein contributes to the onset and / or progression of the disease.

[0075] In the present disclosure, a PLK1-related disorder or disease refers to any disorder or condition that can be treated, delayed, inhibited, or prevented by inducing the degradation or inhibiting the activity of PLK1, including, but not limited to, cancer, benign tumors, or neurological diseases.

[0076] In one embodiment, the PROTAC of the present invention can have anticancer activity against cancer cells expressing PLK1 by ablation of PLK1, a core oncogenic regulator of the cell cycle. The cancers include all carcinomas for which inhibition of PLK1 activity can show preventive or therapeutic efficacy, and may be solid cancers or hematological cancers. For example, the cancers include squamous cell carcinoma, small cell lung cancer, non-small cell lung cancer, lung adenocarcinoma, lung squamous cell carcinoma, peritoneal cancer, skin cancer, cutaneous or intraocular melanoma, rectal cancer, anal muscle cancer, esophageal cancer, small intestine cancer, endocrine cancer, parathyroid cancer, adrenal cancer, soft tissue sarcoma, urethral cancer, chronic or acute leukemia, lymphocytic lymphoma, hepatocellular carcinoma, gastrointestinal tract cancer, gastric cancer, pancreatic cancer, glioblastoma, neuroblastoma, glioma, and cervical cancer. The cancer may be one or more selected from the group consisting of, but not limited to, ovarian cancer, liver cancer, bladder cancer, liver tumor, breast cancer, colon cancer, colorectal cancer, endometrial or uterine cancer, salivary gland cancer, kidney cancer, prostate cancer, vulvar cancer, thyroid cancer, head and neck cancer, brain cancer, osteosarcoma, bone cancer, large cell lymphoma, adrenocortical tumor, T-cell lymphoma / leukemia, neuroendocrine cancer, neuroendocrine tumor, bile duct cancer, etc. The cancer includes not only primary cancer but also metastatic cancer.

[0077] The benign tumor includes all benign tumors that can show preventive or therapeutic efficacy by inhibiting PLK1 activity, such as precancerous benign tumors, and may be a solid tumor or a hematological tumor. For example, the tumor may be one or more selected from the group consisting of Barrett's esophagus, colorectal adenoma and polyp, breast fibroadenoma and cyst, monoclonal gammopathy of undetermined significance (MGUS), and monoclonal lymphocytosis, but is not limited thereto.

[0078] The neurological disease includes all neurological diseases for which the inhibition of PLK1 activity can show preventive or therapeutic efficacy, and specifically may be one or more selected from the group consisting of central nervous system diseases, neurodegenerative diseases, Alzheimer's disease, Parkinson's disease, multiple sclerosis, Huntington's disease, senile dementia, epilepsy, amyotrophic lateral sclerosis, stroke, nerve damage after brain or spinal cord injury, and axonal degeneration-related diseases, but is not limited thereto.

[0079] To improve drug activity, any strategy known in the PROTAC field can be applied to the PROTACs of the present invention, including photochemically tunable PROTACs (PHOTACs), hypoxia-activated PROTACs, folate-caged PROTACs, antibody-PROTAC conjugates (Ab-PROTACs), aptamer-PROTAC conjugates (APCs), and BCL-XL PROTACs (see Zhao, Chunlong, and Frank J. Dekker, "Novel Design Strategies to Enhance the Efficiency of Proteolysis Targeting Chimeras," ACS Pharmacology & Translational Science 5.9 (2022):710-723).

[0080] In one embodiment, the PROTACs of the present invention can be utilized as the payload of an antibody-drug conjugate (ADC), such as an antibody-PROTAC conjugate (Ab-PROTAC). ADCs enable the delivery of a cytotoxic payload specifically to cancer cells, thereby achieving maximum efficacy in cancer cells while minimizing undesirable effects in non-cancerous cells. Therefore, Ab-PROTACs utilizing the PROTACs of the present invention may be a strategy for improving the tissue and cell-type selectivity of PROTACs.

[0081] In one embodiment, the present disclosure provides a pharmaceutical composition comprising a PROTAC of the present invention, wherein the PROTAC compound is conjugated to an antibody or antigen-binding fragment thereof via a linker.

[0082] In one embodiment, the present disclosure provides an antibody-drug conjugate comprising an antibody or antigen-binding fragment thereof and a PROTAC of the invention, wherein the PROTAC compound is conjugated to the antibody or antigen-binding fragment thereof via a linker.

[0083] In certain embodiments, a linker chemically links an antibody or antigen-binding fragment thereof to a PROTAC of the invention, wherein a functional group within the PROTAC compound is modified to form a covalent bond with the linker moiety, hi certain embodiments, the functional group is an amine group within the PROTAC linker or E3L binder moiety of the compound.

[0084] In certain embodiments, the antibody or antigen-binding fragment thereof is cancer cell-specific and comprises one or more compound molecules of Formula I or III. In certain embodiments, the linker is a cleavable or non-cleavable linker.

[0085] The present disclosure also provides a pharmaceutical composition comprising a PROTAC compound of the present invention and at least one pharmaceutically acceptable carrier. In one embodiment, the pharmaceutical composition comprises an effective amount of at least one PROTAC compound of the present invention and, optionally, one or more other active ingredients for combination therapy. In one embodiment, the pharmaceutical composition comprises one or more pharmaceutically acceptable additives or excipients.

[0086] In yet another embodiment of the present disclosure, there is provided a method for degrading PLK1 by treating an in vitro sample with a PROTAC of the present invention, wherein the sample may be, but is not limited to, mammalian cells, including human cells, cell culture medium, body fluids, or tissues. [Effects of the Invention]

[0087] The novel compounds of the present disclosure can induce PLK1 degradation in cells with improved PROTAC properties, such as, for example, potency, target selectivity, solubility, lipid affinity, permeability, stability, and toxicity, and thus can be effectively utilized in the treatment of PLK1-related disorders or conditions. DETAILED DESCRIPTION OF THE INVENTION

[0088] Unless otherwise defined, all technical or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. The terms used in describing the invention are intended solely to describe particular embodiments and are not intended to limit the present disclosure.

[0089] This disclosure provides synthetic methods and biological activity results for compounds 1-31.

[0090] The compounds of the present invention were purified and their structures were analyzed by the following methods.

[0091] device LCMS: Shimadzu LCMS-2020 HPLC: Agilent 1260 II LC, Agilent 1200 / G6410B NMR:BRUKER AVANCE / 400 MHZ SFC: SHIMADZU LC-30ADsf

[0092] LCMS analysis LCMS data were recorded on a Shimadzu LCMS-2020 equipped with an ESI (Electron Spray Ionization) system. The mobile phases used were 0.0375% TFA in water (solvent A) and 0.01875% TFA in ACN (solvent B). The columns used were Kinetex EVO C18 (2.1 × 30 mm, 5 μm) or HALO C18 (3.0 × 30 mm, 5 μm).

[0093] HPLC analysis For HPLC analysis, an Agilent 1260 II LC or an Agilent 1200 / G6410B was used. The mobile phase consisted of 0.0375% TFA in water (solvent A) and 0.01875% TFA in ACN (solvent B). The column used was a Zobrax Eclipse Plus C18 (4.6 × 150 mm, 3.5 μm) or a YMC ODS A (4.6 × 150 mm, 3 μm).

[0094] NMR analysis 1 H NMR spectra were recorded on a Bruker AVANCE III 400 MHz / 5 mm Probe (BBO).

[0095] SFC analysis For SFC analysis, a Shimadzu LC-30ADsf was used. CO2 (solvent A) and 0.05% DEA in IPA + ACN (solvent B) were used as the mobile phase. The column used was a Chiralpak AD-3 (50 × 4.6 mm, 3 μm). [Example]

[0096] Example 1. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(2-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)ethyl)piperazin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 1)

[0097] [ka]

[0098] Step 1. Synthesis of 4-(2,6-bis(benzyloxy)pyridin-3-yl)aniline (2) To a solution of 2,6-dibenzyloxy-3-bromo-pyridine (6 g, 16.21 mmol), 4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)aniline (4.62 g, 21.07 mmol) in dioxane (90 mL) and HO (9 mL) was added KCO (6.72 g, 48.62 mmol), Pd(dppf)Cl (1.19 g, 1.62 mmol) at 20 °C under N, and the temperature was raised to 110 °C and stirred for 6 h. LCMS confirmed the consumption of the starting material, and a peak of the desired mass (57%) was detected. The mixture was concentrated in vacuo. The residue was purified by silica gel chromatography (80 g SepaFlash® silica flash column, eluent: 0-20% EtOAc / petroleum ether gradient @ 200 mL / min) to afford the title compound (6.3 g, 16.14 mmol, 99.61% yield, 98% purity) as a yellow oil. MS (M+H) + =383.2

[0099] Step 2. Synthesis of 3-(4-aminophenyl)piperidine-2,6-dione (3) To a solution of 4-(2,6-bis(benzyloxy)pyridin-3-yl)aniline (6 g, 15.69 mmol) in DCM (50 mL) and MeOH (50 mL) was added Pd / C (1 g, 10% purity) under N2. The suspension was degassed and purged with hydrogen three times. The mixture was stirred under H2 (15 Psi) at 20 °C for 12 h. LCMS showed the remaining starting material (44%) and the desired mass peak (37%), and the mixture was stirred for an additional 12 h at 20 °C. LCMS confirmed the consumption of the starting material and the desired mass peak. The mixture was diluted with MeOH (100 mL) and filtered. The residue was concentrated under reduced pressure to give the title compound (2.4 g, 11.75 mmol, 74.91% yield) as a green solid. MS (M+H) + =205.1

[0100] Step 3. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(2-((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)ethyl)piperazin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 1)

[0101] To a solution of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-((1r,4R)-4-(4-(2-oxoethyl)piperazin-1-yl)cyclohexyl)benzamide (208.00 mg, 328.70 μmol) in DCM (10 mL) was added TEA (99.78 mg, 986.10 μmol, 137.25 μL) and 3-(4-aminophenyl)piperidine-2,6-dione (80.55 mg, 394.44 μmol) at 20° C. After stirring for 10 min at 20° C., NaBH(OAc) (209.00 mg, 986.10 μmol) was slowly added to the mixture and stirred for 2 h. LCMS confirmed the consumption of the starting material, and a peak of the desired mass (30%) was detected. The mixture was diluted with water (20 mL) and extracted with DCM (12 mL x 3). The organic phase was washed with NaHCO (12 mL x 3), dried over NaSO, filtered, and concentrated. The residue was purified by prep-TLC (SiO, DCM:MeOH = 10:1) to give 86 mg of product (95% purity by LCMS, HPLC). The product was dissolved in a mixture (20 mL, ACN:H2O = 1:3) and lyophilized to give the title compound (53 mg, 59.39 μmol, 18.07% yield, 92% purity) as a yellow solid. MS (M+H) + =821.2

[0102] [ka]

[0103] Example 2 Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 2)

[0104] [ka]

[0105] Step 1. Synthesis of tert-butyl 4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidine-1-carboxylate (3) A solution of 3-(4-aminophenyl)piperidine-2,6-dione (700 mg, 3.43 mmol), tert-butyl 4-formylpiperidine-1-carboxylate (657.91 mg, 3.08 mmol), and AcOH (20.58 mg, 342.76 μmol, 19.62 μL) in DCM (20 mL) was stirred at 15 °C for 0.5 h. NaBH(OAc) (3.3 g, 15.57 mmol) was added, and the resulting mixture was stirred at 15 °C for 12 h. LCMS showed the desired mass peak (84%). The mixture was diluted with water (20 mL) and adjusted to pH > 7 with saturated NaHCO solution. The mixture was extracted with DCM (50 mL × 2). The combined organic phase was dried over MgSO, filtered, and concentrated. The residue was purified by flash silica gel chromatography (20 g SepaFlash® silica flash column, eluent: 20-45% EtOAc / petroleum ether gradient @ 200 mL / min). The eluent was concentrated, and the residue was diluted with EtOAc (30 mL) and adjusted to pH < 7 with 1 M HCl solution. The aqueous phase was washed with EtOAc (30 mL x 2), and the EtOAc layer was removed. The aqueous phase was adjusted to pH > 7 with Na2CO3 solution and extracted with EtOAc (50 mL x 3). The combined organic layers were dried over Na2SO4, filtered, and concentrated under reduced pressure to give the title compound (360 mg, 896.64 μmol, 26.16% yield) as a pale blue solid. MS (M+Na) + =424.1.

[0106] Step 2. Synthesis of 3-(4-((piperidin-4-ylmethyl)amino)phenyl)piperidine-2,6-dione (4) To a solution of tert-butyl 4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidine-1-carboxylate (360 mg, 896.64 μmol) in DCM (10 mL) was added HCl / dioxane (4 M, 15 mL), and the mixture was stirred at 15° C. for 1 h. LCMS confirmed complete consumption of the starting material. The mixture was concentrated under reduced pressure to give the title compound (340 mg, HCl salt) as a white solid, which was used in the next step. MS (M+H) + =302.4.

[0107] Step 3. Synthesis of tert-butyl ((1r,4r)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (trans) (6) A mixture of 3-(4-((piperidin-4-ylmethyl)amino)phenyl)piperidine-2,6-dione (380 mg, 1.12 mmol, HCl salt), tert-butyl ((1s,4s)-4-iodocyclohexyl)carbamate (cis) (475.49 mg, 1.46 mmol), NaCO (357.64 mg, 3.37 mmol), and DIPEA (436.11 mg, 3.37 mmol, 587.75 μL) in ACN (10 mL) was stirred at 80 °C for 12 h. LCMS showed 23% of 3-(4-((piperidin-4-ylmethyl)amino)phenyl)piperidine-2,6-dione remaining, with a peak of the desired mass (6%) detected. To the mixture was added Na2CO3 (357.64 mg, 3.37 mmol), DIPEA (436.11 mg, 3.37 mmol, 587.75 μL) and tert-butyl ((1s,4s)-4-iodocyclohexyl)carbamate (cis) (182.88 mg, 562.39 μmol) and stirred at 80 °C for 2 h. Further tert-butyl ((1s,4s)-4-iodocyclohexyl)carbamate (cis) (182.88 mg, 562.39 μmol) was added and the resulting mixture was further stirred at 80 °C for 14 h, giving 11% 3-(4 It was confirmed that -((piperidin-4-ylmethyl)amino)phenyl)piperidine-2,6-dione remained, and a peak of the desired mass (60%) was detected. To the mixture was added tert-butyl ((1s,4s)-4-iodocyclohexyl)carbamate (cis) (91.44 mg, 281.20 μmol), and the reaction mixture was stirred at 80°C for 2 hours. Then, tert-butyl ((1s,4s)-4-iodocyclohexyl)carbamate (cis) (91.44 mg, 281.20 μmol) was added, and the resulting mixture was stirred at 80°C for 2 hours. LCMS confirmed that 3-(4-((piperidin-4-ylmethyl)amino)phenyl)piperidine-2,6-dione remained, and a peak of the desired mass (61%) was detected, and to the mixture was added tert-butyl ((1s,4s)-4-iodocyclohexyl)carbamate (cis) (365.76 mg, 1.12 mmol).The reaction mixture was stirred at 80 °C for 12 hours, and LCMS confirmed the presence of residual 3-(4-((piperidin-4-ylmethyl)amino)phenyl)piperidine-2,6-dione, with the desired mass peak (~50%) detected. The mixture was filtered, and the filter cake was washed with ACN (40 mL). The pH was adjusted to <7 with AcOH, and the resulting mixture was concentrated under reduced pressure. The residue was diluted with DCM (40 mL) and washed with water (30 mL x 2). The organic phase was dried over MgSO, filtered, and concentrated under reduced pressure. The residue was purified by prep-TLC (SiO, DCM:MeOH = 7:1) to give the title compound (63 mg, 126.34 μmol, 11.23% yield) as a brown solid. MS (M+H). + =499.3.

[0108] Step 4. Synthesis of 3-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)phenyl)piperidine-2,6-dione (trans) (7) A mixture of tert-butyl ((1r,4r)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (trans) (55 mg, 110.30 μmol) and HCl / dioxane (4 M, 3 mL) in DCM (3 mL) was stirred at 15° C. for 1 h. LCMS confirmed complete consumption of the starting material, and a peak of the desired mass was detected. The mixture was concentrated under reduced pressure to afford the title compound (50 mg, HCl salt) as a brown solid, which was used in the next step. MS (M+H) + =399.3.

[0109] Step 5. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (trans) (Compound 2) To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (35 mg, 82.26 μmol) in DMF (2 mL) was added HATU (46.92 mg, 123.39 μmol) and DIPEA (63.79 mg, 493.56 μmol, 85.97 μL) and the mixture was stirred at 15° C. for 15 min, after which 3-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)phenyl)piperidine-2,6-dione (trans) (50 mg, 114.94 μmol, HCl salt) was added and the reaction mixture was stirred at 15° C. for 1 h. LCMS showed complete consumption of 3-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)phenyl)piperidine-2,6-dione (trans) and the desired mass peak (65%). The mixture was diluted with HO (40 mL) and extracted with EtOAc (30 mL x 3). The combined organic layers were washed with brine (80 mL x 5), dried over NaSO, filtered, and concentrated under reduced pressure. The residue was purified by prep-TLC (SiO, DCM:MeOH = 7:1), and the eluate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150*25mm*10um; mobile phase: [water (TFA)-ACN]; B%: 31%-51%, 7 min). The eluate containing the residual DMF was concentrated under reduced pressure to remove most of the ACN. The residue was adjusted to pH >7 with NaHCO3 solution (0.5 mL) and extracted with DCM (10 mL x 3). The combined organic phase was washed with brine (10 mL x 4), dried over MgSO4, filtered, and concentrated. The residue was diluted with HO (10 mL) and ACN (5 mL) and lyophilized to give the title compound (15.2 mg, 18.10 μmol, 22.01% yield, 96% purity) as a white solid. MS (M+H) + =806.4.

[0110] [ka]

[0111] Example 3 Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(3-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)propyl)piperazin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 3)

[0112] [ka]

[0113] Step 1. Synthesis of tert-butyl ((1r,4r)-4-(4-benzylpiperazin-1-yl)cyclohexyl)carbamate (trans) (2A) To a solution of tert-butyl ((1r,4r)-4-aminocyclohexyl)carbamate (trans) (2 g, 9.33 mmol) and N-benzyl-2-chloro-N-(2-chloroethyl)ethan-1-amine (2.27 g, 8.46 mmol, HCl) in EtOH (20 mL) was added NaHCO (3.92 g, 46.66 mmol, 1.81 mL). The mixture was stirred at 85 °C for 16 h. LCMS confirmed complete consumption of tert-butyl ((1r,4r)-4-aminocyclohexyl)carbamate (trans), and a peak with the desired mass was detected. The reaction mixture was quenched with water (30 mL) at 25 °C and then extracted with EtOAc (160 mL). The organic layer was dried over NaSO, filtered, and concentrated under reduced pressure. The residue was triturated with EtOAc at 25° C. for 30 min to give the title compound (2.1 g, 5.34 mmol, 57.23% yield, 95% purity) as a white solid. MS (M+H) + =374.4.

[0114] Step 2. Synthesis of tert-butyl ((1r,4r)-4-(piperazin-1-yl)cyclohexyl)carbamate (trans) (3A) To a solution of tert-butyl ((1r,4r)-4-(4-benzylpiperazin-1-yl)cyclohexyl)carbamate (trans) (2.1 g, 5.62 mmol) in EtOH (20 mL) was added Pd / C (500 mg, 10% purity) and Pd(OH) / C (500 mg, 20% purity) under N. The suspension was degassed and purged with hydrogen three times. The mixture was stirred at 25 °C under H (30-40 Psi) for 16 h. TLC (DCM:MeOH = 10:1) confirmed complete consumption of tert-butyl ((1r,4r)-4-(4-benzylpiperazin-1-yl)cyclohexyl)carbamate (trans) and the formation of a new spot. The mixture was filtered, and the filtrate was concentrated under reduced pressure to give the title compound (1.52 g, 5.36 mmol, 95.40% yield) as a white solid.

[0115] Step 3. Synthesis of 3-(4-aminophenyl)propan-1-ol (2) To a solution of 3-(4-aminophenyl)propanoic acid (2 g, 12.11 mmol) in THF (30 mL) was added BH3-Me2S (10 M, 4.84 mL) at 0 °C. The mixture was stirred at 25 °C for 2 h. LCMS confirmed that 3-(4-aminophenyl)propanoic acid was consumed, and a peak of the desired mass was detected. To the mixture at 0 °C was added 40 mL of HCl (1 N). The mixture was adjusted to pH 7.4 with saturated NaHCO3 solution and extracted with EtOAc (120 mL). The organic layer was dried over Na2SO4, filtered, and concentrated under reduced pressure to give the title compound (1.82 g, 12.04 mmol, 99.42% yield) as a brown oil. The product was used in the next step without further purification. MS (M+H) + =152.0.

[0116] Step 4. Synthesis of 4-(3-((tert-butyldimethylsilyl)oxy)propyl)aniline (3) To a solution of 3-(4-aminophenyl)propan-1-ol (1.82 g, 12.04 mmol) in DCM (20 mL) was added TBSCl (2.18 g, 14.44 mmol, 1.78 mL) and Imid (1.64 g, 24.07 mmol). The mixture was stirred at 25 °C for 16 h. LCMS confirmed that 3-(4-aminophenyl)propan-1-ol was consumed, and a peak with the desired mass was detected. To the mixture at 0 °C was added 50 mL of HCl (1 N) solution, followed by extraction with EtOAc (100 mL). The combined organic layers were dried over Na SO , filtered, and concentrated under reduced pressure to give a residue. The residue was purified by flash silica gel chromatography (ISCO®; 40 g SepaFlash® silica flash column, eluent: 0-20% EtOAc / petroleum ether gradient @ 50 mL / min) to afford the title compound (2.9 g, 10.92 mmol, 90.76% yield) as a brown oil. MS (M+H) + =266.1.

[0117] Step 5. Synthesis of 3-((4-(3-((tert-butyldimethylsilyl)oxy)propyl)phenyl)amino)piperidine-2,6-dione (5) To a solution of 4-(3-((tert-butyldimethylsilyl)oxy)propyl)aniline (2.7 g, 10.17 mmol) and 3-bromopiperidine-2,6-dione (4.88 g, 25.43 mmol) in ACN (15 mL) was added NaHCO (4.96 g, 58.99 mmol, 2.30 mL). The mixture was stirred at 80 °C for 14 h. LCMS confirmed complete consumption of 4-(3-((tert-butyldimethylsilyl)oxy)propyl)aniline, and a peak with the desired mass was detected. The mixture was filtered and concentrated under reduced pressure to give a residue. The residue was purified by flash silica gel chromatography (ISCO®; 20 g SepaFlash® silica flash column, eluent: 0-17% EtOAc / petroleum ether gradient @ 120 mL / min) to afford the title compound (0.78 g, 2.07 mmol, 20.37% yield) as a blue solid. MS (M+H) + =377.4.

[0118] Step 6. Synthesis of 3-((4-(3-hydroxypropyl)phenyl)amino)piperidine-2,6-dione (6) To a solution of 3-((4-(3-((tert-butyldimethylsilyl)oxy)propyl)phenyl)amino)piperidine-2,6-dione (0.78 g, 2.07 mmol) in dioxane (8 mL) was added HCl / dioxane (4 M, 16 mL). The mixture was stirred at 25° C. for 1 h. LCMS confirmed complete consumption of 3-((4-(3-((tert-butyldimethylsilyl)oxy)propyl)phenyl)amino)piperidine-2,6-dione, and a peak of the desired mass was detected. The mixture was concentrated to give the title compound (0.54 g, 2.06 mmol, 99.39% yield) as a blue solid. The product was used in the next step without further purification. MS (M+H) + =263.3.

[0119] Step 7. Synthesis of 3-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)propyl 4-methylbenzenesulfonate (7) To a solution of 3-((4-(3-hydroxypropyl)phenyl)amino)piperidine-2,6-dione (0.54 g, 2.06 mmol) in DCM (6 mL) was added TEA (624.95 mg, 6.18 mmol, 859.63 μL) and TosCl (588.72 mg, 3.09 mmol). The mixture was stirred at 20° C. for 12 h. LCMS confirmed complete consumption of 3-((4-(3-hydroxypropyl)phenyl)amino)piperidine-2,6-dione, and a peak with the desired mass was detected. The mixture was concentrated to obtain the residue. The residue was purified by flash silica gel chromatography (ISCO®; 40 g SepaFlash® silica flash column, eluent: 0-50% EtOAc / petroleum ether gradient @ 80 mL / min) to afford the title compound (710 mg, 1.62 mmol, 78.67% yield, 95% purity) as a blue solid. MS (M+H) + =417.1.

[0120] Step 8. Synthesis of tert-butyl ((1r,4r)-4-(4-(3-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)propyl)piperazin-1-yl)cyclohexyl)carbamate (trans) (8) To a solution of 3-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)propyl 4-methylbenzenesulfonate (0.4 g, 960.41 μmol) and tert-butyl ((1r,4r)-4-(piperazin-1-yl)cyclohexyl)carbamate (trans) (0.45 g, 1.59 mmol) in DMF (4 mL) was added DIPEA (744.76 mg, 5.76 mmol, 1.00 mL) and NaI (28.79 mg, 192.08 μmol). The mixture was stirred at 25° C. for 16 h. LCMS confirmed complete consumption of 3-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)propyl 4-methylbenzenesulfonate, and a peak with the desired mass was detected. The reaction mixture was quenched with HO (20 mL) at 25 °C and extracted with EtOAc (120 mL). The combined organic phases were washed with brine (20 mL), dried over NaSO, filtered, and concentrated under reduced pressure to give a residue. The residue was purified by flash silica gel chromatography (ISCO®; 20 g SepaFlash® silica flash column, eluent 0–20% MeOH / EtOAc @ 50 mL / min) to give the title compound (0.227 g, 430.17 μmol, 44.79% yield) as a yellow solid. MS (M+H) + =528.3.

[0121] Step 9. Synthesis of 3-((4-(3-(4-((1r,4r)-4-aminocyclohexyl)piperazin-1-yl)propyl)phenyl)amino)piperidine-2,6-dione (trans) (9) To a solution of tert-butyl ((1r,4r)-4-(4-(3-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)propyl)piperazin-1-yl)cyclohexyl)carbamate (trans) (0.1 g, 189.50 μmol) in DCM (0.3 mL) was added TFA (153.50 mg, 1.35 mmol, 0.1 mL). The mixture was stirred at 25° C. for 1 h. LCMS confirmed complete consumption of tert-butyl ((1r,4r)-4-(4-(3-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)propyl)piperazin-1-yl)cyclohexyl)carbamate (trans), and a peak with the desired mass was detected. The mixture was concentrated to give the title compound (0.1 g, 184.64 μmol, 97.43% yield, TFA) as a yellow oil. The product was used in the next step without further purification. MS (M+H) + =428.5.

[0122] Step 10. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(3-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)propyl)piperazin-1-yl)cyclohexyl)-3-methoxybenzamide (trans) (Compound 3) To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (78.56 mg, 184.64 μmol) in DMF (1 mL) was added HATU (105.31 mg, 276.95 μmol) and DIPEA (119.31 mg, 923.18 μmol, 160.80 μL). The mixture was stirred at 25° C. for 0.5 h. Then, 3-((4-(3-(4-((1r,4r)-4-aminocyclohexyl)piperazin-1-yl)propyl)phenyl)amino)piperidine-2,6-dione (trans) (0.1 g, 184.64 μmol, TFA) was added to the mixture and stirred at 25° C. for an additional 16 h. LCMS confirmed complete consumption of 3-((4-(3-(4-((1r,4r)-4-aminocyclohexyl)piperazin-1-yl)propyl)phenyl)amino)piperidine-2,6-dione (trans) and a peak of the desired mass was detected. The reaction mixture was quenched with HO (10 mL) at 25 °C and extracted with EtOAc (80 mL). The combined organic layers were washed with brine (10 mL), dried over NaSO, filtered, and concentrated in vacuo to give a residue. The residue was purified by flash silica gel chromatography (ISCO®; 20 g SepaFlash® silica flash column, eluent 0-30% MeOH / EtOAc 50 mL / min) to give the title compound (91.6 mg, 104.21 μmol, 56.44% yield, 95% purity) as a white solid. MS (M+H) + =835.4.

[0123] [ka]

[0124] Example 4 Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(4-((2,6-dioxopiperidin-3-yl)amino)phenethyl)piperazin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 4)

[0125] [ka]

[0126] Step 1. Synthesis of 4-(2-((tert-butyldimethylsilyl)oxy)ethyl)aniline (2) To a solution of 2-(4-aminophenyl)ethan-1-ol (2 g, 14.58 mmol) in DCM (20 mL) were added TBSCl (2.7 g, 17.91 mmol, 2.2 mL) and imidazole (1.2 g, 17.63 mmol), and the mixture was stirred at 25 °C for 14 h. TLC (petroleum ether: EtOAc = 5:1) revealed a new spot. The mixture was diluted with water (20 mL) and extracted with EtOAc (20 mL x 2). The combined organic layers were concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (20 g SepaFlash® silica flash column, eluent: 20-30% EtOAc / MeOH gradient @ 50 mL / min) to afford the title compound (4.27 g, crude) as a yellow oil. MS (M+H) + =252.4

[0127] Step 2. Synthesis of 3-((4-(2-((tert-butyldimethylsilyl)oxy)ethyl)phenyl)amino)piperidine-2,6-dione (4) To a solution of 4-[2-[tert-butyl(dimethyl)silyl]oxyethyl]aniline (2 g, 7.95 mmol) and 3-bromopiperidine-2,6-dione (2.29 g, 11.93 mmol) in ACN (40 mL) at 20 °C, DIPEA (3.08 g, 23.86 mmol, 4.16 mL) was added and stirred at 80 °C for 12 h. LCMS confirmed that 44% of 4-(2-((tert-butyldimethylsilyl)oxy)ethyl)aniline remained, and a peak of the desired mass (38%) was detected. The mixture was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (ISCO®; 20 g SepaFlash® silica flash column, eluent: 0-25% EtOAc / petroleum ether gradient @ 200 mL / min) to afford the title compound (806 mg, 2.22 mmol, 27.95% yield) as a brown solid. MS (M+H) + =363.3

[0128] Step 3. Synthesis of 3-((4-(2-hydroxyethyl)phenyl)amino)piperidine-2,6-dione (5) To a solution of 3-[4-[2-[tert-butyl(dimethyl)silyl]oxyethyl]anilino]piperidine-2,6-dione (400 mg, 1.10 mmol) in dioxane (5 mL) was added HCl / dioxane (4 M, 10 mL) at 20° C. and stirred at 20° C. for 1 hour. LCMS confirmed complete consumption of the starting material, and a peak of the desired mass was detected. The mixture was combined with another batch (200 mg). The mixture was concentrated to give the title compound (600 mg, crude) as a brown solid. MS (M+H) + =249.2

[0129] Step 4. Synthesis of 4-((2,6-dioxopiperidin-3-yl)amino)phenethyl 4-methylbenzenesulfonate (6) To a solution of 3-((4-(2-hydroxyethyl)phenyl)amino)piperidine-2,6-dione (600 mg, 2.42 mmol) in DCM (8 mL) at 20 °C, TEA (733.62 mg, 7.25 mmol, 1.01 mL) and TosCl (691.09 mg, 3.62 mmol) were added. The mixture was stirred at 20 °C for 12 h. LCMS confirmed complete consumption of the starting material, and a peak of the desired mass (58%) was detected. The mixture was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, eluent: 0-50% EtOAc / petroleum ether gradient @ 100 mL / min) to afford the title compound (332 mg, 824.92 μmol, 34.13% yield) as a blue solid. MS (M+H) + =403.2

[0130] Step 5. Synthesis of tert-butyl ((1r,4r)-4-(4-(4-((2,6-dioxopiperidin-3-yl)amino)phenethyl)piperazin-1-yl)cyclohexyl)carbamate (trans) (8) To a solution of 4-((2,6-dioxopiperidin-3-yl)amino)phenethyl 4-methylbenzenesulfonate (332 mg, 824.92 μmol) and tert-butyl ((1r,4r)-4-(piperazin-1-yl)cyclohexyl)carbamate (trans) (467.58 mg, 1.65 mmol) in DMF (10 mL) at 20 °C was added DIPEA (639.68 mg, 4.95 mmol, 862.10 μL) and NaI (24.73 mg, 164.98 μmol). The mixture was stirred at 40 °C for 12 h. LCMS confirmed that 26% of 4-((2,6-dioxopiperidin-3-yl)amino)phenethyl 4-methylbenzenesulfonate remained, and a peak with the desired mass (25%) was detected. The reaction mixture was diluted with H2O (40 mL) and extracted with EtOAc (20 mL x 3). The organic layer was washed with brine (15 mL x 3), dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by prep-TLC (SiO2, DCM:MeOH = 10:1) and then repurified by reverse-phase HPLC (column: Phenomenex luna C18 150 x 25 mm x 10 μm; mobile phase: [water (TFA)-ACN]; B%: 14%-44%, 9 min) and lyophilized to give the title compound (220 mg, 332.96 μmol, 40.36% yield, 95% purity, TFA). MS (M+H) + =514.5

[0131] Step 6. Synthesis of 3-((4-(2-(4-((1r,4r)-4-aminocyclohexyl)piperazin-1-yl)ethyl)phenyl)amino)piperidine-2,6-dione (trans) (9) To a solution of tert-butyl ((1r,4r)-4-(4-(4-((2,6-dioxopiperidin-3-yl)amino)phenethyl)piperazin-1-yl)cyclohexyl)carbamate (trans) (220 mg, 428.29 μmol, TFA) in DCM (3 mL) at 20° C., TFA (460.50 mg, 4.04 mmol, 0.3 mL) was added and the mixture was stirred at 20° C. for 1 h. LCMS confirmed that the starting material had been consumed, and a peak of the desired mass (45%) was detected. The mixture was concentrated under reduced pressure to give the title compound (220 mg, crude, TFA) as a dark green oil. MS (M+H) + =414.4

[0132] Step 7. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(4-((2,6-dioxopiperidin-3-yl)amino)phenethyl)piperazin-1-yl)cyclohexyl)-3-methoxybenzamide (trans) (Compound 4) A solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (169.36 mg, 398.05 μmol) in DMF (4 mL) was treated with HATU (166.48 mg, 437.85 μmol) and DIPEA (308.67 mg, 2.39 mmol, 415.99 μL) at 20 °C. After stirring for 10 min, a solution of 3-((4-(2-(4-((1r,4r)-4-aminocyclohexyl)piperazin-1-yl)ethyl)phenyl)amino)piperidine-2,6-dione (trans) (210 mg, 398.05 μmol, TFA) in DMF (4 mL) and DIPEA (308.67 mg, 2.39 mmol, 415.99 μL) was added at 20 °C. The reaction mixture was stirred at 20 °C for 1 h. LCMS confirmed complete consumption of the starting material, and a peak corresponding to 37% of the desired mass was detected. The reaction mixture was diluted with HO (40 mL) and extracted with EtOAc (15 mL × 3). The combined organic phase was washed with brine (12 mL × 3), dried over NaSO, filtered, and concentrated under reduced pressure. The residue was purified by prep-TLC (SiO, DCM:MeOH = 10:1). The product was dissolved in a mixture (20 mL, ACN:H2O = 1:3) and lyophilized to give the title compound (82.6 mg, 96.38 μmol, 24.21% yield, 95.8% purity) as a white solid. MS (M+H) + =821.5

[0133] [ka]

[0134] Example 5 Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(2-((2-(2,6-dioxopiperidin-3-yl)-1-oxoisoindolin-4-yl)amino)ethyl)piperazin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 5)

[0135] [ka]

[0136] Step 1. Synthesis of benzyl 4-((1r,4r)-4-aminocyclohexyl)piperazine-1-carboxylate (trans) (2) To a solution of benzyl 4-((1r,4r)-4-((tert-butoxycarbonyl)amino)cyclohexyl)piperazine-1-carboxylate (trans) (1 g, 2.39 mmol) in DCM (5 mL) at 20 °C was added TFA (1.69 g, 14.86 mmol, 1.1 mL), and the resulting mixture was stirred at 20 °C for 1 h. LCMS confirmed that the starting material remained, and a peak with the desired mass was detected. To the mixture was added TFA (1.37 g, 11.97 mmol, 886.63 μL) at 20 °C, and the resulting mixture was stirred at 20 °C for 2 h. LCMS confirmed that the starting material remained, and a peak with the desired mass was detected. The reaction mixture was stirred at 20 °C for 12 h. LCMS confirmed that the starting material was completely consumed, and a peak with the desired mass was detected. The mixture was concentrated under reduced pressure to give the title compound (1.03 g, crude, TFA) as a yellow oil. MS (M+H) + =318.2

[0137] Step 2. Synthesis of benzyl 4-((1R,4r)-4-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamido)cyclohexyl)piperazine-1-carboxylate (trans) (4) To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (trans) (0.8 g, 1.88 mmol) in DMF (6 mL) was added HATU (786.41 mg, 2.07 mmol) and DIPEA (729.02 mg, 5.64 mmol, 982.51 μL) at 20 °C. After stirring for 10 min, a solution of benzyl 4-((1r,4r)-4-aminocyclohexyl)piperazine-1-carboxylate (1.03 g, crude, TFA) in DMF (6 mL) and DIPEA (1.46 g, 11.28 mmol, 1.97 mL) was added at 20 °C, and the resulting mixture was stirred at 20 °C for 1 h. LCMS confirmed complete consumption of all starting material, and a peak corresponding to 78% of the desired mass was detected. The reaction mixture was diluted with HO (20 mL) and extracted with EtOAc (20 mL x 3). The organic layer was washed with brine (20 mL x 3), dried over NaSO, filtered, and concentrated. The residue was purified by flash silica gel chromatography (25 g SepaFlash® silica flash column, eluent: 0-100% EtOAc / petroleum ether to 0-15% DCM / MeOH gradient @ 200 mL / min) to afford the title compound (1.2 g, 1.64 mmol, 87.17% yield, 99% purity) as an off-white solid. MS (M+H) + =725.4

[0138] Step 3. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-((1r,4R)-4-(piperazin-1-yl)cyclohexyl)benzamide (trans) (5) A solution of benzyl 4-((1R,4r)-4-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamido)cyclohexyl)piperazine-1-carboxylate (trans) (600.00 mg, 827.71 μmol) in TFA (7.68 g, 67.31 mmol, 5 mL) was stirred at 50° C. for 12 hours. LCMS confirmed complete consumption of the starting material, with a peak corresponding to 84% of the desired mass. The mixture was concentrated under reduced pressure to give the title compound (583 mg, crude, TFA) as a brown oil. MS (M+H) + =591.4

[0139] Step 4. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(2,2-dimethoxyethyl)piperazin-1-yl)cyclohexyl)-3-methoxybenzamide (trans) (6) To a solution of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-((1r,4R)-4-(piperazin-1-yl)cyclohexyl)benzamide (trans) (523.00 mg, crude, TFA) in DMF (10 mL) at 20 °C was added DIPEA (575.43 mg, 4.45 mmol, 775.52 μL) and 2-bromo-1,1-dimethoxyethane (224.51 mg, 1.33 mmol, 155.91 μL), and the resulting mixture was stirred at 100 °C for 12 h. LCMS showed 3% starting material remaining, with the desired mass peak (27%) detected. The mixture was diluted with H2O (20 mL) and extracted with EtOAc (15 mL x 3). The organic layer was washed with brine (15 mL x 3), dried over Na2SO4, filtered, and concentrated. The residue was purified by flash silica gel chromatography (10 g SepaFlash® silica flash column, eluent: 0-100% EtOAc / petroleum ether gradient @ 150 mL / min) to afford the title compound (283 mg, 416.87 μmol, 56.18% yield) as a yellow solid. MS (M+H) + =679.4

[0140] Step 5. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-((1r,4R)-4-(4-(2-oxoethyl)piperazin-1-yl)cyclohexyl)benzamide (trans) (7) To a solution of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(2,2-dimethoxyethyl)piperazin-1-yl)cyclohexyl)-3-methoxybenzamide (trans) (283 mg, 416.87 μmol) in HO (5 mL) at 20 °C was added HBr (1.49 g, 7.37 mmol, 1 mL, 40% purity), and the resulting mixture was stirred at 40 °C for 12 h. LCMS confirmed the remaining starting material (42%) and the desired mass peak (28%) was detected, so the reaction mixture was stirred at 40 °C for 12 h. LCMS confirmed the complete consumption of the starting material and the desired mass peak (91%) was detected. The mixture was concentrated under reduced pressure to give the title compound (264 mg, crude) as a yellow oil. MS (M+H2O+H) + =651.3

[0141] Step 6. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(2-((2-(2,6-dioxopiperidin-3-yl)-1-oxoisoindolin-4-yl)amino)ethyl)piperazin-1-yl)cyclohexyl)-3-methoxybenzamide (trans) (Compound 5) To a solution of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-((1r,4R)-4-(4-(2-oxoethyl)piperazin-1-yl)cyclohexyl)benzamide (trans) (174 mg, 274.97 μmol), 3-(4-amino-1-oxo-isoindolin-2-yl)piperidine-2,6-dione (71.29 mg, 274.97 μmol) in MeOH (5 mL) was added TFA (31.35 mg, 274.97 μmol, 20.43 μL) at 20° C., followed by slow addition of NaBHCN (51.84 mg, 824.91 μmol) at 20° C. and stirring at 20° C. for 1 hour. LCMS confirmed complete consumption of the starting material, and a peak of the desired mass (55%) was detected. The mixture was concentrated under reduced pressure. The residue was diluted with H2O (15 mL) and extracted with EtOAc (10 mL x 3). The organic layer was washed with saturated NaHCO3 solution (10 mL x 3), dried over Na2SO4, filtered, and concentrated. The residue was purified by prep-TLC (SiO2, DCM:MeOH = 10:1) to give the product, which was confirmed to be 85% pure by LCMS. The product was repurified by prep-HPLC (column: Phenomenex luna C18 150 x 40 mm x 15 μm; mobile phase: [water (TFA)-ACN]; B%: 15%-45%, 10 min) and lyophilized to give the title compound (23.1 mg, 18.58 μmol, 6.76% yield, 98% purity, 3 TFA) as a white solid. MS(M+H) + =876.4

[0142] [ka]

[0143] Example 6 Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((2-(2,6-dioxopiperidin-3-yl)-1-oxoisoindolin-4-yl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 6)

[0144] [ka]

[0145] Step 1. Synthesis of tert-butyl 4-(((2-(2,6-dioxopiperidin-3-yl)-1-oxoisoindolin-4-yl)amino)methyl)piperidine-1-carboxylate (3) To a solution of 3-(4-amino-1-oxoisoindolin-2-yl)piperidine-2,6-dione (1 g, 3.86 mmol) and tert-butyl 4-formylpiperidine-1-carboxylate (904.88 mg, 4.24 mmol) in MeOH (20 mL) was added HOAc (115.81 mg, 1.93 mmol, 110.40 μL), TFA (87.96 mg, 771.43 μmol, 57.30 μL), and NaBHCN (727.17 mg, 11.57 mmol). The mixture was stirred at 25 °C for 16 h. LCMS showed 45% of 3-(4-amino-1-oxoisoindolin-2-yl)piperidine-2,6-dione remaining and several new peaks, with the desired mass (44%) detected. The mixture was quenched with aqueous NaHCO (30 mL) at 0 °C and extracted with EtOAc (50 mL × 2). The combined organic phases were washed with brine (30 mL), dried over NaSO, filtered, and concentrated under reduced pressure to give a residue that was triturated with EtOAc at 25 °C for 2 h and with MeOH at 25 °C for 16 h to give the title compound (780 mg, 1.25 mmol, 32.34% yield, 73% purity) as a white solid. MS (M+H-100) + =357.3

[0146] Step 2. Synthesis of 3-(1-oxo-4-((piperidin-4-ylmethyl)amino)isoindolin-2-yl)piperidine-2,6-dione (4) To a solution of tert-butyl 4-(((2-(2,6-dioxopiperidin-3-yl)-1-oxoisoindolin-4-yl)amino)methyl)piperidine-1-carboxylate (780 mg, 1.25 mmol) in dioxane (2 mL) was added HCl / dioxane (4 M, 3.12 mL). The mixture was stirred at 20° C. for 2 hours. LCMS confirmed complete consumption of tert-butyl 4-(((2-(2,6-dioxopiperidin-3-yl)-1-oxoisoindolin-4-yl)amino)methyl)piperidine-1-carboxylate, and a peak of the desired mass (65%) was detected. The mixture was concentrated under reduced pressure to remove the solvent. The residue was purified by prep-HPLC (column: YMC Triart C18 150*25mm*5um; mobile phase: [water(HCl)-ACN]; B%: 4%-34%, 10 min) and lyophilized to give the title compound (360 mg, 916.31 μmol, 73.47% yield, HCl) as a white solid. MS (M+H) + =357.1

[0147] Step 3. Synthesis of tert-butyl ((1r,4r)-4-(4-(((2-(2,6-dioxopiperidin-3-yl)-1-oxoisoindolin-4-yl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (6) To a solution of 3-(1-oxo-4-((piperidin-4-ylmethyl)amino)isoindolin-2-yl)piperidine-2,6-dione (340 mg, 865.41 μmol, HCl) and tert-butyl ((1s,4s)-4-iodocyclohexyl)carbamate (562.83 mg, 1.73 mmol) in ACN (3 mL) and DMF (3 mL) was added NaCO (550.35 mg, 5.19 mmol). The mixture was stirred at 80 °C for 16 h. LCMS confirmed 38% of 3-(1-oxo-4-((piperidin-4-ylmethyl)amino)isoindolin-2-yl)piperidine-2,6-dione remaining, plus several new peaks, and the desired mass (28%) was detected. Additional tert-butyl ((1s,4s)-4-iodocyclohexyl)carbamate (281.42 mg, 865.41 μmol) was added. The mixture was stirred at 80° C. for 32 h. LCMS confirmed that 3-(1-oxo-4-((piperidin-4-ylmethyl)amino)isoindolin-2-yl)piperidine-2,6-dione remained (16%), and a peak of the desired mass (30%) was detected. The mixture was quenched with water (10 mL) at 0° C. and extracted with EtOAc (50 mL×2). The combined organic phase was washed with brine (15 mL), dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 40 mm x 15 μm; mobile phase: [water(FA)-ACN]; gradient: 8%-38% B over 15 min) and lyophilized to give the title compound (60 mg, 105.11 μmol, 12.15% yield, 97% purity) as a white solid. MS (M+H) + =554.5

[0148] Step 4. Synthesis of 3-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)-1-oxoisoindolin-2-yl)piperidine-2,6-dione (7) To a solution of tert-butyl ((1r,4r)-4-(4-(((2-(2,6-dioxopiperidin-3-yl)-1-oxoisoindolin-4-yl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (40 mg, 72.24 μmol) in dioxane (0.2 mL) was added HCl / dioxane (4 M, 180.61 μL). The mixture was stirred at 20° C. for 0.5 h. LCMS confirmed complete consumption of the starting material, with one main peak of the desired mass. The mixture was concentrated to afford the title compound (35 mg, 71.42 μmol, 98.87% yield, HCl) as a white solid. MS (M+H) + =454.3

[0149] Step 5. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((2-(2,6-dioxopiperidin-3-yl)-1-oxoisoindolin-4-yl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 6) To a solution of 3-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)-1-oxoisoindolin-2-yl)piperidine-2,6-dione (35 mg, 71.42 μmol, HCl), (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (27.35 mg, 64.28 μmol) in DMF (2 mL) was added HATU (40.74 mg, 107.13 μmol) and DIPEA (46.15 mg, 357.12 μmol, 62.20 μL). The mixture was stirred at 20° C. for 16 h. LCMS confirmed the consumption of the starting material, and a peak of the desired mass (60%) was detected. The mixture was quenched with water (15 mL) at 0 °C and extracted with EtOAc (20 mL × 2). The combined organic phase was washed with brine (10 mL), dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex luna C18 150 × 25 mm × 10 μm; mobile phase: [water (TFA)-ACN]; gradient: 30%-60% B over 10 min) and lyophilized to give the title compound (29.0 mg, 25.83 μmol, 36.16% yield, 97% purity, 2% TFA) as a white solid. MS (M+H) + =861.5

[0150] [ka]

[0151] Example 7 Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)benzyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 7)

[0152] [ka]

[0153] Step 1. Synthesis of (4-(2,6-bis(benzyloxy)pyridin-3-yl)phenyl)methanol (3) To a solution of 2,6-bis(benzyloxy)-3-bromopyridine (2 g, 5.40 mmol), (4-(hydroxymethyl)phenyl)boronic acid (902.93 mg, 5.94 mmol) in dioxane (20 mL) and water (2 mL), Pd(dppf)Cl (395.26 mg, 540.19 μmol), and KCO (2.24 g, 16.21 mmol) were added and stirred at 100 °C under N for 16 h. LCMS showed a main peak corresponding to the desired mass. The mixture was filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (20 g SepaFlash® silica flash column, eluent: 0–50% EtOAc / petroleum ether gradient @ 40 mL / min) to afford the title compound (1.8 g, 4.53 mmol, 83.84% yield) as a yellow oil. MS(M+H) + =398.2.

[0154] Step 2. Synthesis of 3-(4-(hydroxymethyl)phenyl)piperidine-2,6-dione (4) A solution of (4-(2,6-bis(benzyloxy)pyridin-3-yl)phenyl)methanol (1 g, 2.52 mmol) and Pd / C (200 mg, 2.52 mmol, 10% purity) in CF3CH2OH (10 mL) was degassed and purged with H2 three times, then stirred at 30 °C under H2 (50 Psi) for 16 h. TLC (petroleum ether: EtOAc = 1:2) confirmed complete consumption of the starting material, and a new, more polar spot was detected. The mixture was filtered, and the filter cake was washed with CF3CH2OH (100 mL). The filtered material was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (Biotage; 10 g SepaFlash® silica flash column, eluent: 0-50% EtOAc / petroleum ether gradient @ 80 mL / min) to afford the title compound (300 mg, 1.37 mmol, 54.63% yield) as a white solid. MS (M+H) + =219.3.

[0155] Step 3. Synthesis of 4-(2,6-dioxopiperidin-3-yl)benzaldehyde (5) To a solution of 3-(4-(hydroxymethyl)phenyl)piperidine-2,6-dione (100 mg, 458.19 μmol) in DCM (2 mL) was added MnO (199.17 mg, 2.29 mmol) and stirred at 20 °C for 16 h. TLC (petroleum ether: EtOAc = 1:2) confirmed complete consumption of the starting material, and one new main spot was detected. The mixture was filtered, and the filter cake was washed with DCM (20 mL). The residue was concentrated to give the title compound (50 mg, 230.18 μmol, 50.24% yield) as a yellow solid. MS (M+H) + =218.3.

[0156] Step 4. Synthesis of benzyl (4-(4-(((tert-butoxycarbonyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (11) To a solution of tert-butyl (piperidin-4-ylmethyl)carbamate (3 g, 14.00 mmol) in DCE (80 mL) was added benzyl (4-oxocyclohexyl)carbamate (3.5 g, 14.15 mmol) and HOAc (840.66 mg, 14.00 mmol, 801.39 μL) at 20 °C. After stirring at 25 °C for 2 h, NaBH(OAc) (11.87 g, 56.00 mmol) was added and stirred at 25 °C for 14 h. LCMS showed the main peak corresponding to the desired mass. The reaction mixture was quenched by adding NaHCO (200 mL) solution and then extracted with EtOAc (200 mL × 3). The combined organic phase was washed with brine (500 mL × 2), dried over NaSO, filtered, and concentrated under reduced pressure. The residue was subjected to reverse phase HPLC (column 330 g Flash Column Welch Ultimate XB_C 18 20-40 μm; 120A; Sample dissolution solvent: Dissolve approximately 15.00 g of sample in 20 mL of DMF; Flow rate: 100 mL / min; Mobile phase: MeCN / H2O; Gradient: 10-100% B in 50 min; % min; Instrument: TELEDYNE ISCO CombiFlashRf 150 The eluate was lyophilized to give the title compound (2 g, 4.49 mmol, 32.06% yield) as a yellow solid. MS (M+H) + =446.3.

[0157] Step 5. Synthesis of benzyl ((1r,4r)-4-(4-(((tert-butoxycarbonyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (trans) (12) To a solution of benzyl (4-(4-(((tert-butoxycarbonyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (0.5 g, 1.12 mmol) in CH3CN (15 mL) was added (S)-5-oxopyrrolidine-2-carboxylic acid (75.00 mg, 580.88 μmol) at 25 °C. The mixture was stirred at 70 °C for 2 h, then at 25 °C for 16 h. A main peak of the desired mass was detected by LCMS. The mixture was filtered. The filter cake was diluted with EtOAc (30 mL) and HO (15 mL), and the mixture was adjusted to pH = 8 with NaOH (1 M, 0.5 mL) solution and extracted with EtOAc (40 mL × 2). The combined organic phase was washed with brine (30 mL x 2), dried over Na2SO4, filtered, and concentrated under reduced pressure to give the title compound (180 mg, 403.96 μmol, 36.00% yield) as a white solid. MS (M+H) + =446.3.

[0158] Step 6. Synthesis of benzyl ((1r,4r)-4-(4-(aminomethyl)piperidin-1-yl)cyclohexyl)carbamate (trans) (6) To a solution of benzyl ((1r,4r)-4-(4-(((tert-butoxycarbonyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (trans) (180 mg, 403.96 μmol) in dioxane (1 mL) was added HCl / dioxane (4 M, 1 mL) and stirred at 20°C for 1 hour. LCMS confirmed the main peak of the desired mass. The mixture was concentrated to give the title compound (150 mg, crude, HCl salt) as a white solid. MS (M+H) + =346.2.

[0159] Step 7. Synthesis of benzyl ((1r,4r)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)benzyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (trans) (7) To a solution of 4-(2,6-dioxopiperidin-3-yl)benzaldehyde (50 mg, 230.18 μmol), benzyl ((1r,4r)-4-(4-(aminomethyl)piperidin-1-yl)cyclohexyl)carbamate (trans) (87.92 mg, 230.18 μmol, HCl salt) in DCM (2 mL) was added NaOAc (18.88 mg, 230.18 μmol) at 20 °C. After stirring for 0.5 h, NaBH(OAc) (146.35 mg, 690.54 μmol) was added, and the mixture was stirred at 20 °C for 16 h. LCMS showed the main peak of the desired mass. The mixture was diluted with water (10 mL) and extracted with EtOAc (10 mL × 3). The combined organic phase was washed with NaHCO3 (10 mL x 2), dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by reverse-phase HPLC (column: YMC Triart C18 150 x 25 mm x 5 μm; mobile phase: [water(HCl)-ACN]; gradient: 2%-32% B over 8 min). The eluate was lyophilized to afford the title compound (60 mg, 109.75 μmol, 47.68% yield) as a white solid. MS (M+H) + =547.4.

[0160] Step 8. Synthesis of 3-(4-((((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)methyl)phenyl)piperidine-2,6-dione (trans) (8) A mixture of benzyl ((1r,4r)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)benzyl)amino)methyl)piperidin-1-yl)cyclohexyl)carbamate (trans) (60 mg, 109.75 μmol) in TFA (1 mL) was stirred at 60° C. for 4 hours. LCMS showed a main peak of the desired mass. The mixture was concentrated under reduced pressure to give the title compound (57 mg, 108.24 μmol, 98.63% yield, TFA salt) as a brown oil. MS (M+H) + =413.3.

[0161] Step 9. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((4-(2,6-dioxopiperidin-3-yl)benzyl)amino)methyl)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (trans) (Compound 7) To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (40.40 mg, 94.95 μmol) in DMF (1 mL) was added HATU (54.15 mg, 142.43 μmol) and DIPEA (61.36 mg, 474.75 μmol, 82.69 μL) at 20° C. After stirring for 0.5 h, 3-(4-((((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)methyl)amino)methyl)phenyl)piperidine-2,6-dione (trans) (50 mg, 94.95 μmol, TFA salt) was added to the mixture, and the reaction mixture was stirred at 20° C. for 16 h. LCMS showed a main peak of the desired mass. The mixture was diluted with water (10 mL) and extracted with EtOAc (10 mL x 3). The combined organic phase was washed with brine (20 mL x 2), dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by reverse-phase HPLC (column: Phenomenex luna C18 150 x 25 mm x 10 μm; mobile phase: [water (TFA)-ACN]; gradient: 22%-52% B over 10 min). The eluate was lyophilized to give the title compound (42.4 mg, 37.62 μmol, 39.62% yield, 93% purity, di-TFA salt) as a white solid. MS (M+H) + =820.5.

[0162] [ka]

[0163] Example 8 Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-((4-(2,6-dioxopiperidin-3-yl)benzyl)amino)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 8)

[0164] [ka]

[0165] Step 1. Synthesis of tert-butyl (4-(2,6-bis(benzyloxy)pyridin-3-yl)benzyl)carbamate (3) To a solution of tert-butyl (4-bromobenzyl)carbamate (450 mg, 1.57 mmol), 2,6-bis(benzyloxy)-3-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)pyridine (656.22 mg, 1.57 mmol) in dioxane (5 mL) and HO (0.5 mL) was added Pd(dppf)Cl (230.12 mg, 314.50 μmol), and KCO (651.99 mg, 4.72 mmol). The mixture was stirred at 100 °C under N for 16 h. LCMS showed a peak corresponding to the desired mass (53%). The mixture was filtered through a pad of Celite. The filtrate was concentrated to give the residue. The residue was purified by flash silica gel chromatography (Biotage; 10 g SepaFlash® silica flash column, eluent: 0-20% EtOAc / petroleum ether gradient @ 80 mL / min) to afford the title compound (600 mg, 1.12 mmol, 71.46% yield, 93% purity) as a yellow solid. MS (M+H) + =497.2.

[0166] Step 2. Synthesis of tert-butyl (4-(2,6-dioxopiperidin-3-yl)benzyl)carbamate (4) A mixture of tert-butyl (4-(2,6-bis(benzyloxy)pyridin-3-yl)benzyl)carbamate (600 mg, 1.21 mmol) and Pd / C (100 mg, 10% purity) in CF3CH2OH (10 mL) was degassed, purged with H2 three times, and then stirred at 20 °C under H2 (50 Psi) for 16 h. TLC (petroleum ether: EtOAc = 3:1) confirmed complete consumption of the starting material, and a new, less polar spot was detected. The mixture was diluted with CH3CH2OH (30 mL), filtered through a pad of Celite, and washed with CH3CH2OH (30 mL). The residue was concentrated to give the title compound (380 mg, 1.19 mmol, 98.79% yield) as a yellow oil. MS (M+H) + =319.4.

[0167] Step 3. Synthesis of 3-(4-(aminomethyl)phenyl)piperidine-2,6-dione (5) To a solution of tert-butyl (4-(2,6-dioxopiperidin-3-yl)benzyl)carbamate (280 mg, 879.49 μmol) in dioxane (3 mL), HCl / dioxane (4 M, 2.80 mL) was added and stirred at 20°C for 1 h. TLC (petroleum ether: EtOAc = 3:1) confirmed complete consumption of the starting material, and one new major spot was detected at a less polar position. The mixture was concentrated under reduced pressure to give the title compound (220 mg, crude, HCl) as a white solid. MS (M+H) + =219.3.

[0168] Step 4. Synthesis of benzyl ((1r,4r)-4-(4-oxopiperidin-1-yl)cyclohexyl)carbamate (6) To a solution of benzyl ((1r,4r)-4-aminocyclohexyl)carbamate (500 mg, 1.76 mmol, HCl) in MeOH (5 mL), 1,5-dichloropentan-3-one (272.18 mg, 1.76 mmol) and NaHCO (737.47 mg, 8.78 mmol, 341.58 μL) were added and stirred at 75 °C for 16 h. LCMS showed a major peak and a peak of the desired mass. TLC (DCM:MeOH = 10:1) confirmed the consumption of the starting material, and a new spot was detected. The mixture was diluted with H O (10 mL) and extracted with EtOAc (10 mL × 3). The combined organic phase was washed with brine (20 mL × 2), dried over Na SO , and filtered. The filtrate was concentrated to give the residue. The residue was purified by flash silica gel chromatography (Biotage; 10 g SepaFlash® silica flash column, eluent: 50-100% EtOAc / petroleum ether to 10% MeOH / EtOAc gradient @ 80 mL / min) to afford the title compound (400 mg, 1.21 mmol, 68.95% yield) as a yellow oil. MS (M+H) + =331.1.

[0169] Step 5. Synthesis of benzyl ((1r,4r)-4-(4-((4-(2,6-dioxopiperidin-3-yl)benzyl)amino)piperidin-1-yl)cyclohexyl)carbamate (7) To a solution of 3-(4-(aminomethyl)phenyl)piperidine-2,6-dione (80 mg, crude, HCl) and benzyl ((1r,4r)-4-(4-oxopiperidin-1-yl)cyclohexyl)carbamate (103.78 mg, 314.08 μmol) in DCM (1 mL) was added TEA (158.91 mg, 1.57 mmol, 218.58 μL), and the mixture was stirred at 20 °C for 0.5 h. NaBH(OAc) (199.70 mg, 942.24 μmol) was added, and the mixture was stirred at 20 °C for 16 h. LCMS showed a main peak corresponding to the desired mass. The mixture was filtered, and the filter cake was washed twice with EtOAc (10 mL) and water (10 mL), followed by drying under reduced pressure to give the title compound (150 mg, crude) as a white solid. MS(M+H) + =533.4.

[0170] Step 6. Synthesis of 3-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)amino)methyl)phenyl)piperidine-2,6-dione (8) A mixture of benzyl ((1r,4r)-4-(4-((4-(2,6-dioxopiperidin-3-yl)benzyl)amino)piperidin-1-yl)cyclohexyl)carbamate (100 mg, crude) in TFA (0.5 mL) was stirred at 60° C. for 4 hours. LCMS showed the main peak of the desired mass. The mixture was concentrated to give the title compound (90 mg, crude, TFA) as a brown oil. MS (M+H) + =399.3.

[0171] Step 7. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-((4-(2,6-dioxopiperidin-3-yl)benzyl)amino)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 8) To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (74.71 mg, 175.59 μmol) in DMF (2 mL) was added HATU (80.12 mg, 210.71 μmol) and DIPEA (68.08 mg, 526.76 μmol, 91.75 μL), and the mixture was stirred at 20° C. for 0.5 h. To the mixture was added 3-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)amino)methyl)phenyl)piperidine-2,6-dione (90 mg, crude, TFA), and the mixture was stirred at 20° C. for 16 h. LCMS showed the desired mass peak (47%). The mixture was diluted with water (10 mL) and extracted with EtOAc (10 mL × 3). The combined organic phase was washed with brine (20 mL × 2), dried over Na2SO4, and filtered. The filtrate was concentrated under reduced pressure to give the residue. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 × 25 mm × 10 μm; mobile phase: [water (TFA)-ACN]; gradient: 23%-53% B over 10 min) and then repurified by prep-HPLC (column: Phenomenex Luna C18 150 × 25 mm × 10 μm; mobile phase: [water (TFA)-ACN]; gradient: 22%-52% B over 10 min). The eluate was lyophilized to give the title compound (41.5 mg, 40.13 μmol, 22.86% yield, 98% purity, 2% TFA) as a white solid. MS (M+H) + =806.5.

[0172] [ka]

[0173] Example 9 Synthesis of N-(1-(2-amino-3-(4-(2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4-yl)piperazin-1-yl)propanoyl)piperidin-4-yl)-4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamide (Compound 9)

[0174] [ka]

[0175] Step 1. Synthesis of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (13) Three batches: A mixture of (R)-2-chloro-8-cyclopentyl-7-ethyl-5-methyl-7,8-dihydropteridin-6(5H)-one (550 mg, 1.87 mmol), 4-amino-3-methoxybenzoic acid (374.27 mg, 2.24 mmol), and HCl (12 M, 550.00 μL) in EtOH (2 mL) and water (8 mL) was stirred for 12 h at 105° C. LCMS confirmed complete consumption of (R)-2-chloro-8-cyclopentyl-7-ethyl-5-methyl-7,8-dihydropteridin-6(5H)-one. Three batches were concentrated under reduced pressure to give a mixture of (R)-ethyl 4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoate and (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (2.5 g) in the form of a brown gum. To a solution of the brown gum (2.5 g) in MeOH (20 mL) and THF (20 mL) was added NaOH (2 M, 20 mL), and the mixture was stirred at 25° C. for 16 hours. LCMS confirmed complete consumption of the starting material, with a peak corresponding to 65% of the desired mass. The mixture was concentrated under reduced pressure to remove the solvent. The residue was triturated with HO (30 mL) and EtOAc (30 mL) for 10 min, the suspension was filtered, the filter cake was washed with HO (30 mL) and EtOAc (30 mL), the filter cake was diluted with EtOH (30 mL) and HCl solution (20 mL), the mixture was concentrated under reduced pressure at 70 °C, the residue was triturated with a mixture (EtOAc:EtOH:DMF = 4:2:1, 7 mL) for 30 min, the suspension was filtered, the filter cake was washed with EtOAc (20 mL), and the mixture was triturated again with a mixture (EtOAc:EtOH:DMF = 4:2:1, 10 mL) for 30 min, the suspension was filtered, the filter cake was washed with a mixture (EtOAc:EtOH:DMF = 4:2:1, 3 mL), and the filter cake was dried to give the title compound (950 mg, 2.23 mmol, 78.51% yield) as a gray solid. MS(M+H) + =426.2.

[0176] [ka]

[0177] Step 2. Synthesis of tert-butyl (R)-4-(4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamido)piperidine-1-carboxylate (15) To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (400 mg, 940.12 μmol) in DMF (5 mL) was added HATU (428.95 mg, 1.13 mmol) and DIPEA (364.51 mg, 2.82 mmol). After stirring at 25° C. for 15 min, tert-butyl 4-aminopiperidine-1-carboxylate (188.28 mg, 940.12 μmol) was added to the mixture, and the resulting mixture was stirred at 25° C. for 1 h. LCMS confirmed complete consumption of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid, and a peak corresponding to 75% of the desired mass was detected. The mixture was adjusted to pH 6-7 with AcOH, and the resulting mixture was diluted with HO (50 mL) and extracted with EtOAc (50 mL x 3). The combined organic phase was washed with brine (100 mL x 3), dried over NaSO, filtered, and concentrated under reduced pressure. The residue was purified by prep-TLC (SiO, petroleum ether: EtOAc = 1:2) to give the title compound (375 mg, 617.04 μmol, 65.63% yield) as an off-white solid. MS (M+H) + =608.3.

[0178] Step 3. Synthesis of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(piperidin-4-yl)benzamide (8) To a solution of tert-butyl (R)-4-(4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamido)piperidine-1-carboxylate (400 mg, 658.17 μmol) in DCM (10 mL) was added HCl / dioxane (4 M, 10 mL), and the mixture was stirred at 25° C. for 1 h. LCMS confirmed complete consumption of the starting material, with a peak corresponding to 89% of the desired mass. The mixture was concentrated under reduced pressure to afford the title compound (395 mg, HCl salt) as an off-white solid. MS (M+H) + =508.2.

[0179] Step 4. Synthesis of benzyl 4-(2-((tert-butoxycarbonyl)amino)-3-methoxy-3-oxopropyl)piperazine-1-carboxylate (3) A mixture of methyl 2-((tert-butoxycarbonyl)amino)-3-iodopropanoate (2.5 g, 7.60 mmol), benzylpiperazine-1-carboxylate (1.71 g, 7.75 mmol, 1.50 mL), and Na2CO3 (1.61 g, 15.19 mmol) in acetone (50 mL) was stirred at 25 °C for 12 h. LCMS confirmed complete consumption of methyl 2-((tert-butoxycarbonyl)amino)-3-iodopropanoate, and a peak corresponding to 33% of the desired mass was detected. The suspension was filtered, and the filter cake was washed with EtOAc (50 mL), and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (20 g SepaFlash® silica flash column, eluent: 14-26% EtOAc / petroleum ether gradient @ 100 mL / min) to afford the title compound (1.07 g, 2.54 mmol, 33.42% yield) as a yellow oil. MS (M+H) + =422.2.

[0180] Step 5. Synthesis of 3-(4-((benzyloxy)carbonyl)piperazin-1-yl)-2-((tert-butoxycarbonyl)amino)propanoic acid (4) To a solution of benzyl 4-(2-((tert-butoxycarbonyl)amino)-3-methoxy-3-oxopropyl)piperazine-1-carboxylate (1.07 g, 2.54 mmol) in MeOH (5 mL) and THF (5 mL) was added NaOH (2 M, 5 mL), and the mixture was stirred at 25 °C for 12 h. LCMS confirmed complete consumption of the starting material, and a peak corresponding to 53% of the desired mass was detected. The mixture was concentrated under reduced pressure to remove the solvent. The residue was adjusted to pH 5-6 with a mixture of AcOH (580 μL) in water (5 mL) at 0 °C. The mixture was extracted with EtOAc (10 mL x 2), and the combined organic phase was concentrated under reduced pressure to give the title compound (850 mg) as a brown oil, which was used immediately in the next step. MS (M+H) + =408.2.

[0181] Step 6. Synthesis of 2-((tert-butoxycarbonyl)amino)-3-(piperazin-1-yl)propanoic acid (5) To a solution of 3-(4-((benzyloxy)carbonyl)piperazin-1-yl)-2-((tert-butoxycarbonyl)amino)propanoic acid (850 mg, 2.09 mmol) in CF3CH2OH (15 mL) was added Pd / C (200 mg, 10% purity) under N2. The suspension was degassed in vacuo and then purged with H2 several times. The mixture was stirred at 25 °C under H2 (15 psi) for 12 h. LCMS confirmed complete consumption of the starting material. The mixture was filtered, and the filter cake was washed with CF3CH2OH (50 mL). The filtrate was concentrated under reduced pressure to give the title compound (590 mg, crude) as a light brown solid. MS (M+H) + =274.1.

[0182] Step 7. Synthesis of 2-((tert-butoxycarbonyl)amino)-3-(4-(2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4-yl)piperazin-1-yl)propanoic acid (7) A mixture of 2-(2,6-dioxopiperidin-3-yl)-4-fluoroisoindoline-1,3-dione (600 mg, 2.17 mmol), 2-((tert-butoxycarbonyl)amino)-3-(piperazin-1-yl)propanoic acid (600.00 mg, 2.20 mmol), and DIPEA (890.40 mg, 6.89 mmol, 1.20 mL) in DMSO (10 mL) was stirred at 100° C. for 12 hours. LCMS confirmed complete consumption of 2-(2,6-dioxopiperidin-3-yl)-4-fluoroisoindoline-1,3-dione, with a peak corresponding to 74% of the desired mass. The mixture was adjusted to pH 7 by adding AcOH, and the resulting mixture was filtered. The filtrate was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 40 mm x 15 μm; mobile phase: [water (FA)-ACN]; B%: 10%-40%, 15 min), and the eluate was lyophilized to give the title compound (460 mg, 868.68 μmol, 39.99% yield) as an orange solid. MS (M+H) + =530.2.

[0183] Step 8. Synthesis of tert-butyl (1-(4-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamido)piperidin-1-yl)-3-(4-(2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4-yl)piperazin-1-yl)-1-oxopropan-2-yl)carbamate (9) A mixture of 2-((tert-butoxycarbonyl)amino)-3-(4-(2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4-yl)piperazin-1-yl)propanoic acid (180 mg, 339.92 μmol), HATU (181.70 mg, 477.86 μmol), and DIPEA (285.05 mg, 2.21 mmol, 384.16 μL) in DMF (5 mL) was stirred at 25° C. for 15 min, followed by (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo- 5,6,7,8-Tetrahydropteridin-2-yl)amino)-3-methoxy-N-(piperidin-4-yl)benzamide (200 mg, 367.59 μmol, HCl salt) was added, and the resulting mixture was stirred at 25 °C for 2 h. LCMS confirmed that 2-((tert-butoxycarbonyl)amino)-3-(4-(2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoindolin-4-yl)piperazin-1-yl)propanoic acid remained, with a peak of 67% of the desired mass detected. The mixture was diluted with HO (15 mL) and extracted with EtOAc (10 mL × 3). The combined organic phase was washed with brine (15 mL × 5), dried over NaSO, filtered, and concentrated under reduced pressure. The residue was purified by prep-TLC (SiO2, DCM:MeOH = 15:1, twice) to give the title compound (320 mg, 313.99 μmol, 85.42% yield) as a yellow solid. MS (M+H) + =1019.4.

[0184] Step 9. Synthesis of N-(1-(2-amino-3-(4-(2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4-yl)piperazin-1-yl)propanoyl)piperidin-4-yl)-4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamide (Compound 9) To a solution of tert-butyl (1-(4-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamido)piperidin-1-yl)-3-(4-(2-(2,6-dioxopiperidin-3-yl)-1,3-dioxoisoindolin-4-yl)piperazin-1-yl)-1-oxopropan-2-yl)carbamate (320 mg, 313.99 μmol) in DCM (5 mL) was added HCl / dioxane (4 M, 5 mL) and stirred at 25° C. for 1 h. LCMS confirmed complete consumption of the starting material, with a peak of 75% of the desired mass. The mixture was concentrated under reduced pressure. The residue was diluted with DMF (2.5 mL) and adjusted to pH >7 with DIPEA. The resulting mixture was purified by prep-HPLC (column: Waters xbridge 150*25 mm 10 μm; mobile phase: [water(NH4HCO3)-ACN]; B%: 35%-65%, 10 min), and the eluate was lyophilized to give the title compound (127.0 mg, 129.34 μmol, 41.19% yield, 93.6% purity) as a yellow solid. MS (M+H) + =919.5.

[0185] [ka]

[0186] Example 10 Synthesis of N-(1-(2-amino-3-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)propanoyl)piperidin-4-yl)-4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(trifluoromethoxy)benzamide (Compound 10)

[0187] [ka]

[0188] Step 1. Synthesis of tert-butyl (1-(4-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(trifluoromethoxy)benzamido)piperidin-1-yl)-3-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)-1-oxopropan-2-yl)carbamate (3) A solution of 2-((tert-butoxycarbonyl)amino)-3-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)propanoic acid (200 mg, 342.22 μmol, 78.8% purity) in DMF (6 mL) was diluted with EDCI (78.72 mg, 410.66 μmol) and HOBt (55.49 mg, 410.66 μmol), DIP EA (132.69 mg, 1.03 mmol, 178.82 μL) and (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(piperidin-4-yl)-3-(trifluoromethoxy)benzamide (204.67 mg, 342.22 μmol, HCl salt) were added. The mixture was stirred at 25 °C for 1 h. LCMS showed ~60% of the desired mass. The reaction mixture was diluted with water (30 mL) and extracted with EtOAc (20 mL × 3). The combined organic phase was washed with saturated brine (50 mL), dried over Na2SO4, filtered, and concentrated in vacuo. The residue was purified by flash silica gel chromatography (ISCO®; 12 g SepaFlash® silica flash column, eluent: 0-40% petroleum ether: EtOAc / EtOH (v / v = 5 / 1) gradient @ 80 mL / min) to afford the title compound as a yellow oil (180 mg, 169.23 μmol, 49.45% yield, 94.4% purity). MS (M+H) + =1004.5.

[0189] Step 2. Synthesis of N-(1-(2-amino-3-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)propanoyl)piperidin-4-yl)-4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(trifluoromethoxy)benzamide (Compound 10) To a solution of tert-butyl (1-(4-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(trifluoromethoxy)benzamido)piperidin-1-yl)-3-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)-1-oxopropan-2-yl)carbamate (180 mg, 179.26 μmol) in DCM (2 mL) at 0° C. was added TFA (3.08 g, 27.01 mmol, 2 mL). The mixture was stirred at 25° C. for 2 h. LCMS showed ∼72.7% of the desired mass peak (∼72.7%). The mixture was concentrated under reduced pressure to give the residue. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 40 mm x 15 μm; mobile phase: [water (TFA)-ACN]; B%: 15%-45%, 10 min) and then lyophilized to give the title compound (56 mg, 54.46 μmol, 30.38% yield, 99% purity, TFA salt) as a white solid. MS (M+H) + =904.4.

[0190] [ka]

[0191] Example 11 Synthesis of N-(1-(2-amino-3-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)propanoyl)piperidin-4-yl)-4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamide (Compound 11)

[0192] [ka]

[0193] Step 1. Synthesis of tert-butyl (1-(4-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamido)piperidin-1-yl)-3-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)-1-oxopropan-2-yl)carbamate (3) To a solution of 2-((tert-butoxycarbonyl)amino)-3-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)propanoic acid (200 mg, 342.22 μmol, 78.8% purity) in DMF (5 mL) was added EDCI (78.73 mg, 410.66 μmol), (R)-4-((8-cyclopentyl-7-ethyl- 5-Methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(piperidin-4-yl)benzamide (186.20 mg, 342.22 μmol, HCl salt), DIPEA (132.69 mg, 1.03 mmol, 178.83 μL), and HOBt (55.49 mg, 410.66 μmol) were added. The mixture was stirred at 25 °C for 2 hours. LCMS showed ~60% of the desired mass. The reaction mixture was diluted with water (30 mL) and extracted with EtOAc (20 mL x 3). The combined organic phase was washed with saturated brine (50 mL), dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (ISCO®; 12 g SepaFlash® silica flash column, eluent: 0-50% petroleum ether: EtOAc / EtOH (v / v = 5 / 1) gradient @ 80 mL / min) to afford the title compound (180 mg, 159.51 μmol, 46.61% yield, 84.2% purity) as a yellow solid. MS (M+H) + =950.4.

[0194] Step 2. Synthesis of N-(1-(2-amino-3-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)propanoyl)piperidin-4-yl)-4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamide (Compound 11) To a solution of tert-butyl (1-(4-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamido)piperidin-1-yl)-3-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)-1-oxopropan-2-yl)carbamate (180 mg, 189.45 μmol) in DCM (2 mL) at 0° C. was added TFA (3.08 g, 27.01 mmol, 2 mL). The mixture was stirred at 25° C. for 1 h. LCMS showed ∼76% of the desired mass peak (∼76%). The reaction mixture was concentrated under reduced pressure to give the residue. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150x40mmx15μm; mobile phase: [water (TFA)-ACN]; B%: 10%-40%, 10 min) and prep-HPLC (column: Waters Xbridge 150x25mmx5μm; mobile phase: [water (NH4HCO3)-ACN]; B%: 36%-66%, 10 min), followed by lyophilization to give the title compound (61.4 mg, 71.08 μmol, 37.52% yield, 98.4% purity) as a white solid. MS (M+H) + =850.2.

[0195] [ka]

[0196] Example 12 Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((2-(2,6-dioxopiperidin-3-yl)-1-oxoisoindolin-4-yl)methyl)amino)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 12)

[0197] [ka]

[0198] Step 1. Synthesis of benzyl ((1r,4r)-4-(4-oxopiperidin-1-yl)cyclohexyl)carbamate (3) To a solution of benzyl ((1r,4r)-4-aminocyclohexyl)carbamate (200 mg, 702.29 μmol, HCl) in MeOH (2 mL) were added 1,5-dichloropentan-3-one (108.87 mg, 702.29 μmol) and NaHCO (294.99 mg, 3.51 mmol, 136.63 μL), and the mixture was stirred at 75 °C for 16 h. LCMS showed a peak corresponding to the desired mass overlapping with other peaks. A new spot was detected by TLC (DCM:MeOH = 10:1). The mixture was diluted with H O (10 mL) and extracted with EtOAc (10 mL × 3). The combined organic phase was washed with brine (20 mL × 2), dried over Na SO , and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (Biotage; 10 g SepaFlash® silica flash column, eluent: 50-100% EtOAc / petroleum ether to 10% MeOH / EtOAc gradient @ 100 mL / min) to afford the title compound (140 mg, 423.70 μmol, 60.33% yield) as a yellow solid. MS (M+H) + =331.1.

[0199] Step 2. Synthesis of benzyl ((1r,4r)-4-(4-(((2-(2,6-dioxopiperidin-3-yl)-1-oxoisoindolin-4-yl)methyl)amino)piperidin-1-yl)cyclohexyl)carbamate (5) A mixture of benzyl ((1r,4r)-4-(4-oxopiperidin-1-yl)cyclohexyl)carbamate (140 mg, 423.70 μmol), 3-(4-(aminomethyl)-1-oxoisoindolin-2-yl)piperidine-2,6-dione (115.79 mg, 423.70 μmol), and TEA (128.62 mg, 1.27 mmol, 176.92 μL) in DCM (2 mL) was stirred at 20 °C for 0.5 h. NaBH(OAc) (269.40 mg, 1.27 mmol) was then added, and the mixture was stirred at 20 °C for 16 h. LCMS showed the main peak of the desired mass. The mixture was filtered through a pad of Celite. The filtrate was quenched with NaHCO (5 mL) and extracted with EtOAc (10 mL × 5). The combined organic phase was dried over Na2SO4, filtered, and the filtrate was concentrated under reduced pressure to give the title compound (100 mg, crude) as a yellow solid. MS (M+H) + =588.3.

[0200] Step 3. Synthesis of 3-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)amino)methyl)-1-oxoisoindolin-2-yl)piperidine-2,6-dione (6) A mixture of benzyl ((1r,4r)-4-(4-(((2-(2,6-dioxopiperidin-3-yl)-1-oxoisoindolin-4-yl)methyl)amino)piperidin-1-yl)cyclohexyl)carbamate (100 mg, 170.15 μmol) in TFA (1 mL) was stirred at 60° C. for 4 hours. LCMS showed a peak corresponding to the desired mass. The mixture was concentrated under reduced pressure to give the title compound (90 mg, 158.56 μmol, 93.19% yield, TFA) as a brown oil. MS (M+H) + =454.2.

[0201] Step 4. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(((2-(2,6-dioxopiperidin-3-yl)-1-oxoisoindolin-4-yl)methyl)amino)piperidin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 12) To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (67.47 mg, 158.56 μmol) in DMF (1 mL) was added HATU (72.35 mg, 190.28 μmol) and DIPEA (122.96 mg, 951.38 μmol, 165.71 μL), and the mixture was stirred at 20° C. for 0.5 h. 3-(4-(((1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)amino)methyl)-1-oxoisoindolin-2-yl)piperidine-2,6-dione (90 mg, 158.56 μmol, TFA) was added, and the mixture was stirred at 20° C. for 16 h. LCMS revealed a peak of the desired mass (70%) overlapping with other peaks. The mixture was diluted with water and HO (5 mL) and extracted with EtOAc (10 mL × 3). The combined organic phase was washed with brine (20 mL × 2), dried over NaSO, and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by reverse-phase HPLC (column: Waters Xbridge 150*25 mm*5 μm; mobile phase: [water(NH4HCO3)-ACN]; B%: 37%-67%, 9 min) and lyophilized to give the title compound (18.1 mg, 19.13 μmol, 12.06% yield, 91% purity) as a white solid. MS (M+H) + =861.4.

[0202] [ka]

[0203] Example 13 Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1-((1-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperidin-4-yl)methyl)piperidin-4-yl)methyl)-3-methoxybenzamide (Compound 13)

[0204] [ka]

[0205] Step 1. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1-((1-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperidin-4-yl)methyl)piperidin-4-yl)methyl)-3-methoxybenzamide (Compound 13) To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (61.29 mg, 144.05 μmol) in DMF (1 mL) was added HATU (65.73 mg, 172.87 μmol) and DIPEA (18.62 mg, 144.05 μmol, 25.09 μL) at 20° C. After stirring for 10 min, a solution of 3-((4-(4-((4-(aminomethyl)piperidin-1-yl)methyl)piperidin-1-yl)phenyl)amino)piperidine-2,6-dione (114 mg, 216.08 μmol, TFA) in DMF (1 mL) and DIPEA (290.82 mg, 2.25 mmol, 391.94 μL) was added at 20 °C, followed by stirring at 20 °C for 16 h. LCMS confirmed complete consumption of the starting material, and a peak corresponding to 50% of the desired mass was detected. The mixture was diluted with HO (20 mL) and extracted with EtOAc (10 mL × 3). The combined organic phase was washed with brine (10 mL × 3), dried over NaSO, filtered, and concentrated under reduced pressure to give a residue. The residue was purified by prep-TLC (SiO, DCM:MeOH = 5:1). The product was dissolved in a mixture (20 mL, ACN:H2O = 1:3) and lyophilized to give the title compound (21 mg, 24.04 μmol, 16.45% yield, 94% purity) as an off-white solid. MS (M+H) + =821.2

[0206] [ka]

[0207] Example 14 Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(1-(3-(4-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperazin-1-yl)propanoyl)piperidin-4-yl)-3-(trifluoromethoxy)benzamide (Compound 14)

[0208] [ka]

[0209] Step 1. Synthesis of methyl (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(trifluoromethoxy)benzoate (3) To a solution of (R)-2-chloro-8-cyclopentyl-7-ethyl-5-methyl-7,8-dihydropteridin-6(5H)-one (398.87 mg, 1.70 mmol) in DMF (8 mL) were added Pd(OAc) (38.08 mg, 169.62 μmol), BINAP (211.23 mg, 339.24 μmol), and CsCO (1.11 g, 3.39 mmol). The reaction mixture was stirred at 80 °C under N for 12 h. LCMS showed the desired mass peak (57%). The mixture was adjusted to pH 7 with 1 N HCl solution and extracted with EtOAc (50 mL x 2). The combined organic phase was dried over NaSO and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (ISCO®; 40 g SepaFlash® silica flash column, eluent: 0-30% EtOAc / petroleum ether gradient @ 60 mL / min) to afford the title compound (330 mg, 668.72 μmol, 39.43% yield) as a yellow oil. MS (M+H) + =494.3.

[0210] Step 2. Synthesis of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(trifluoromethoxy)benzoic acid (4) To a solution of methyl (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(trifluoromethoxy)benzoate (330 mg, 668.72 μmol) in THF (1.5 mL) and MeOH (1.5 mL) was added a solution of NaOH (40.12 mg, 1.00 mmol) in HO (0.5 mL) and stirred at 15° C. for 16 h. LCMS showed 12% of methyl (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(trifluoromethoxy)benzoate remaining, and a peak with the desired mass (59%) was detected. The mixture was adjusted to pH 6 with HCl solution and concentrated under reduced pressure to give the title compound (320 mg, 667.43 μmol) as a white solid, which was used in the next step without further purification. MS (M+H) + =480.2

[0211] Step 3. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(1-(3-(4-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperazin-1-yl)propanoyl)piperidin-4-yl)-3-(trifluoromethoxy)benzamide (Compound 14) To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-(trifluoromethoxy)benzoic acid (97 mg, 168.75 μmol) in DMF (0.2 mL) was added HATU (133.22 mg, 350.36 μmol) and DIPEA (150.94 mg, 1.17 mmol, 203.42 μL). The mixture was stirred at 25° C. for 0.5 h. Then, 3-((4-(4-(3-(4-aminopiperidin-1-yl)-3-oxopropyl)piperazin-1-yl)phenyl)amino)piperidine-2,6-dione (130 mg, 233.57 μmol, TFA) was added to the mixture, which was then stirred at 25° C. for 16 h. LCMS confirmed complete consumption of 3-((4-(4-(3-(4-aminopiperidin-1-yl)-3-oxopropyl)piperazin-1-yl)phenyl)amino)piperidine-2,6-dione, and a peak of the desired mass was detected. The reaction mixture was diluted with HO (10 mL) at 25 °C and extracted with EtOAc (80 mL). The combined organic phase was washed with brine (10 mL), dried over NaSO, filtered, and concentrated in vacuo. The residue was purified by flash silica gel chromatography (ISCO®; 20 g SepaFlash® silica flash column, eluent: 0-15% MeOH / EtOAc @ 50 mL / min) and then repurified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x 10 μm; mobile phase: [water (TFA)-ACN]; gradient: 23%-53% B over 9 min). The eluate was lyophilized to afford the title compound (53.8 mg, 45.62 μmol, 19.53% yield, 96% purity, 2% TFA) as a purple solid. MS (M+H) + =904.4.

[0212] [ka]

[0213] Example 15 Synthesis of 3-(4-(4-(2-amino-3-(4-(((5-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxyphenyl)-1,3,4-oxadiazol-2-yl)methyl)amino)piperidin-1-yl)-3-oxopropyl)piperazin-1-yl)phenyl)piperidine-2,6-dione (Compound 15)

[0214] [ka]

[0215] Step 1. Synthesis of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (3) To a solution of (R)-2-chloro-8-cyclopentyl-7-ethyl-5-methyl-7,8-dihydropteridin-6(5H)-one (8 g, 27.14 mmol) in EtOH (100 mL) was added 4-amino-3-methoxybenzoic acid (4.4 g, 26.32 mmol) and a solution of HCl (12 M, 4.6 mL) in HO (400 mL) at 20 °C. The mixture was stirred at 100 °C for 16 hours. LCMS showed the desired mass peak (50%). After stirring at 20 °C for 1 hour, the mixture was filtered, and the filter cake was dried under reduced pressure to give the title compound (6 g, crude) in a pale yellow color. MS (M+H) + =426.2

[0216] Step 2. Synthesis of tert-butyl (R)-2-(4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoyl)hydrazine-1-carboxylate (4) To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (5 g, 11.75 mmol) in DMF (50 mL) was added HATU (6.75 g, 17.75 mmol), DIPEA (5.94 g, 45.93 mmol, 8 mL), and tert-butyl hydrazine carboxylate (1.8 g, 13.62 mmol) at 20 °C. The mixture was stirred at 20 °C under N for 16 h. LCMS showed the main peak of the desired mass. The mixture was diluted with H2O (100 mL) and extracted with EtOAc (150 mL x 2). The combined organic phase was washed with brine (200 mL x 3), dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue was triturated with a solvent (EtOAc:MTBE=1:2; 90 mL) at 20° C. for 1 hour. The mixture was filtered, and the filter cake was dried to give the title compound (5.2 g, 9.64 mmol, 82.00% yield) as a pale yellow solid. MS (M+H) + =540.3

[0217] Step 3. Synthesis of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzohydrazide (5) To a solution of tert-butyl (R)-2-(4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoyl)hydrazine-1-carboxylate in DCM (15 mL) at 20°C, TFA (12.28 g, 107.70 mmol, 8 mL) was added, and the mixture was stirred at 20°C for 2 hours. LCMS showed the main peak corresponding to the desired mass. The mixture was concentrated under reduced pressure to give the title compound (2 g, crude, TFA) as a pale yellow oil. MS (M+H) + =440.3

[0218] Step 4. Synthesis of (R)-N'-(2-chloroacetyl)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzohydrazide (6) To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzohydrazide (2 g, crude, TFA) in DCM (40 mL) was added DIPEA (3.71 g, 28.71 mmol, 5 mL) and 2-chloroacetyl chloride (397.04 mg, 3.52 mmol, 280 μL) at 0 °C. The mixture was stirred at 20 °C under N for 1 h. LCMS showed the desired mass peak (56%). The reaction mixture was diluted with H2O (20 mL) and extracted with DCM (50 mL × 2). The combined organic phase was washed with brine (60 mL × 2), dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (80 g SepaFlash® silica flash column, eluent: 75-100% EtOAc / petroleum ether gradient @ 100 mL / min) to afford the title compound (1.5 g, 2.91 mmol, 80.46% yield) as a pale yellow oil. MS (M+H) + =516.2

[0219] Step 5. Synthesis of (R)-2-((4-(5-(chloromethyl)-1,3,4-oxadiazol-2-yl)-2-methoxyphenyl)amino)-8-cyclopentyl-7-ethyl-5-methyl-7,8-dihydropteridin-6(5H)-one (7) A mixture of (R)-N'-(2-chloroacetyl)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzohydrazide (800 mg, 1.55 mmol) in POCl3 (13.16 g, 85.83 mmol, 8.00 mL) was stirred at 80 °C under N2 for 32 h. LCMS showed (R)-N'-(2-chloroacetyl)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzohydrazide remaining (7%) and a peak for the desired mass (65%). The mixture was concentrated under reduced pressure to remove POCl3. The product was diluted with DCM (30 mL), and the combined organic phase was washed with NaHCO3 (30 mL x 2) solution, dried over Na2SO4, filtered, and concentrated under reduced pressure to give the title compound (770 mg, crude) as a yellow solid. MS (M+H) + =498.1

[0220] Step 6. Synthesis of tert-butyl (R)-4-(((5-(4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxyphenyl)-1,3,4-oxadiazol-2-yl)methyl)amino)piperidine-1-carboxylate (8) To a solution of (R)-2-((4-(5-(chloromethyl)-1,3,4-oxadiazol-2-yl)-2-methoxyphenyl)amino)-8-cyclopentyl-7-ethyl-5-methyl-7,8-dihydropteridin-6(5H)-one (200 mg, 401.63 μmol) in DMF (3 mL) was added tert-butyl 4-aminopiperidine-1-carboxylate (90 mg, 449.38 μmol), DIPEA (222.59 mg, 1.72 mmol, 299.99 μL), and KI (60.00 mg, 361.45 μmol) at 20 °C under N. The mixture was stirred at 20 °C under N for 16 h. A peak corresponding to the desired mass was detected by LCMS. After diluting the reaction mixture with HO (10 mL), the mixture was extracted with EtOAc (25 mL × 2). The combined organic phase was washed with brine (20 mL x 3), dried over NaSO, filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (10 g SepaFlash® silica flash column, eluent: 0-10% MeOH:EtOAc gradient, 100 mL / min) to afford the title compound (300 mg, crude) as a pale yellow solid. MS (M+H) + =662.4

[0221] Step 7. Synthesis of (R)-8-cyclopentyl-7-ethyl-2-((2-methoxy-4-(5-((piperidin-4-ylamino)methyl)-1,3,4-oxadiazol-2-yl)phenyl)amino)-5-methyl-7,8-dihydropteridin-6(5H)-one (9) To a solution of tert-butyl (R)-4-(((5-(4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxyphenyl)-1,3,4-oxadiazol-2-yl)methyl)amino)piperidine-1-carboxylate (0.3 g, 453.31 μmol) in dioxane (4 mL) was added HCl / dioxane (4 M, 4 mL) at 20° C. The mixture was stirred at 20° C. for 2 hours. LCMS showed a peak corresponding to the desired mass. The mixture was concentrated under reduced pressure to give the title compound (270 mg, crude, HCl) as a pale yellow solid. MS (M+H)+ =562.3

[0222] Step 8. Synthesis of tert-butyl (1-(4-(((5-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxyphenyl)-1,3,4-oxadiazol-2-yl)methyl)amino)piperidin-1-yl)-3-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)-1-oxopropan-2-yl)carbamate (11) A solution of 2-((tert-butoxycarbonyl)amino)-3-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)propanoic acid (120 mg, 260.57 μmol) in DMF (2 mL) was added at 20 °C with EDCI (100.00 mg, 521.65 μmol), HOBt (40.00 mg, 296.03 μmol), DIPEA (296 To the resulting mixture were added (R)-8-cyclopentyl-7-ethyl-2-((2-methoxy-4-(5-((piperidin-4-ylamino)methyl)-1,3,4-oxadiazol-2-yl)phenyl)amino)-5-methyl-7,8-dihydropteridin-6(5H)-one (200.00 mg, crude, HCl). The mixture was stirred at 20 °C under N for 16 h. LCMS showed the desired mass peak (58%). The mixture was diluted with water (8 mL) and extracted with EtOAc (15 mL × 2). The combined organic phase was washed with brine (10 mL × 3), dried over Na SO , filtered, and concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150x25mmx10um; mobile phase: [water (TFA)-ACN]; gradient: 20%-50% B over 10 min; column temperature: 30°C) and re-purified by prep-HPLC (column: Waters Xbridge C18 150x50mmx10um; mobile phase: [water (NH4HCO3)-ACN]; gradient: 35%-65% B over 10 min; column temperature: 30°C) to give the title compound (210 mg, 209.13 μmol, 80.26% yield) as a pale yellow solid. MS (M+H) + =1004.7

[0223] Step 9. Synthesis of 3-(4-(4-(2-amino-3-(4-(((5-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxyphenyl)-1,3,4-oxadiazol-2-yl)methyl)amino)piperidin-1-yl)-3-oxopropyl)piperazin-1-yl)phenyl)piperidine-2,6-dione (Compound 15) To a solution of tert-butyl (1-(4-(((5-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxyphenyl)-1,3,4-oxadiazol-2-yl)methyl)amino)piperidin-1-yl)-3-(4-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperazin-1-yl)-1-oxopropan-2-yl)carbamate (170 mg, 169.29 μmol) in DCM (5 mL) was added TFA (6.14 g, 53.85 mmol, 4 mL) at 20° C. and stirred at 20° C. for 2 h. A peak of the desired mass was detected by LCMS. The mixture was concentrated under reduced pressure. The residue was freeze-dried to give the title compound (132.9 mg, crude, 3 TFA) as a pale yellow solid. MS (M+H) + =904.6

[0224] [ka]

[0225] Example 16 Synthesis of 3-(4-(((1-((1r,4r)-4-(((5-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxyphenyl)-1,3,4-oxadiazol-2-yl)methyl)amino)cyclohexyl)piperidin-4-yl)amino)methyl)phenyl)piperidine-2,6-dione (Compound 16)

[0226] [ka]

[0227] Step 1. Synthesis of benzyl (1-((1r,4r)-4-((tert-butoxycarbonyl)amino)cyclohexyl)piperidin-4-yl)(4-(2,6-dioxopiperidin-3-yl)benzyl)carbamate (2) To a solution of tert-butyl ((1r,4r)-4-(4-((4-(2,6-dioxopiperidin-3-yl)benzyl)amino)piperidin-1-yl)cyclohexyl)carbamate (500 mg, 1.00 mmol) in THF (5 mL) and water (5 mL) was added TEA (304.39 mg, 3.01 mmol, 418.69 μL). The mixture was cooled to 0 °C. CbzCl (342.10 mg, 2.01 mmol, 286.28 μL) was then slowly added to the mixture and stirred at 25 °C for 16 h. LCMS showed the desired mass peak (~25%). The mixture was diluted with water (20 mL) and extracted with EtOAc (30 mL × 3). The combined organic phase was washed with water (30 mL), dried over Na2SO4, and filtered. The filtrate was concentrated under reduced pressure to give the residue, which was purified by flash silica gel chromatography (ISCO®; 20 g SepaFlash® silica flash column, eluent: 30-40% MeOH / EtOAc gradient @ 80 mL / min) to give the title compound (410 mg, 647.93 μmol, 64.62% yield) as a yellow oil. MS (M+H) + =633.4.

[0228] Step 2. Synthesis of benzyl (1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)(4-(2,6-dioxopiperidin-3-yl)benzyl)carbamate (3) To a solution of benzyl (1-((1r,4r)-4-((tert-butoxycarbonyl)amino)cyclohexyl)piperidin-4-yl)(4-(2,6-dioxopiperidin-3-yl)benzyl)carbamate (620 mg, 979.79 μmol) in dioxane (6 mL) was added HCl / dioxane (4 M, 6 mL). The mixture was stirred at 25° C. for 2 hours. LCMS confirmed complete consumption of benzyl (1-((1r,4r)-4-((tert-butoxycarbonyl)amino)cyclohexyl)piperidin-4-yl)(4-(2,6-dioxopiperidin-3-yl)benzyl)carbamate, and a peak corresponding to the desired mass was detected. The mixture was concentrated under reduced pressure to give the title compound (600 mg, crude, HCl salt) as a yellow solid. MS (M+H) + =533.4.

[0229] Step 3. Synthesis of benzyl (1-((1r,4r)-4-(((5-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxyphenyl)-1,3,4-oxadiazol-2-yl)methyl)amino)cyclohexyl)piperidin-4-yl)(4-(2,6-dioxopiperidin-3-yl)benzyl)carbamate (5) To a solution of benzyl (1-((1r,4r)-4-aminocyclohexyl)piperidin-4-yl)(4-(2,6-dioxopiperidin-3-yl)benzyl)carbamate (300 mg, 527.12 μmol, HCl salt) and (R)-2-((4-(5-(chloromethyl)-1,3,4-oxadiazol-2-yl)-2-methoxyphenyl)amino)-8-cyclopentyl-7-ethyl-5-methyl-7,8-dihydropteridin-6(5H)-one (262.49 mg, 527.12 μmol) in DMF (5 mL) was added KI (8.75 mg, 52.71 μmol) and DIPEA (204.37 mg, 1.58 mmol, 275.44 μL). The mixture was stirred at 40° C. for 20 h. LCMS showed a peak of the desired mass (~54%). The residue was diluted with water (20 mL) and extracted with EtOAc (20 mL x 3). The combined organic phase was washed with brine (20 mL x 3), dried over Na2SO4, and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by prep-TLC (SiO2, EtOAc:MeOH = 2:1) to give the title compound (125 mg, 125.73 μmol, 23.85% yield) as a yellow solid. MS (M+H) + =994.6.

[0230] Step 4. Synthesis of 3-(4-(((1-((1r,4r)-4-(((5-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxyphenyl)-1,3,4-oxadiazol-2-yl)methyl)amino)cyclohexyl)piperidin-4-yl)amino)methyl)phenyl)piperidine-2,6-dione (Compound 16) To benzyl (1-((1r,4r)-4-(((5-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxyphenyl)-1,3,4-oxadiazol-2-yl)methyl)amino)cyclohexyl)piperidin-4-yl)(4-(2,6-dioxopiperidin-3-yl)benzyl)carbamate (125 mg, 125.73 μmol) was added TFA (4.61 g, 40.39 mmol, 3 mL). The mixture was stirred at 60° C. for 16 hours. A peak of the desired mass was detected by LCMS. The mixture was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 40 mm x 15 μm; mobile phase: [water (TFA)-ACN]; gradient: 10%-40% B over 10 min), and the eluate was lyophilized to give the title compound as a white solid (113.3 mg, 88.31 μmol, 70.24% yield, 93.7% purity, 3TFA salt). MS (M+H) + =860.5.

[0231] [ka]

[0232] Example 17 Synthesis of 3-(4-(4-((((1r,4r)-4-(((5-(4-((((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxyphenyl)-1,3,4-oxadiazol-2-yl)methyl)amino)cyclohexyl)amino)methyl)piperidin-1-yl)-3-fluorophenyl)piperidine-2,6-dione (Compound 17)

[0233] [ka]

[0234] Step 1. Synthesis of tert-butyl ((1r,4r)-4-(((5-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxyphenyl)-1,3,4-oxadiazol-2-yl)methyl)amino)cyclohexyl)carbamate (3) To a solution of (R)-2-((4-(5-(chloromethyl)-1,3,4-oxadiazol-2-yl)-2-methoxyphenyl)amino)-8-cyclopentyl-7-ethyl-5-methyl-7,8-dihydropteridin-6(5H)-one (200 mg, 401.63 μmol) in DMF (4 mL) was added tert-butyl ((1r,4r)-4-aminocyclohexyl)carbamate (120 mg, 478.54 μmol, HCl), DIPEA (267.12 mg, 2.07 mmol, 360.00 μL), and KI (60.00 mg, 361.44 μmol) at 20 °C under N2 for 20 h. The desired mass peak (77%) was detected by LCMS. The reaction mixture was diluted with H2O (10 mL), and the mixture was extracted with EtOAc (30 mL x 2). The combined organic phases were washed with brine (20 mL x 3), dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (Biotage; 10 g SepaFlash® silica flash column, eluent 0-10% MeOH:EtOAc gradient, 100 mL / min) to afford the title compound (300 mg, crude) as a pale yellow solid. MS (M+H) + =676.4

[0235] Step 2. Synthesis of (R)-2-((4-(5-((((1r,4r)-4-aminocyclohexyl)amino)methyl)-1,3,4-oxadiazol-2-yl)-2-methoxyphenyl)amino)-8-cyclopentyl-7-ethyl-5-methyl-7,8-dihydropteridin-6(5H)-one (4) To a solution of tert-butyl ((1r,4r)-4-(((5-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxyphenyl)-1,3,4-oxadiazol-2-yl)methyl)amino)cyclohexyl)carbamate (300 mg, crude) in dioxane (5 mL) was added HCl / dioxane (4 M, 8 mL) at 20° C. and stirred at 20° C. for 2 hours. LCMS showed a peak corresponding to the desired mass. The reaction mixture was concentrated under reduced pressure to give the title compound (270 mg, crude, HCl) as a pale yellow solid. MS (M+H) + =576.3

[0236] Step 3. Synthesis of 3-(4-(4-((((1r,4r)-4-(((5-(4-((((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxyphenyl)-1,3,4-oxadiazol-2-yl)methyl)amino)cyclohexyl)amino)methyl)piperidin-1-yl)-3-fluorophenyl)piperidine-2,6-dione (Compound 17) To a solution of 1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperidine-4-carbaldehyde (120 mg, 376.95 μmol) in DCM (4 mL) at 20° C. was added (R)-2-((4-(5-((((1r,4r)-4-aminocyclohexyl)amino)methyl)-1,3,4-oxadiazol-2-yl)-2-methoxyphenyl)amino)-8-cyclopentyl-7-ethyl-5-methyl-7,8-dihydropteridin-6(5H)-one (210.00 mg, 343.05 μmol, HCl) and TEA (228.86 mg, 2.26 mmol, 314.80 μL), followed by stirring at 20° C. for 1 h. After that, NaBH(OAc)3 (300.00 mg, 1.42 mmol) was added to the mixture, and the resulting mixture was stirred at 20 °C for 15 h. LCMS showed the desired mass peak (43%). The reaction mixture was adjusted to pH 9-10 with NaHCO3 (sat. aq., 4 mL) at 0 °C, extracted with DCM (15 mL × 2). The combined organic phase was washed with brine (20 mL × 2), dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 × 25 mm × 10 μm; mobile phase: [water (TFA)-ACN]; gradient: 16%-46% B over 10 min; column temperature: 30 °C). The eluate was lyophilized to give the title compound (123.7 mg, 99.25 μmol, 26.33% yield, 97.9% purity, 3TFA) as a pale yellow solid. MS (M+H) + =878.6

[0237] [ka]

[0238] Example 18 Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(((1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperidin-4-yl)methyl)amino)cyclohexyl)-3-methoxybenzamide (Compound 18)

[0239] [ka]

[0240] Step 1. Synthesis of 1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperidine-4-carbaldehyde (2) To a solution of 3-(3-fluoro-4-(4-(hydroxymethyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (2 g, 6.24 mmol) in DCM (50 mL) was added DMP (3.97 g, 9.36 mmol), and the mixture was stirred at 20° C. for 2 h. TLC (petroleum ether / EtOAc = 1 / 1) confirmed complete consumption of 3-(3-fluoro-4-(4-(hydroxymethyl)piperidin-1-yl)phenyl)piperidine-2,6-dione and the formation of a new spot. The mixture was filtered, and the filtrate was concentrated under reduced pressure to give the title compound (2 g, crude) as a yellow oil. MS (M+H) + =319.4

[0241] Step 2. Synthesis of benzyl ((1r,4r)-4-(((1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperidin-4-yl)methyl)amino)cyclohexyl)carbamate (4) To a solution of 1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperidine-4-carbaldehyde (2 g, 6.28 mmol) and benzyl ((1r,4r)-4-aminocyclohexyl)carbamate (1.56 g, 6.28 mmol) in DCM (20 mL) was added AcOH (377.28 mg, 6.28 mmol, 359.66 μL), and the mixture was stirred at 20 °C for 1 h. NaBH(OAc) (1.60 g, 7.54 mmol) was then added, and the resulting mixture was stirred at 20 °C for 12 h. LCMS showed the desired mass peak (43%). The mixture was diluted with water (100 mL) and extracted with DCM (50 mL x 3). The combined organic phase was washed with saturated brine (200 mL), dried over anhydrous NaSO, filtered, and concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 40 mm x 15 μm; mobile phase: [water (TFA)-ACN]; gradient: 15%-45% B over 10 min) to give the title compound (0.9 g, 1.57 mmol, 24.97% yield, 96% purity) as a yellow oil. MS (M+H) + =551.4

[0242] Step 3. Synthesis of 3-(4-(4-((((1r,4r)-4-aminocyclohexyl)amino)methyl)piperidin-1-yl)-3-fluorophenyl)piperidine-2,6-dione (5) A mixture of benzyl ((1r,4r)-4-(((1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperidin-4-yl)methyl)amino)cyclohexyl)carbamate (450 mg, 817.20 μmol) in TFA (7.68 g, 67.31 mmol, 5 mL) was stirred at 40° C. for 3 hours. LCMS showed the desired peak (79%). The mixture was concentrated under reduced pressure to give the title compound (0.4 g, 753.93 μmol, 92.26% yield, TFA) as a yellow oil. MS (M+H) + =417.3

[0243] Step 4. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(((1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperidin-4-yl)methyl)amino)cyclohexyl)-3-methoxybenzamide (Compound 18) To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (160.39 mg, 376.96 μmol) in DMF (5 mL) was added HATU (172.00 mg, 452.36 μmol) and DIPEA (194.88 mg, 1.51 mmol, 262.64 μL). After stirring at 20° C. for 1 h, 3-(4-(4-((((1r,4r)-4-aminocyclohexyl)amino)methyl)piperidin-1-yl)-3-fluorophenyl)piperidine-2,6-dione (0.2 g, 376.96 μmol, TFA) was added and the mixture was stirred at 20° C. for 12 h. The desired mass peak (60%) was detected by LCMS. The reaction mixture was diluted with water (50 mL) and extracted with EtOAc (30 mL x 3). The combined organic phase was washed with saturated brine (100 mL), dried over anhydrous Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex luna C18 150 x 40 mm x 15 μm; mobile phase: [water (TFA)-ACN]; gradient: 15%-45% B over 10 min). The eluate was adjusted to pH 9 with solid K2CO3, and the resulting mixture was extracted with EtOAc (30 mL x 3). The combined organic phase was washed with saturated brine (100 mL), dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue was lyophilized to give the title compound (121.3 mg, 139.85 μmol, 37.10% yield, 95% purity) as a white solid. MS(M+H) + =824.5.

[0244] [ka]

[0245] Example 19 Synthesis of N-(4-(1-amino-2-(4-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamide (Compound 19)

[0246] [ka]

[0247] Step 1. Synthesis of benzyl (1-(1-((tert-butoxycarbonyl)amino)piperidin-4-yl)-2-(4-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperazin-1-yl)ethyl)carbamate (2) To a solution of benzyl (1-(1-aminopiperidin-4-yl)-2-(4-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperazin-1-yl)ethyl)carbamate (170 mg, 300.00 μmol) in THF (3 mL) was added TEA (212.50 mg, 2.10 mmol, 292.29 μL) and BocO (196.42 mg, 900.00 μmol, 206.76 μL), and the mixture was stirred at 25 °C for 12 h. LCMS showed a peak corresponding to 38% of the desired mass. The mixture was diluted with brine (10 mL) and extracted with EtOAc (10 mL x 3). The combined organic phase was diluted with water (10 mL), dried over NaSO, and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by prep-TLC (DCM:MeOH=20:1) to give the title compound (40 mg, 59.99 μmol, 20.00% yield) as a yellow solid. MS (M+H) + =667.4

[0248] Step 2. Synthesis of benzyl (1-(1-aminopiperidin-4-yl)-2-(4-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperazin-1-yl)ethyl)carbamate (3) To a solution of benzyl (1-(1-((tert-butoxycarbonyl)amino)piperidin-4-yl)-2-(4-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperazin-1-yl)ethyl)carbamate (40 mg, 59.99 μmol) in DCM (0.5 mL) was added TFA (122.80 mg, 1.08 mmol, 80 μL) and stirred at 25° C. for 1 h. LCMS showed a peak corresponding to 82% of the desired mass. The mixture was concentrated under reduced pressure to give the title compound (40 mg, crude, TFA) as a yellow oil. MS (M+H) + =567.4

[0249] Step 3. Synthesis of benzyl (1-(1-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamido)piperidin-4-yl)-2-(4-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperazin-1-yl)ethyl)carbamate (5) To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (30 mg, 70.51 μmol) and HATU (27 mg, 71.01 μmol) in DMF (1 mL) was added DIPEA (74.20 mg, 574.11 μmol, 0.1 mL), and the mixture was stirred at 25° C. for 15 min. Then, a solution of benzyl (1-(1-aminopiperidin-4-yl)-2-(4-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperazin-1-yl)ethyl)carbamate (40 mg, crude, TFA) was added at 0° C., and the mixture was stirred at 25° C. for 1 h. LCMS showed a peak corresponding to 36% of the desired mass. The mixture was diluted with water (10 mL) and extracted with EtOAc (10 mL x 3). The combined organic phase was washed with brine (10 mL), dried over Na2SO4, and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by prep-TLC (DCM:MeOH = 10:1) to give the title compound (40 mg, 40.24 μmol, 68.48% yield, 98% purity) as a yellow solid. MS (M+H) + =974.5

[0250] Step 4. Synthesis of N-(4-(1-amino-2-(4-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamide (Compound 19) A solution of benzyl (1-(1-(4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzamido)piperidin-4-yl)-2-(4-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperazin-1-yl)ethyl)carbamate (120 mg, 123.19 μmol) in TFA (7.68 g, 67.31 mmol, 5 mL) was stirred at 60° C. for 4.5 h. LCMS showed a small amount of starting material remaining, with the desired mass peak (52%) detected. The mixture was concentrated under reduced pressure and purified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x 10 μm; mobile phase: [water (TFA)-ACN]; gradient: 17%-47% B over 10 min). The eluate was lyophilized to give the title compound (37.3 mg, 30.92 μmol, 25.10% yield, 98% purity, 3% TFA) as a white solid. MS (M+H) + =840.5

[0251] [ka]

[0252] Example 20 Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(4-(2,6-dioxopiperidin-3-yl)phenethyl)piperazin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 20)

[0253] [ka]

[0254] Step 1. Synthesis of 2-(4-(2,6-bis(benzyloxy)pyridin-3-yl)phenyl)ethan-1-ol (3) A mixture of 2-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)ethan-1-ol (3 g, 12.09 mmol), 2,6-bis(benzyloxy)-3-bromopyridine (4.50 g, 12.15 mmol), CsCO (7.88 g, 24.18 mmol), and Pd(dppf)Cl (900.00 mg, 1.23 mmol) in dioxane (6 mL) and HO (1.2 mL) was degassed and purged under N. The mixture was stirred at 100 °C for 16 h. LCMS showed a main peak corresponding to the desired mass. The reaction mixture was filtered. The filtrate was diluted with HO (80 mL) and extracted with EtOAc (150 mL × 2). The combined organic phase was washed with brine (100 mL × 2), dried over NaSO, filtered, and concentrated under reduced pressure to give a residue, which was then purified by flash silica gel chromatography (Biotage; 40 g SepaFlash® silica flash column, eluent: 15–25% EtOAc:petroleum ether gradient, 100 mL / min) to give the title compound (4.9 g, 11.91 mmol, 98.49% yield) as a pale yellow oil. MS (M+H) + =412.2

[0255] Step 2. Synthesis of 3-(4-(2-hydroxyethyl)phenyl)piperidine-2,6-dione (4) To a solution of 2-(4-(2,6-bis(benzyloxy)pyridin-3-yl)phenyl)ethan-1-ol (1.9 g, 4.62 mmol) in CF3CH2OH (50 mL) was added Pd / C (4.91 g, 4.62 mmol, 10% purity) under N2. The suspension was degassed and purged with H2 three times. The mixture was then stirred at 20 °C under H2 (15 Psi) for 32 h. LCMS confirmed complete consumption of 2-(4-(2,6-bis(benzyloxy)pyridin-3-yl)phenyl)ethan-1-ol, and a peak corresponding to the desired mass was detected. The reaction mixture was filtered. The filtrate was concentrated under reduced pressure. The compound was triturated with MTBE (15 mL) at 20 °C for 1 h. The mixture was filtered. The filter cake was dried to give the title compound (800 mg, 3.43 mmol, 74.28% yield) as a pale yellow solid. MS(M+H)+ =234.1

[0256] Step 3. Synthesis of 2-(4-(2,6-dioxopiperidin-3-yl)phenyl)acetaldehyde (5) To a solution of 3-(4-(2-hydroxyethyl)phenyl)piperidine-2,6-dione (500 mg, 2.14 mmol) in DCM (10 mL) was added DMP (1.09 g, 2.57 mmol, 796.92 μL) at 25 °C. The mixture was stirred at 25 °C for 2 h. LCMS showed the main peak of the desired mass. The reaction mixture was diluted with H2O (10 mL) at 20 °C and extracted with DCM (30 mL x 2). The combined organic phase was washed with NaHCO3 (sat, aq, 30 mL x 3), dried over Na2SO4, filtered, and concentrated under reduced pressure to give the title compound (490 mg, crude) as a pale yellow oil. MS (M+H) + =232.1

[0257] Step 4. Synthesis of tert-butyl ((1r,4r)-4-(4-(4-(2,6-dioxopiperidin-3-yl)phenethyl)piperazin-1-yl)cyclohexyl)carbamate (7) To a solution of 2-(4-(2,6-dioxopiperidin-3-yl)phenyl)acetaldehyde (490 mg, 2.12 mmol) in DCM (20 mL) was added tert-butyl ((1r,4r)-4-(piperazin-1-yl)cyclohexyl)carbamate (544.44 mg, 1.92 mmol) and TEA (1.29 g, 12.71 mmol, 1.77 mL) at 20 °C and stirred at 20 °C for 1 h. NaBH(OAc) (1.35 g, 6.36 mmol) was then added, and the resulting mixture was stirred at 20 °C for 15 h. LCMS showed the desired mass peak (28%). The pH of the reaction mixture was adjusted to 9-10 with NaHCO (sat. aq. 20 mL) at 0 °C and extracted with DCM (30 ml × 2). The combined organic phase was washed with brine (30 mL × 2), dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue was diluted with DMF (6 mL) and filtered. The filter cake was concentrated under reduced pressure to give 350 mg of product. The filtrate was purified by prep-HPLC (column: Phenomenex Luna C18 150 × 40 mm × 15 μm; mobile phase: [water (TFA)-ACN]; gradient: 5%-35% B over 10 min, column temperature: 30 °C). The eluate was lyophilized to give the title compound (440 mg, 882.37 μmol, 41.64% yield) as a pale yellow solid. MS (M+H) + =499.3

[0258] [ka]

[0259] Step 5. Synthesis of 3-(4-(2-(4-((1r,4r)-4-aminocyclohexyl)piperazin-1-yl)ethyl)phenyl)piperidine-2,6-dione (8) To a solution of tert-butyl ((1r,4r)-4-(4-(4-(2,6-dioxopiperidin-3-yl)phenethyl)piperazin-1-yl)cyclohexyl)carbamate (300 mg, 601.62 μmol) in dioxane (2 mL) was added HCl / dioxane (2 M, 12 mL) at 20° C., followed by stirring at 20° C. for 2 hours. LCMS showed the main peak corresponding to the desired mass. The mixture was concentrated under reduced pressure to give the title compound (260 mg, crude, HCl salt) as a white solid. MS (M+H) + =399.3

[0260] Step 6. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(4-(4-(2,6-dioxopiperidin-3-yl)phenethyl)piperazin-1-yl)cyclohexyl)-3-methoxybenzamide (Compound 20) To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (260 mg, 611.07 μmol) in DMF (5 mL) was added EDCI (200 mg, 1.04 mmol), HOBt (120 mg, 888.08 μmol), DIPEA (519.40 mg, 4.02 mmol, 700 μL), and 3-(4-(2-(4-((1r,4r)-4-aminocyclohexyl)piperazin-1-yl)ethyl)phenyl)piperidine-2,6-dione (260 mg, 597.70 μmol, HCl) at 20° C. under N for 16 h. The desired mass was detected as a main peak by LCMS. The reaction mixture was diluted with H2O (15 mL) and extracted with EtOAc (50 mL x 2). The combined organic phase was washed with brine (30 mL x 3), dried over Na2SO4, filtered, and concentrated under reduced pressure. The compound was triturated with (EtOAc:MTBE = 1:1; 40 mL) at 20 °C for 1 hour. The mixture was filtered, and the filter cake was concentrated under reduced pressure and lyophilized to give the title compound (251.3 mg, 296.51 μmol, 48.52% yield, 95.1% purity) as a white solid. MS (M+H)+ =806.6

[0261] [ka]

[0262] The filtrate was concentrated under reduced pressure and purified by prep-HPLC (column: Phenomenex Luna C18 150 x 40 mm x 15 μm; mobile phase: [water (TFA)-ACN]; gradient: 10%-40% B over 10 min, column temperature: 30°C). The eluate was lyophilized to give the title compound (114 mg, 106.61 μmol, 17.45% yield, 96.7% purity, 2% TFA) as a white solid. MS (M+H) + =806.6

[0263] [ka]

[0264] Example 21 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)-[1,4'-bipiperidin]-1'-yl)-3-methoxybenzamide (Compound 21)

[0265] [ka]

[0266] Step 1. Synthesis of tert-butyl 4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidine-1-carboxylate (3) To a solution of 3-(4-aminophenyl)piperidine-2,6-dione (800 mg, 3.92 mmol) in DCM (30 mL) was added tert-butyl 4-formylpiperidine-1-carboxylate (960.00 mg, 4.50 mmol) and HOAc (314.70 mg, 5.24 mmol, 300 μL) at 20 °C, and the mixture was stirred at 20 °C for 1 h. NaBH(OAc) (2.40 g, 11.32 mmol) was then added, and the resulting mixture was stirred at 20 °C for 15 h. LCMS showed the main peak corresponding to the desired mass. The mixture was adjusted to pH 8–9 with NaHCO (sat. aq.) solution at 0 °C and extracted with DCM (30 mL × 3). The combined organic phase was washed with brine (30 mL × 2), dried over NaSO, filtered, and concentrated under reduced pressure. The product was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 40 mm x 15 μm; mobile phase: [water (TFA)-ACN]; gradient: 15%-45% B over 10 min; column temperature: 30°C) to give the title compound (1.4 g, 3.49 mmol, 89.01% yield) as a pale yellow solid. MS (M+Na) + =424.2

[0267] Step 2. Synthesis of 3-(4-((piperidin-4-ylmethyl)amino)phenyl)piperidine-2,6-dione (4) To a solution of tert-butyl 4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)piperidine-1-carboxylate (1 g, 2.49 mmol) in dioxane (2 mL) at 20° C., HCl / dioxane (2 M, 20 mL) was added, and the mixture was stirred at 20° C. for 2 hours. LCMS showed the main peak of the desired mass. The mixture was concentrated under reduced pressure to give the title compound (800 mg, crude, HCl salt) as a pale yellow solid. MS (M+H) + =302.2

[0268] Step 3. Synthesis of 8-nitroso-1,4-dioxa-8-azaspiro[4.5]decane (7) To a solution of 1,4-dioxa-8-azaspiro[4.5]decane (2 g, 13.97 mmol, 1.79 mL) in HO (20 mL) was added NaNO (2.9 g, 42.03 mmol) portionwise at 0 °C, followed by dropwise addition of HOAc (3.36 g, 55.87 mmol, 3.20 mL) at 0 °C, and the mixture was stirred at 20 °C for 16 h. LCMS showed the desired mass as a main peak. The reaction mixture was diluted with HO (20 mL) at 0 °C. The mixture was adjusted to pH 9 with NaHCO (sat. aq.) solution at 0 °C and extracted with EtOAc (50 mL x 3). The combined organic phase was washed with brine (60 mL x 2), dried over NaSO, filtered, and concentrated under reduced pressure to give the title compound (2.4 g, crude) as a pale yellow solid. MS (M+H) + =173.0

[0269] Step 4. Synthesis of 1,4-dioxa-8-azaspiro[4.5]decan-8-amine (8) To a solution of 8-nitroso-1,4-dioxa-8-azaspiro[4.5]decane (2 g, 11.62 mmol) in THF (20 mL) and water (10 mL) was added NH4Cl (3.20 g, 59.82 mmol) at 0 °C under N2, followed by the portionwise addition of Zn (4.10 g, 62.70 mmol) at 0 °C. The suspension was stirred at 20 °C under N2 for 4 h. LCMS confirmed complete consumption of the starting material, and the main peak of the desired mass was detected. The reaction mixture was filtered. The filter cake was washed with THF (50 mL). The filtrate, the title compound (1.8 g, crude, pale yellow oil), was used in the next step without further purification. MS (M+H) + =159.1

[0270] Step 5. Synthesis of tert-butyl (1,4-dioxa-8-azaspiro[4.5]decan-8-yl)carbamate (8A) To a solution of 1,4-dioxa-8-azaspiro[4.5]decan-8-amine (1.8 g, 11.38 mmol) in THF (10 mL) and water (10 mL) was added BocO (7.60 g, 34.82 mmol, 8 mL) under N at 0 °C, followed by portionwise addition of NaCO (5 g, 47.17 mmol) at 0 °C, followed by stirring at 20 °C under N for 14 h. LCMS confirmed complete consumption of 1,4-dioxa-8-azaspiro[4.5]decan-8-amine, and the main peak corresponding to the desired mass was detected. The mixture was filtered. The filtrate was diluted with H2O (30 mL) and extracted with EtOAc (80 mL x 2). The combined organic phase was washed with brine (80 mL x 2), dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (Biotage; 20 g SepaFlash® silica flash column, eluent: 30–50% EtOAc:petroleum ether gradient, 100 mL / min) to afford the title compound (900 mg, 3.48 mmol, 30.62% yield) as a pale yellow solid. MS (M+H −56) + =203.1

[0271] Step 6. Synthesis of 1,4-dioxa-8-azaspiro[4.5]decan-8-amine (8) To a solution of tert-butyl (1,4-dioxa-8-azaspiro[4.5]decan-8-yl)carbamate (600 mg, 2.32 mmol) in DCM (5 mL) was added TFA (4.61 g, 40.39 mmol, 3.00 mL) at 20 °C, and the mixture was stirred at 20 °C for 2 h. LCMS confirmed the main peak of the desired mass. The reaction mixture was concentrated under reduced pressure to give the title compound (600 mg, crude, TFA salt) as a pale yellow oil. MS (M+H) + =159.1

[0272] Step 7. Synthesis of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(1,4-dioxa-8-azaspiro[4.5]decan-8-yl)benzamide (10) To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (600 mg, 1.41 mmol) in DMF (8 mL) was added EDCI (360.00 mg, 1.88 mmol), HOBt (240.00 mg, 1.78 mmol), DIPEA (1.11 g, 8.61 mmol, 1.50 mL), and 1,4-dioxa-8-azaspiro[4.5]decan-8-amine (600.00 mg, 2.20 mmol, TFA salt) at 20 °C under N for 16 h. LCMS showed the desired mass peak (59%). The reaction mixture was diluted with H2O (30 mL) and extracted with EtOAc (50 mL x 2). The combined organic phase was washed with brine (50 mL x 3), dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (Biotage; 10 g SepaFlash® silica flash column, eluent: 60-100% EtOAc:petroleum ether gradient, 80 mL / min) and then repurified by prep-HPLC (column: Phenomenex Luna C18 150 x 40 mm x 15 μm; mobile phase: [water (TFA)-ACN]; gradient: 15%-45% B over 10 min, column temperature: 30 °C). The eluate was lyophilized to afford the title compound (420 mg, 742.49 μmol, 52.65% yield) as a pale yellow solid. MS (M+H) + =566.3

[0273] Step 8. Synthesis of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(4-oxopiperidin-1-yl)benzamide (5) To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(1,4-dioxa-8-azaspiro[4.5]decan-8-yl)benzamide (300 mg, 530.35 μmol) in HO (2 mL) and dioxane (2 mL) was added HCOOH (12 mL). The mixture was stirred at 20 °C for 32 h. LCMS showed a main peak of the desired mass. The reaction mixture was washed with EtOAc (20 mL). The aqueous phase was adjusted to pH 8-9 with Na2CO3 (sat. aq.) at 0 °C, extracted with EtOAc (30 mL x 3). The combined organic phase was washed with brine (30 mL x 2), dried over Na2SO4, filtered, and concentrated under reduced pressure to give the title compound (276 mg, crude) as a pale yellow oil. MS (M+H) + =522.3

[0274] Step 9. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(4-(((4-(2,6-dioxopiperidin-3-yl)phenyl)amino)methyl)-[1,4'-bipiperidin]-1'-yl)-3-methoxybenzamide (Compound 21) To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxy-N-(4-oxopiperidin-1-yl)benzamide (240 mg, 460.11 μmol) in DCM (8 mL) at 20° C., 3-(4-((piperidin-4-ylmethyl)amino)phenyl)piperidine-2,6-dione (200 mg, 591.99 μmol, HCl salt) and TEA (436.20 mg, 4.31 mmol, 600.00 μL) were added, and the mixture was stirred at 20° C. for 6 h. NaBH(OAc) (420.00 mg, 1.98 mmol) was then added, and the mixture was stirred at 20° C. for 15 h. The desired mass peak (25%) was detected by LCMS. The reaction mixture was adjusted to pH 9–10 with NaHCO3 (sat. aq.) solution at 0°C and extracted with DCM (20 mL x 2). The combined organic phase was washed with brine (20 mL x 2), dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (Biotage; 10 g SepaFlash® silica flash column, eluent: 0–10% EtOH:DCM gradient, 60 mL / min) and then repurified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x 10 μm; mobile phase: [water (TFA)-ACN]; gradient: 14%–44% B over 10 min, column temperature: 30°C). The eluate was lyophilized to give the title compound (91.7 mg, 85.05 μmol, 18.48% yield, 96.0% purity, 2% TFA) as a white solid. MS (M+H) + =807.6

[0275] [ka]

[0276] Example 22 Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(1'-(4-(2,6-dioxopiperidin-3-yl)phenethyl)-[1,4'-bipiperidin]-4-yl)-3-methoxybenzamide (Compound 22)

[0277] [ka]

[0278] Step 1. Synthesis of tert-butyl 4-(((benzyloxy)carbonyl)amino)-[1,4'-bipiperidine]-1'-carboxylate (3) To a solution of tert-butyl 4-oxopiperidine-1-carboxylate (2 g, 10.04 mmol) in DCM (30 mL) was added benzyl piperidin-4-ylcarbamate (2.5 g, 10.67 mmol) and HOAc (629.40 mg, 10.48 mmol, 600 μL). The mixture was stirred at 20 °C for 2 h. NaBH(OAc) (4.67 g, 22.02 mmol) was then added at 20 °C, and the resulting mixture was stirred at 20 °C for 14 h. LCMS showed the desired mass peak (59%). The reaction mixture was diluted with HO (10 mL) at 0 °C. The mixture was adjusted to pH 8-9 with NaHCO (sat. aq.) solution at 0 °C, and then extracted with DCM (30 mL × 3). The combined organic phase was extracted with brine (30 mL × 2), dried over NaSO, filtered, and concentrated under reduced pressure. The residue was purified by reverse-phase HPLC (ID 95 mm × H 365 mm Column Welch Ultimate XB_C 18 The mixture was purified using a 20-40 μm column (120 A, mobile phase MeCN / HO, gradient B: 30-50% 45 min, flow rate 100 mL / min, 0.1% FA condition). The eluate was lyophilized to give the title compound (2.6 g, 6.23 mmol, 62.03% yield) as a pale yellow solid. MS (M+H) + =418.2

[0279] Step 2. Synthesis of benzyl [1,4'-bipiperidin]-4-ylcarbamate (4) To a solution of tert-butyl 4-(((benzyloxy)carbonyl)amino)-[1,4'-bipiperidine]-1'-carboxylate (1.0 g, 2.39 mmol) in dioxane (2 mL) was added HCl / dioxane (2 M, 10 mL) at 20°C, followed by stirring at 20°C for 2 hours. LCMS confirmed that tert-butyl 4-(((benzyloxy)carbonyl)amino)-[1,4'-bipiperidine]-1'-carboxylate had been consumed, and the main peak corresponding to the desired mass was detected. The mixture was concentrated under reduced pressure to give the title compound (800 mg, crude, HCl salt) as a pale yellow solid. MS (M+H) + =318.2

[0280] Step 3. Synthesis of benzyl (1'-(4-(2,6-dioxopiperidin-3-yl)phenethyl)-[1,4'-bipiperidin]-4-yl)carbamate (6) To a solution of 2-(4-(2,6-dioxopiperidin-3-yl)phenyl)acetaldehyde (450 mg, 1.95 mmol) in DCM (25 mL) was added benzyl [1,4'-bipiperidin]-4-ylcarbamate (510 mg, 1.44 mmol, HCl salt) and TEA (1.65 g, 16.33 mmol, 2.27 mL) at 20 °C and stirred at 20 °C for 1 h. NaBH(OAc) (1.36 g, 6.43 mmol) was then added, and the resulting mixture was stirred at 20 °C for 15 h. LCMS showed the desired mass peak (24%). The mixture was adjusted to pH 9-10 with NaHCO (sat. aq.) solution at 0 °C and extracted with DCM (40 mL × 2). The combined organic phase was washed with brine (40 mL × 2), dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue was diluted with DMF (7 mL) and filtered. The filter cake was dried to obtain 150 mg of product. The filtrate was purified by prep-HPLC (column: Phenomenex luna C18 150 × 40 mm × 15 μm; mobile phase: [water (TFA)-ACN]; gradient: 0%-30% B over 10 min, Column Temp: 30 °C). The eluate was lyophilized to obtain 450 mg of product. The two batches were combined to obtain the title compound (600 mg, 1.13 mmol, 57.88% yield) as a pale yellow solid. MS (M+H) + =533.3

[0281] Step 4. Synthesis of 3-(4-(2-(4-amino-[1,4'-bipiperidine]-1'-yl)ethyl)phenyl)piperidine-2,6-dione (7) A mixture of benzyl (1'-(4-(2,6-dioxopiperidin-3-yl)phenethyl)-[1,4'-bipiperidin]-4-yl)carbamate (560 mg, 1.05 mmol) in TFA (10 mL) was stirred at 60°C for 3 hours. LCMS confirmed complete consumption of the starting material, and a peak of the desired mass was detected. The mixture was concentrated under reduced pressure to give the title compound (540 mg, crude, TFA salt) as a pale yellow oil. MS (M+H) + =399.3

[0282] Step 5. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(1'-(4-(2,6-dioxopiperidin-3-yl)phenethyl)-[1,4'-bipiperidin]-4-yl)-3-methoxybenzamide (Compound 22) To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (400 mg, 940.12 μmol) in DMF (6 mL) was added EDCI (400 mg, 2.09 mmol), HOBt (200 mg, 1.48 mmol), DIPEA (742.00 mg, 5.74 mmol, 1 mL), and 3-(4-(2-(4-amino-[1,4′-bipiperidine]-1′-yl)ethyl)phenyl)piperidine-2,6-dione (540.00 mg, 1.05 mmol, TFA salt) at 20° C. The mixture was stirred under N for 16 h at 20° C. The desired mass peak (45%) was detected by LCMS. The reaction mixture was diluted with H2O (15 mL) and extracted with EtOAc (40 mL × 2). The combined organic phase was washed with brine (30 mL × 3), dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex luna C18 150 × 40 mm × 15 μm; mobile phase: [water (TFA)-ACN]; gradient: 10%-40% B over 10 min, column temperature: 30 °C). The eluate was lyophilized to give the title compound (194.2 mg, 227.21 μmol, 24.17% yield, 94.3% purity, 2% TFA) as a pale yellow solid, and 90 mg of impure product. This was purified by prep-HPLC (column: Waters Xbridge C18 150 x 50 mm x 10 μm; mobile phase: [water(NH4HCO3)-ACN]; gradient: 25%-55% B over 10 min, column temperature: 30°C). The eluate was lyophilized to give the title compound (46.7 mg, 57.19 μmol, 6.08% yield, 98.7% purity) as a pale yellow solid. MS (M+H) + =806.6

[0283] [ka]

[0284] Example 23 Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(1'-(4-(2,6-dioxopiperidin-3-yl)phenethyl)-[4,4'-bipiperidin]-1-yl)-3-methoxybenzamide (Compound 23)

[0285] [ka]

[0286] Step 1. Synthesis of tert-butyl 1'-nitroso-[4,4'-bipiperidine]-1-carboxylate (2) To a solution of tert-butyl [4,4'-bipiperidine]-1-carboxylate (2 g, 7.45 mmol) in HO (20 mL) was added NaNO (1.54 g, 22.36 mmol) portionwise at 0 °C, followed by dropwise addition of HOAc (2.10 g, 34.94 mmol, 2 mL) at 0 °C. The mixture was stirred at 20 °C for 16 h. LCMS showed the main peak corresponding to the desired mass. The reaction mixture was diluted with HO (20 mL) at 0 °C and adjusted to pH 9 with saturated aqueous NaHCO (60 mL) at 0 °C. The mixture was then extracted with EtOAc (60 mL × 3). The combined organic phase was washed with brine (160 mL × 2, 80 mL), dried over NaSO, and filtered. The filtrate was concentrated under reduced pressure to give the title compound (2.2 g, crude) as a pale yellow oil. MS(M+H-56) + =242.1

[0287] [ka]

[0288] Step 2. Synthesis of tert-butyl 1'-amino-[4,4'-bipiperidine]-1-carboxylate (3) To a solution of tert-butyl 1'-nitroso-[4,4'-bipiperidine]-1-carboxylate (2.1 g, 7.06 mmol) in THF (20 mL) and water (20 mL) was added NH4Cl (2 g, 37.39 mmol) under N2 at 0 °C, followed by portionwise addition of Zn (2.6 g, 39.76 mmol) at 0 °C, and the resulting mixture was stirred for 3 h under N2 at 20 °C. A peak of the desired mass was detected by LCMS. The mixture was filtered. The filter cake was washed with THF (50 mL). The title compound (2 g, crude) as a pale yellow oil was used in the next step without further purification. MS (M+H) + =284.2

[0289] Step 3. Synthesis of tert-butyl 1'-(((benzyloxy)carbonyl)amino)-[4,4'-bipiperidine]-1-carboxylate (4) To a solution of tert-butyl 1'-amino-[4,4'-bipiperidine]-1-carboxylate (2 g, 7.06 mmol) in THF (40 mL) and water (20 mL) was added Na2CO3 (4 g, 37.74 mmol) at 0 °C under N2, followed by dropwise addition of CbzCl (4.80 g, 28.16 mmol, 4.02 mL) at 0 °C and stirring for 16 h under N2 at 20 °C. LCMS confirmed complete consumption of tert-butyl 1'-amino-[4,4'-bipiperidine]-1-carboxylate, and a peak corresponding to the desired mass was detected. The reaction mixture was filtered. The filtrate was diluted with H2O (30 mL) and extracted with EtOAc (60 mL × 2). The combined organic phase was extracted with brine (50 mL × 3), dried over Na2SO4, and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (Biotage; 20 g SepaFlash® silica flash column, eluent: 25-33% EtOAc:petroleum ether gradient, 80 mL / min) and then repurified by prep-HPLC (column: Waters Xbridge C18 150 x 50 mm x 10 μm; mobile phase: [water(NH4HCO3)-ACN]; gradient: 44%-74% B over 10 min, column temp: 30°C). The eluate was lyophilized to afford the title compound (1.8 g, 4.31 mmol, 61.09% yield) as a white solid. MS (M+H) + =418.2

[0290] Step 4. Synthesis of benzyl [4,4'-bipiperidin]-1-ylcarbamate (5) To a solution of tert-butyl 1'-(((benzyloxy)carbonyl)amino)-[4,4'-bipiperidine]-1-carboxylate (1 g, 2.39 mmol) in dioxane (6 mL) was added HCl / dioxane (2 M, 10 mL) at 20°C, and the mixture was stirred at 20°C for 2 hours. LCMS showed a peak corresponding to the desired mass. The mixture was concentrated under reduced pressure to give the title compound (820 mg, crude, HCl salt) as a pale yellow solid. MS (M+H) + =318.2

[0291] Step 5. Synthesis of benzyl (1'-(4-(2,6-dioxopiperidin-3-yl)phenethyl)-[4,4'-bipiperidin]-1-yl)carbamate (7) To a solution of 2-(4-(2,6-dioxopiperidin-3-yl)phenyl)acetaldehyde (550 mg, 2.38 mmol) in DCM (25 mL) was added benzyl [4,4'-bipiperidin]-1-ylcarbamate (700 mg, 1.98 mmol, HCl salt) and TEA (2.04 g, 20.12 mmol, 2.8 mL) at 20 °C and stirred at 20 °C for 1 h. NaBH(OAc) (1.53 g, 7.21 mmol) was then added, and the resulting mixture was stirred at 20 °C for 15 h. LCMS showed the desired mass peak (56%). The reaction mixture was adjusted to pH 9-10 with NaHCO (sat. aq.) solution at 0 °C and extracted with DCM (40 mL × 2). The combined organic phase was washed with brine (30 mL × 2), dried over Na2SO4, filtered, and concentrated under reduced pressure. The residue was diluted with DMF (6 mL) and filtered. The filter cake was dried to obtain 550 mg of product. The filtrate was purified by prep-HPLC (column: Phenomenex luna C18 150 × 25 mm × 10 μm; mobile phase: [water (TFA)-ACN]; gradient: 16% - 46% B over 12 min). The eluate was lyophilized to obtain 120 mg of product. The two batches were combined to obtain the title compound (670 mg, 1.26 mmol, 52.88% yield) as a pale yellow solid. MS (M+H) + =533.3

[0292] Step 6. Synthesis of 3-(4-(2-(1'-amino-[4,4'-bipiperidin]-1-yl)ethyl)phenyl)piperidine-2,6-dione (8) A mixture of benzyl (1'-(4-(2,6-dioxopiperidin-3-yl)phenethyl)-[4,4'-bipiperidin]-1-yl)carbamate (150 mg, 281.60 μmol) in TFA (5 mL) was stirred at 60° C. for 3 hours. LCMS confirmed complete consumption of the starting material, and a peak of the desired mass was detected. The mixture was concentrated under reduced pressure to give the title compound (144 mg, crude, TFA salt) as a pale yellow oil. MS (M+H) + =399.3

[0293] Step 7. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(1'-(4-(2,6-dioxopiperidin-3-yl)phenethyl)-[4,4'-bipiperidin]-1-yl)-3-methoxybenzamide (Compound 23) To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (110 mg, 258.53 μmol) in DMF (3 mL) was added EDCI (100 mg, 521.65 μmol), HOBt (60 mg, 444.04 μmol), DIPEA (296.80 mg, 2.30 mmol, 400 μL), and 3-(4-(2-(1'-amino-[4,4'-bipiperidin]-1-yl)ethyl)phenyl)piperidine-2,6-dione (144 mg, 280.94 μmol, TFA salt) at 20 °C under N for 16 h. The desired mass peak (57%) was detected by LCMS. The reaction mixture was diluted with H2O (5 mL) and extracted with EtOAc (15 mL x 2). The combined organic phase was washed with brine (20 mL x 3), dried over Na2SO4, filtered, and concentrated under reduced pressure. The compound was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x 10 μm; mobile phase: [water (TFA)-ACN]; gradient: 15%-45% B over 12 min, column temperature: 30 °C). The eluate was lyophilized to give the title compound (79.2 mg, 70.92 μmol, 27.43% yield, 92.6% purity, 2% TFA) as a pale yellow solid. MS (M+H) + =806.6

[0294] [ka]

[0295] Example 24 Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(1-(3-(4-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperazin-1-yl)propanoyl)piperidin-4-yl)-3-methoxybenzamide (Compound 24)

[0296] [ka]

[0297] Step 1. Synthesis of 3-((4-(piperazin-1-yl)phenyl)amino)piperidine-2,6-dione (2) To a solution of tert-butyl 4-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperazine-1-carboxylate (1 g, 2.57 mmol) in dioxane (20 mL) was added HCl / dioxane (2 M, 7.72 mL). The mixture was stirred at 25° C. for 8.5 hours. LCMS showed 3% of tert-butyl 4-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperazine-1-carboxylate remaining, with 79% of the desired mass peak detected. The mixture was concentrated under reduced pressure to give the title compound (1.45 g, crude, HCl) as a blue solid. MS (M+H) + =289.2.

[0298] Step 2. Synthesis of tert-butyl (1-(3-(4-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperazin-1-yl)propanoyl)piperidin-4-yl)carbamate (4) To a solution of 3-((4-(piperazin-1-yl)phenyl)amino)piperidine-2,6-dione (1.35 g, 4.16 mmol, HCl) and tert-butyl (1-(3-chloropropanoyl)piperidin-4-yl)carbamate (1.09 g, 3.74 mmol) in DMF (20 mL) was added NaI (747.61 mg, 4.99 mmol) and DIPEA (1.61 g, 12.47 mmol, 2.17 mL). The mixture was stirred at 80 °C for 16 h. LCMS confirmed complete consumption of 3-((4-(piperazin-1-yl)phenyl)amino)piperidine-2,6-dione, with a peak corresponding to 48% of the desired mass. The residue was diluted with HO (100 mL) and extracted with EtOAc (100 mL x 3). The combined organic phase was diluted with brine (200 mL), dried over NaSO, filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (20 g SepaFlash® silica flash column, eluent 100-50% EtOAc / MeOH @ 45 mL / min) to afford the title compound (0.65 g, 1.08 mmol, 25.94% yield, 90% purity) as a purple solid. MS (M+H) + =543.4.

[0299] Step 3. Synthesis of 3-((4-(4-(3-(4-aminopiperidin-1-yl)-3-oxopropyl)piperazin-1-yl)phenyl)amino)piperidine-2,6-dione (5) To a solution of tert-butyl (1-(3-(4-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperazin-1-yl)propanoyl)piperidin-4-yl)carbamate (650 mg, 1.12 mmol, HCl) in dioxane (10 mL) was added HCl / dioxane (2 M, 10 mL). The mixture was stirred at 25° C. for 2 hours. LCMS showed the desired mass peak (63%). The mixture was concentrated under reduced pressure to give the title compound (790 mg, crude, HCl) as a blue solid. MS (M+H) + =443.3.

[0300] Step 4. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-(1-(3-(4-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperazin-1-yl)propanoyl)piperidin-4-yl)-3-methoxybenzamide (Compound 24) To a solution of 3-((4-(4-(3-(4-aminopiperidin-1-yl)-3-oxopropyl)piperazin-1-yl)phenyl)amino)piperidine-2,6-dione (790 mg, 1.65 mmol HCl) and (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (467.81 mg, 1.10 mmol) in DMF (10 mL) was added HATU (543.47 mg, 1.43 mmol) and DIPEA (710.50 mg, 5.50 mmol, 957.55 μL). The mixture was stirred at 25° C. for 2 h. LCMS showed the desired mass peak (42%). The mixture was poured into water (50 mL) and extracted with EtOAc (60 mL x 3). The combined organic phase was extracted with brine (200 mL), dried over Na2SO4, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (ISCO®; 20 g SepaFlash® silica flash column, eluent: 100-30% DCM:MeOH @ 50 mL / min) to give the product. The product was purified by prep-HPLC (column: Waters Xbridge C18 150 x 50 mm x 10 μm; mobile phase: [water(NH4HCO3)-ACN]; gradient: 25%-55% B over 10 min) and lyophilized to give the title compound (203.5 mg, 220.25 μmol, 20.03% yield, 92% purity) as a blue solid. MS (M+H) + =850.5

[0301] [ka]

[0302] Compound 25. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(((1-(6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)piperidin-4-yl)methyl)amino)cyclohexyl)-3-methoxybenzamide (Compound 25)

[0303] [ka]

[0304] Step 1. Synthesis of 1-(6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)piperidine-4-carbaldehyde (2) To a solution of 3-(5-(4-(1,3-dioxolan-2-yl)piperidin-1-yl)pyridin-2-yl)piperidine-2,6-dione (0.5 g, 1.45 mmol) in dioxane (2 mL) and water (2 mL) was added FA (69.55 mg, 1.45 mmol, 6 mL), followed by stirring at 25 °C for 38 h. The mixture was adjusted to pH 8 with Na2CO3 solution at 0 °C and extracted with EtOAc (10 mL x 3). The combined organic phase was washed with water (20 mL), dried over Na2SO4, and filtered. The filtrate was concentrated under reduced pressure to give the title compound (380 mg, crude) as a yellow oil. MS (M+H) + =302.2

[0305] Step 2. Synthesis of tert-butyl ((1r,4r)-4-(((1-(6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)piperidin-4-yl)methyl)amino)cyclohexyl)carbamate (trans) (3) To a solution of 1-(6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)piperidine-4-carbaldehyde (380 mg, 1.26 mmol), tert-butyl ((1r,4r)-4-aminocyclohexyl)carbamate (trans) (0.3 g, 1.40 mmol) in DCM (6 mL) and DMF (3 mL) was added TEA (261.72 mg, 2.59 mmol, 360 μL) and stirred at 25° C. for 15 min. NaBH(OAc) (534.53 mg, 2.52 mmol) was added and the mixture was stirred at 25° C. for 14 h. A peak of the desired mass was detected by LCMS. The mixture was diluted with water (20 mL) and extracted with EtOAc (10 mL x 3). The combined organic phase was washed with water (20 mL), dried over Na2SO4, and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (5 g SepaFlash® silica flash column, eluent: 15% MeOH / EtOAc gradient @ 50 mL / min) to afford the title compound (250 mg, 480.34 μmol, 38.09% yield, 96% purity) as a yellow solid. MS (M+H) + =500.4

[0306] Step 3. Synthesis of 3-(5-(4-((((1r,4r)-4-aminocyclohexyl)amino)methyl)piperidin-1-yl)pyridin-2-yl)piperidine-2,6-dione (trans) (4) To a solution of tert-butyl ((1r,4r)-4-(((1-(6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)piperidin-4-yl)methyl)amino)cyclohexyl)carbamate (trans) (250 mg, 500.36 μmol) in DCM (2.5 mL) was added HCl / dioxane (2 M, 5 mL) and stirred at 25° C. for 1 h. LCMS showed the desired mass peak (93%). The mixture was concentrated under reduced pressure to give the title compound (220 mg, crude, HCl) as a yellow solid. MS (M+H) + =400.3

[0307] Step 4. Synthesis of 4-(((R)-8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-N-((1r,4R)-4-(((1-(6-(2,6-dioxopiperidin-3-yl)pyridin-3-yl)piperidin-4-yl)methyl)amino)cyclohexyl)-3-methoxybenzamide (trans) (Compound 25) To a solution of (R)-4-((8-cyclopentyl-7-ethyl-5-methyl-6-oxo-5,6,7,8-tetrahydropteridin-2-yl)amino)-3-methoxybenzoic acid (210 mg, 493.56 μmol) and HATU (206.43 mg, 542.92 μmol) in DMF (3 mL) was added DIPEA (318.95 mg, 2.47 mmol, 429.85 μL), and the mixture was stirred for 15 min at 25° C. 3-(5-(4-((((1r,4r)-4-aminocyclohexyl)amino)methyl)piperidin-1-yl)pyridin-2-yl)piperidine-2,6-dione (trans) (220 mg, 504.60 μmol, HCl) in DMF (3 mL) was added, and the mixture was stirred at 25° C. for 1 h. LCMS showed a peak of the desired mass (53%). The mixture was diluted with EtOAc (10 mL) and NaHCO3 solution (10 mL), then extracted with EtOAc (10 mL x 3) and DCM (10 mL x 3). The combined organic phase was washed with brine (30 mL x 2), dried over Na2SO4, and filtered. The filtrate was concentrated under reduced pressure and purified by prep-HPLC (column: Phenomenex luna C18 150 x 25 mm x 10 μm; mobile phase: [water (TFA)-ACN]; gradient: 14%-44% B over 10 min), and the eluate was lyophilized. The product was purified by prep-HPLC (column: Waters Xbridge 150*25mm*5um; mobile phase: [water(NH4HCO3)-ACN]; gradient: 30%-50% B over 10 min), and the eluate was lyophilized to give the title compound as a white solid (57.80 mg, 67.33 μmol, 13.64% yield, 94% purity). MS (M+H) + =807.7

[0308] [ka]

[0309] SFC method details: "Column: Chiralpak AD-3 50 x 4.6 mm ID, 3 um; Mobile phase: Phase A for CO2 and Phase B for IPA + ACN (0.05% DEA); Gradient elution: 60% IPA + ACN (0.05% DEA) in CO2; Flow rate: 3 mL / min; Detector: PDA; Column temperature: 35°C; Back pressure: 100 Bar."

[0310] Example 26 Synthesis of 4-((9-cyclopentyl-7,7-difluoro-5-methyl-6-oxo-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,4]diazepin-2-yl)amino)-N-(1-(3-(4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluorophenyl)piperazin-1-yl)propanoyl)piperidin-4-yl)-3-methoxybenzamide (Compound 26)

[0311] [ka]

[0312] Step 1. 3-((3-fluoro-4-(piperazin-1-yl)phenyl)amino)piperidine-2,6-dione (2) To a solution of tert-butyl 4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluorophenyl)piperazine-1-carboxylate (500 mg, 1.23 mmol) in dioxane (5 mL) was added HCl / dioxane (4 M, 5 mL), and the mixture was stirred at 20° C. for 1 hour. LCMS confirmed complete consumption of the starting material, and a peak with the desired mass was detected. The mixture was concentrated under reduced pressure to give the title compound (420 mg, crude, HCl) as a gray solid. MS (M+H) + =307.1.

[0313] Step 2. Synthesis of tert-butyl (1-(3-(4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluorophenyl)piperazin-1-yl)propanoyl)piperidin-4-yl)carbamate (4) To a solution of 3-((3-fluoro-4-(piperazin-1-yl)phenyl)amino)piperidine-2,6-dione (420 mg, crude, HCl), tert-butyl (1-(3-chloropropanoyl)piperidin-4-yl)carbamate (1.78 g, 6.13 mmol) in DMF (10 mL), K2CO3 (677.33 mg, 4.90 mmol), and NaI (18.37 mg, 122.52 μmol) were added and stirred at 90 °C for 16 h. LCMS confirmed complete consumption of the starting material, and a peak with the desired mass was detected. The mixture was diluted with brine (30 mL) and extracted with EtOAc (20 mL × 3). The combined organic phase was washed with brine (80 mL × 3), dried over Na2SO4, and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (Biotage; 20 g SepaFlash® silica flash column, eluent: 50-100% EtOAc / petroleum ether to 10% MeOH / EtOAc gradient @ 100 mL / min) to afford the title compound (630 mg, 1.12 mmol, 91.71% yield) as a gray solid. MS (M+H) + =561.3.

[0314] Step 3. Synthesis of 3-((4-(4-(3-(4-aminopiperidin-1-yl)-3-oxopropyl)piperazin-1-yl)-3-fluorophenyl)amino)piperidine-2,6-dione (5) To a solution of tert-butyl (1-(3-(4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluorophenyl)piperazin-1-yl)propanoyl)piperidin-4-yl)carbamate (630 mg, 1.12 mmol) in dioxane (10 mL) was added HCl / dioxane (4 M, 10 mL), and the mixture was stirred at 20° C. for 0.5 h. LCMS confirmed complete consumption of the starting material, and a peak with the desired mass was detected. The mixture was concentrated under reduced pressure to give the title compound (550 mg, crude, HCl) as a yellow solid. MS (M+H) + =461.2.

[0315] Step 4. Synthesis of 4-((9-cyclopentyl-7,7-difluoro-5-methyl-6-oxo-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,4]diazepin-2-yl)amino)-N-(1-(3-(4-(4-((2,6-dioxopiperidin-3-yl)amino)-2-fluorophenyl)piperazin-1-yl)propanoyl)piperidin-4-yl)-3-methoxybenzamide (Compound 26) To a solution of 4-((9-cyclopentyl-7,7-difluoro-5-methyl-6-oxo-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,4]diazepin-2-yl)amino)-3-methoxybenzoic acid (270.08 mg, 603.62 μmol) in DMF (6 mL) was added HATU (344.27 mg, 905.42 μmol), DIPEA (390.07 mg, 3.02 mmol, 525.70 μL), and the mixture was stirred at 20° C. for 0.5 h. 3-((4-(4-(3-(4-aminopiperidin-1-yl)-3-oxopropyl)piperazin-1-yl)-3-fluorophenyl)amino)piperidine-2,6-dione (300 mg, crude, HCl) was added and stirred at 20° C. for 16 hours. LCMS confirmed that the starting material was completely consumed, and a peak of the desired mass was detected. The reaction mixture was diluted with brine (15 mL) and extracted with EtOAc (20 mL×3). The combined organic phase was washed with brine (80 mL×3), dried over Na2SO4, and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (Biotage; 10 g SepaFlash® silica flash column, eluent: 50–100% EtOAc / petroleum ether to 10% MeOH / EtOAc gradient @ 200 mL / min) and then repurified by reverse-phase HPLC (column: Waters Xbridge 150×25 mm×5 μm; mobile phase: [water(NH4HCO3)-ACN]; B%: 36%–66%, 10 min). The eluate was lyophilized to afford the title compound (200.9 mg, 218.97 μmol, 36.28% yield, 97% purity) as a gray solid. MS (M+H) + =890.3.

[0316] [ka]

[0317] Compound 27. Synthesis of 4-((9-cyclopentyl-7,7-difluoro-5-methyl-6-oxo-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,4]diazepin-2-yl)amino)-N-((1-((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)piperidin-4-yl)methyl)-3-methoxybenzamide (Compound 27)

[0318] [ka]

[0319] Step 1. Synthesis of ethyl 1-(4-(2,6-bis(benzyloxy)pyridin-3-yl)phenyl)piperidine-4-carboxylate (3) A mixture of 2,6-bis(benzyloxy)-3-(4-bromophenyl)pyridine (1.9 g, 4.26 mmol), ethyl piperidine-4-carboxylate (803.07 mg, 5.11 mmol), RuPhos (198.64 mg, 425.69 μmol), Pd(dba) (389.81 mg, 425.69 μmol), and CsCO (4.16 g, 12.77 mmol) in dioxane (40 mL) was degassed and purged with N three times, then stirred at 100 °C under N for 16 h. LCMS showed the desired mass peak (75%). The mixture was filtered through a pad of Celite. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (Biotage; 20 g SepaFlash® silica flash column, eluent: 0-20% EtOAc / petroleum ether gradient @ 100 mL / min) to afford the title compound (1.9 g, 3.64 mmol, 85.40% yield) as a white solid. MS (M+H) + =523.2

[0320] Step 2. Synthesis of (1-(4-(2,6-bis(benzyloxy)pyridin-3-yl)phenyl)piperidin-4-yl)methanol (5) To a solution of ethyl 1-(4-(2,6-bis(benzyloxy)pyridin-3-yl)phenyl)piperidine-4-carboxylate (1.1 g, 2.10 mmol) in THF (20 mL) was added LAH (160 mg, 4.22 mmol) at 0 °C, followed by stirring at 25 °C for 2 h. LCMS showed the main peak of the desired mass. The mixture was quenched by adding HO (0.5 mL), NaOH (15% aq, 0.5 mL), and HO (1.5 mL), dried over NaSO, and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (Biotage; 20 g SepaFlash® silica flash column, eluent: 0-50% EtOAc / petroleum ether gradient @ 100 mL / min) to afford the title compound (0.9 g, 1.87 mmol, 88.97% yield) as a white solid. MS (M+H) + =481.2

[0321] Step 3. Synthesis of 3-(4-(4-(hydroxymethyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (6) A mixture of (1-(4-(2,6-bis(benzyloxy)pyridin-3-yl)phenyl)piperidin-4-yl)methanol (800 mg, 1.66 mmol) and Pd / C (200 mg, 1.66 mmol, 10% purity) in CF3CH2OH (10 mL) and THF (2 mL) was degassed, purged with H2 (15 psi) three times, and stirred at 20 °C for 16 h. LCMS showed a main peak with the desired mass. The mixture was filtered through a Celite pad. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (Biotage; 20 g SepaFlash® silica flash column, eluent: 50-100% EtOAc / petroleum ether gradient @ 100 mL / min) to give the title compound (480 mg, 1.59 mmol, 95.37% yield) as a white solid. MS (M+H) + =303.1

[0322] Step 4. Synthesis of 1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidine-4-carbaldehyde (7) To a solution of 3-(4-(4-(hydroxymethyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (200 mg, 661.45 μmol) in DCM (1 mL) was added DMP (336.66 mg, 793.74 μmol), and the mixture was stirred at 20° C. for 1 hour. LCMS showed a peak corresponding to the desired mass. The mixture was filtered through a pad of Celite. The filtrate was concentrated under reduced pressure to give the title compound (200 mg, crude) as a brown oil. MS (M+H) + =301.1

[0323] Step 5. Synthesis of tert-butyl ((1-((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)piperidin-4-yl)methyl)carbamate (9) A mixture of 1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidine-4-carbaldehyde (200 mg, crude), tert-butyl (piperidin-4-ylmethyl)carbamate (142.70 mg, 665.89 μmol) in DCM (2 mL) was stirred at 20 °C for 0.5 h, followed by addition of NaBH(OAc) (423.39 mg, 2.00 mmol) and stirring at 20 °C for 16 h. LCMS showed the desired mass peak (98%). The reaction mixture was quenched with NaHCO (5 mL) and extracted with EtOAc (10 mL × 3). The combined organic phase was washed with brine (20 mL × 2), dried over NaSO, filtered, and the filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (Biotage; 10 g SepaFlash® silica flash column, eluent: 50-100% EtOAc / petroleum ether to 10% MeOH / EtOAc gradient @ 100 mL / min), followed by trituration with a mixture (6 mL, DMF:ACN=5:1) at 20°C for 0.5 hours. The filter cake was dried in vacuo to afford the title compound (74 mg, 148.40 μmol, 37.00% yield, 78% purity) as a purple solid. The filtrate was purified again by prep-HPLC (column: Phenomenex Synergi Polar-RP 100 x 25 mm x 4 μm; mobile phase: [water (TFA)-ACN]; B%: 10%-40%, 9 min), and the eluate was lyophilized to give the title compound as a white solid (130 mg, 260.70 μmol, 65.00% yield, 93% purity). MS (M+H) + =499.3

[0324] Step 6. Synthesis of 3-(4-(4-((4-(aminomethyl)piperidin-1-yl)methyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (10) To a solution of tert-butyl ((1-((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)piperidin-4-yl)methyl)carbamate (130 mg, 212.18 μmol, TFA salt) in DCM (2 mL) was added TFA (241.94 mg, 2.12 mmol) at 20° C. The mixture was stirred at 20° C. for 20 minutes. LCMS confirmed that the starting material had been consumed and a peak of the desired mass was detected. The mixture was concentrated under reduced pressure to give the title compound (109 mg, crude, TFA) as a yellow oil. MS (M+H) + =399.3

[0325] Step 7. Synthesis of 4-((9-cyclopentyl-7,7-difluoro-5-methyl-6-oxo-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,4]diazepin-2-yl)amino)-N-((1-((1-(4-(2,6-dioxopiperidin-3-yl)phenyl)piperidin-4-yl)methyl)piperidin-4-yl)methyl)-3-methoxybenzamide (Compound 27) A solution of 4-((9-cyclopentyl-7,7-difluoro-5-methyl-6-oxo-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,4]diazepin-2-yl)amino)-3-methoxybenzoic acid (70 mg, 156.45 μmol) in DMF (2 mL) was incubated at 20 °C with HATU (65.43 mg, 172.09 μmol) and DIPEA (60.66 mg, 469 μmol). After stirring for 10 min, a solution of 3-(4-(4-((4-(aminomethyl)piperidin-1-yl)methyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (109 mg, crude, TFA salt) in DMF (2 mL) and DIPEA (121.32 mg, 938.69 μmol) was added at 20 °C, and the resulting mixture was stirred at 20 °C for 1 h. LCMS confirmed that the starting material was consumed, and a peak of the desired mass (90%) was detected. The mixture was diluted with water (15 mL) and extracted with EtOAc (10 mL × 3). The combined organic phase was washed with brine (10 mL × 3), dried over Na SO , filtered, and concentrated under reduced pressure. The residue was purified by prep-TLC (SiO , DCM:MeOH = 10:1) to obtain the residue. The residue was mixed with another batch (30 mg scale) and lyophilized to give the title compound (113 mg, 136.48 μmol, 87.24% yield) as a white solid. MS (M+H) + =828.2

[0326] [ka]

[0327] Example 28 Synthesis of 4-((9-cyclopentyl-7,7-difluoro-5-methyl-6-oxo-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,4]diazepin-2-yl)amino)-N-((1-((1-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperidin-4-yl)methyl)piperidin-4-yl)methyl)-3-methoxybenzamide (Compound 28)

[0328] [ka]

[0329] Step 1. Synthesis of benzyl 4-((4-(((tert-butoxycarbonyl)amino)methyl)piperidin-1-yl)methyl)piperidine-1-carboxylate (3) To a solution of benzyl 4-formylpiperidine-1-carboxylate (10 g, 40.44 mmol) and tert-butyl (piperidin-4-ylmethyl)carbamate (8.67 g, 40.44 mmol) in MeOH (200 mL) was added AcOH (2.43 g, 40.44 mmol, 2.31 mL) at 20 °C. After stirring for 30 min, NaBHCN (2.54 g, 40.44 mmol) was slowly added at 20 °C and stirred for 16 h at 20 °C. LCMS confirmed complete consumption of the starting material, and the desired mass peak (62%) was detected. The reaction mixture was diluted with H2O (300 mL) and extracted with EtOAc (150 mL x 3). The combined organic phase was washed with NaHCO3 (100 mL x 3), dried over Na2SO4, and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (80 g SepaFlash® silica flash column, eluting with a 0-100% EtOAc / petroleum ether gradient at 200 mL / min) and then repurified by flash silica gel chromatography (ISCO®; 80 g SepaFlash® silica flash column, eluting with a 0-100% EtOAc / petroleum ether gradient at 200 mL / min) to afford the title compound (14 g, 31.42 mmol, 77.70% yield) as a white solid. MS (M+H) + =446.4.

[0330] Step 2. Synthesis of tert-butyl ((1-(piperidin-4-ylmethyl)piperidin-4-yl)methyl)carbamate (4) To a solution of benzyl 4-((4-(((tert-butoxycarbonyl)amino)methyl)piperidin-1-yl)methyl)piperidine-1-carboxylate (2 g, 4.49 mmol) in EtOH (20 mL) under N was added Pd / C (1 g, 10% purity) and AcOH (2.10 g, 34.94 mmol, 2 mL). The suspension was degassed and purged with H three times. Stirred at 25 °C under H (50 Psi) for 16 h. LCMS showed starting material remained, and the mixture was stirred at 20 °C for an additional 16 h. LCMS showed half of the starting material remained. Additional Pd(OH) / C (1 g, 20% purity), AcOH (1 mL) were added, and the suspension was degassed and purged with H three times. The mixture was stirred at 25 °C under H (50 Psi) for 16 h. LCMS confirmed that the starting material had been consumed, and a peak of the desired mass (86%) was detected. The reaction mixture was filtered. The filter cake was washed with EtOH (40 mL x 3), and the filtrate was concentrated under reduced pressure to give the title compound (1.5 g, crude) as a colorless oil. MS (M+H) + =312.5.

[0331] Step 3. Synthesis of tert-butyl ((1-((1-(4-nitrophenyl)piperidin-4-yl)methyl)piperidin-4-yl)methyl)carbamate (5) To a solution of tert-butyl ((1-(piperidin-4-ylmethyl)piperidin-4-yl)methyl)carbamate (1.5 g, 4.04 mmol) and 1-fluoro-4-nitrobenzene (455.76 mg, 3.23 mmol, 342.67 μL) in DMSO (40 mL) was added K2CO3 (2.23 g, 16.15 mmol) at 20 °C. The mixture was stirred at 20 °C for 16 h. LCMS showed the desired mass peak (26%). The reaction mixture was diluted with H2O (80 mL) and extracted with EtOAc (30 mL × 3). The combined organic phase was washed with brine (30 mL × 3), dried over Na2SO4, and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (80 g SepaFlash® silica flash column, eluent: 0-100% EtOAc / petroleum ether gradient @ 200 mL / min) to afford the title compound (400 mg, 924.74 μmol, 22.90% yield) as a yellow oil. MS (M+H) + =433.3.

[0332] Step 4. Synthesis of tert-butyl ((1-((1-(4-aminophenyl)piperidin-4-yl)methyl)piperidin-4-yl)methyl)carbamate (6) To a solution of tert-butyl ((1-((1-(4-nitrophenyl)piperidin-4-yl)methyl)piperidin-4-yl)methyl)carbamate (400 mg, 924.74 μmol) in EtOH (10 mL) and HO (2 mL) was added Fe (258.23 mg, 4.62 mmol) and NH4Cl (247.32 mg, 4.62 mmol) at 20 °C. The mixture was stirred at 80 °C for 2 h. LCMS showed that most of the starting material remained, so additional NH4Cl (247.33 mg, 4.62 mmol) was added, and the reaction mixture was stirred at 80 °C for 1 h. LCMS showed that 11% of the starting material remained, with the desired mass peak (83%) detected. The reaction mixture was diluted with HO (40 mL), adjusted to pH = 10 with Na2CO3, and extracted with EtOAc (30 mL x 3). The combined organic phase was dried over Na2SO4 and filtered. The filtrate was concentrated under reduced pressure to give the title compound (370 mg, crude) as a brown oil. MS (M+H) + =403.3.

[0333] Step 5. Synthesis of tert-butyl ((1-((1-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperidin-4-yl)methyl)piperidin-4-yl)methyl)carbamate (8) To a solution of tert-butyl ((1-((1-(4-aminophenyl)piperidin-4-yl)methyl)piperidin-4-yl)methyl)carbamate (185 mg, 459.55 μmol) and 3-bromopiperidine-2,6-dione (264.71 mg, 1.38 mmol) in ACN (1.5 mL) was added NaHCO (231.63 mg, 2.76 mmol, 107.29 μL) at 20 °C. The mixture was stirred at 80 °C for 16 h. LCMS confirmed complete consumption of the starting material, and a peak of the desired mass (36%) was detected. The reaction mixture was filtered, and the filter cake was washed with EtOAc (20 mL). The filtrate was concentrated under reduced pressure to obtain the product. The product was combined with another batch (350 mg scale). The residue was purified by flash silica gel chromatography (12 g SepaFlash® silica flash column, eluent: 0-100% EtOAc / petroleum ether to 0-50% DCM / MeOH gradient @ 100 mL / min) to give product A (248 mg). Product A was re-purified by prep-TLC (SiO2, DCM:MeOH = 5:1) to give an impure product, which was dissolved in a mixture (20 mL, ACN:HO = 1:3) to give the title compound (170 mg, 330.95 μmol, 72.02% yield) as a white solid. MS (M+H) + =514.3.

[0334] Step 6. Synthesis of 3-((4-(4-((4-(aminomethyl)piperidin-1-yl)methyl)piperidin-1-yl)phenyl)amino)piperidine-2,6-dione (9) To a solution of tert-butyl ((1-((1-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperidin-4-yl)methyl)piperidin-4-yl)methyl)carbamate (138 mg, 268.65 μmol) in DCM (1 mL) was added TFA (307.00 mg, 2.69 mmol, 0.2 mL) and stirred at 20° C. for 1 h. LCMS confirmed complete consumption of the starting material, and a peak with the desired mass was detected. The reaction mixture was concentrated under reduced pressure to give the title compound (228 mg, crude, TFA salt) as a dark green solid. MS (M+H)+ =414.4.

[0335] Step 7. Synthesis of 4-((9-cyclopentyl-7,7-difluoro-5-methyl-6-oxo-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,4]diazepin-2-yl)amino)-N-((1-((1-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperidin-4-yl)methyl)piperidin-4-yl)methyl)-3-methoxybenzamide (Compound 28) A solution of 4-((9-cyclopentyl-7,7-difluoro-5-methyl-6-oxo-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,4]diazepin-2-yl)amino)-3-methoxybenzoic acid (96.68 mg, 216.08 μmol) in DMF (1 mL) was incubated at 20 °C with HATU (98.59 mg, 259.30 μmol) and DIPEA (74.20 mg, 574.11 μmol). After stirring for 10 min at 20 °C, a solution of 3-((4-(4-((4-(aminomethyl)piperidin-1-yl)methyl)piperidin-1-yl)phenyl)amino)piperidine-2,6-dione (114 mg, 216.08 μmol, TFA salt) in DMF (1 mL) and DIPEA (222.60 mg, 1.72 mmol, 0.3 mL) was added and stirred at 20 °C for 1 h. LCMS confirmed complete consumption of the starting material, and the peak of the desired mass (26%) was detected. The reaction mixture was diluted with HO (20 mL) and extracted with EtOAc (10 mL × 3). The combined organic phase was washed with brine (10 mL × 3), dried over NaSO, filtered, and concentrated under reduced pressure. The product was purified by prep-TLC (SiO2, DCM:MeOH = 5:1) and re-purified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x 10 μm; mobile phase: [water (TFA)-ACN]; gradient: 18% - 48% B over 9 min). The eluate was lyophilized to give the title compound (31.1 mg, 27.91 μmol, 12.91% yield, 96.2% purity, 2% TFA) as a white solid. MS (M+H) + =843.4.

[0336] [ka]

[0337] Example 29 Synthesis of 4-((9'-cyclopentyl-5'-methyl-6'-oxo-5',6',8',9'-tetrahydrospiro[cyclopropane-1,7'-pyrimido[4,5-b][1,4]diazepin]-2'-yl)amino)-N-(1-(3-(4-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperazin-1-yl)propanoyl)piperidin-4-yl)-3-methoxybenzamide (Compound 29)

[0338] [ka]

[0339] Step 1. Synthesis of tert-butyl 4-(4-nitrophenyl)piperazine-1-carboxylate (3) To a solution of 1-fluoro-4-nitrobenzene (10 g, 70.87 mmol, 7.52 mL) and tert-butyl piperazine-1-carboxylate (26.40 g, 141.74 mmol) in DMF (100 mL) was added K2CO3 (29.38 g, 212.62 mmol). The mixture was stirred at 0 °C for 1 h and then at 20 °C for 16 h. LCMS confirmed complete consumption of 1-fluoro-4-nitrobenzene, and a peak of the desired mass was detected. The mixture was diluted with H2O (100 mL) at 0 °C. The mixture was filtered and washed with water (100 mL) and petroleum ether (100 mL) to give the title compound (25.7 g, crude) as a yellow solid. MS (M+H) + =308.0.

[0340] Step 2. Synthesis of tert-butyl 4-(4-aminophenyl)piperazine-1-carboxylate (4) To a solution of tert-butyl 4-(4-nitrophenyl)piperazine-1-carboxylate (10 g, crude) in EtOH (100 mL) was added Pd / C (3 g, 10% purity). The suspension was degassed and purged with H2 three times. The mixture was stirred at 25 °C under H2 (15 Psi) for 16 h. LCMS confirmed complete consumption of tert-butyl 4-(4-nitrophenyl)piperazine-1-carboxylate, and a peak with the desired mass was detected. The mixture was filtered and concentrated under reduced pressure to give the title compound (9.18 g, crude) as a red solid. The product was used in the next step without further purification. MS (M+H) + =278.2.

[0341] Step 3. Synthesis of tert-butyl 4-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperazine-1-carboxylate (6) To a solution of tert-butyl 4-(4-aminophenyl)piperazine-1-carboxylate (2.5 g, 9.01 mmol) and 3-bromopiperidine-2,6-dione (3.46 g, 18.02 mmol) in ACN (10 mL) was added NaHCO (3.51 g, 41.78 mmol, 1.63 mL). The mixture was stirred at 80 °C for 16 h. LCMS confirmed complete consumption of tert-butyl 4-(4-aminophenyl)piperazine-1-carboxylate, and a peak corresponding to the desired mass was detected. The reaction mixture was quenched with HO (40 mL) at 25 °C and then extracted with EtOAc (160 mL). The combined organic phase was dried over NaSO, filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (ISCO®; 80 g SepaFlash® silica flash column, eluent: 0-40% EtOAc / petroleum ether gradient @ 50 mL / min) to afford the title compound (1.7 g, 4.38 mmol, 48.55% yield) as a blue solid. MS (M+H) + =389.2.

[0342] Step 4. Synthesis of 3-((4-(piperazin-1-yl)phenyl)amino)piperidine-2,6-dione (7) To a solution of tert-butyl 4-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperazine-1-carboxylate (0.6 g, 1.54 mmol) in DCM (6 mL) was added TFA (3.07 g, 26.92 mmol, 2 mL). The mixture was stirred at 20° C. for 1 h. LCMS confirmed complete consumption of tert-butyl 4-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperazine-1-carboxylate, and a peak of the desired mass was detected. The mixture was concentrated under reduced pressure to give the title compound (0.62 g, 1.54 mmol, 99.76% yield, TFA) as a blue oil. MS (M+H) + =289.3.

[0343] Step 5. Synthesis of tert-butyl (1-(3-(4-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperazin-1-yl)propanoyl)piperidin-4-yl)carbamate (9) To a solution of 3-((4-(piperazin-1-yl)phenyl)amino)piperidine-2,6-dione (0.77 g, 1.91 mmol, TFA) and tert-butyl (1-(3-chloropropanoyl)piperidin-4-yl)carbamate (1.11 g, 3.83 mmol) in DMF (8 mL) was added DIPEA (2.23 g, 17.22 mmol, 3.00 mL) and NaI (57.37 mg, 382.73 μmol). The mixture was stirred at 40 °C for 16 h. LCMS showed 23% of 3-((4-(piperazin-1-yl)phenyl)amino)piperidine-2,6-dione remaining and 16% of the desired mass peak. The reaction mixture was quenched with HO (20 mL) at 25 °C and extracted with EtOAc (180 mL). The combined organic phase was washed with brine (20 mL), dried over NaSO, filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (ISCO®; 40 g SepaFlash® silica flash column, eluent 0-10% MeOH / EtOAc @ 50 mL / min) to afford the title compound (0.34 g, 626.53 μmol, 32.74% yield) as a black solid. MS (M+H) + =543.4.

[0344] Step 6. Synthesis of 3-((4-(4-(3-(4-aminopiperidin-1-yl)-3-oxopropyl)piperazin-1-yl)phenyl)amino)piperidine-2,6-dione (10) To a solution of tert-butyl (1-(3-(4-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperazin-1-yl)propanoyl)piperidin-4-yl)carbamate (300 mg, 552.82 μmol) in DCM (0.4 mL) was added TFA (1.15 g, 10.10 mmol, 750.00 μL). The mixture was stirred at 25° C. for 0.5 h. LCMS confirmed complete consumption of tert-butyl (1-(3-(4-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperazin-1-yl)propanoyl)piperidin-4-yl)carbamate, and a peak of the desired mass was detected. The mixture was concentrated under reduced pressure to give the title compound (300 mg, 539.01 μmol, 97.50% yield, TFA) as a green oil. MS (M+H) + =443.2.

[0345] Step 7. Synthesis of 4-((9'-cyclopentyl-5'-methyl-6'-oxo-5',6',8',9'-tetrahydrospiro[cyclopropane-1,7'-pyrimido[4,5-b][1,4]diazepin]-2'-yl)amino)-N-(1-(3-(4-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperazin-1-yl)propanoyl)piperidin-4-yl)-3-methoxybenzamide (Compound 29) To a solution of 4-((9'-cyclopentyl-5'-methyl-6'-oxo-5',6',8',9'-tetrahydrospiro[cyclopropane-1,7'-pyrimido[4,5-b][1,4]diazepin]-2'-yl)amino)-3-methoxybenzoic acid (235.81 mg, 539.01 μmol) in DMF (3 mL) was added HATU (307.42 mg, 808.51 μmol) and DIPEA (348.32 mg, 2.70 mmol, 469.43 μL). The mixture was stirred at 25° C. for 0.5 h. Then, 3-((4-(4-(3-(4-aminopiperidin-1-yl)-3-oxopropyl)piperazin-1-yl)phenyl)amino)piperidine-2,6-dione (300 mg, 539.01 μmol, TFA) was added and stirred at 25° C. for 16 hours. LCMS confirmed that 11% of 3-((4-(4-(3-(4-aminopiperidin-1-yl)-3-oxopropyl)piperazin-1-yl)phenyl)amino)piperidine-2,6-dione remained, and 24% of the desired mass peak was detected. DIPEA (371.00 mg, 2.87 mmol, 0.5 mL) was added and stirred at 25° C. for 2 hours. LCMS confirmed complete consumption of 3-((4-(4-(3-(4-aminopiperidin-1-yl-3-oxopropyl)piperazin-1-yl)phenyl)amino)piperidine-2,6-dione, and a peak of the desired mass was detected. The reaction mixture was quenched with HO (20 mL) at 25 °C and extracted with EtOAc (40 mL x 3). The combined organic phase was washed with brine (20 mL), dried over NaSO, filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (ISCO®; 20 g SepaFlash® silica flash column, eluent 0-20% MeOH / EtOAc @ 50 mL / min) and prep-HPLC (column: Waters Xbridge 150*25 mm*5 μm; mobile phase: [water(NH4HCO3)-ACN]; gradient: 30%-60% B over The mixture was re-purified by filtration for 10 min.The eluate was lyophilized to give 4-((9'-cyclopentyl-5'-methyl-6'-oxo-5',6',8',9'-tetrahydrospiro[cyclopropane-1,7'-pyrimido[4,5-b][1,4]diazepin]-2'-yl)amino)-N-(1-(3-(4-(4-((2,6-dioxopiperidin-3-yl)amino)phenyl)piperazin-1-yl)propanoyl)piperidin-4-yl)-3-methoxybenzamide (73 mg, 79.60 μmol, 14.77% yield, 94% purity) and the title compound (50.2 mg, 56.49 μmol, 10.48% yield, 94% purity) as a purple solid. MS (M+H). + =862.7.

[0346] [ka]

[0347] Example 30 Synthesis of 4-((9-cyclopentyl-7,7-difluoro-5-methyl-6-oxo-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,4]diazepin-2-yl)amino)-N-((1r,4r)-4-(((1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperidin-4-yl)methyl)amino)cyclohexyl)-3-methoxybenzamide (Compound 30)

[0348] [ka]

[0349] Step 1. Synthesis of 1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperidine-4-carbaldehyde (2) To a solution of 3-(3-fluoro-4-(4-(hydroxymethyl)piperidin-1-yl)phenyl)piperidine-2,6-dione (2 g, 6.24 mmol) in DCM (50 mL) was added DMP (3.97 g, 9.36 mmol), and the mixture was stirred at 20 °C for 2 h. TLC (petroleum ether / EtOAc = 1 / 1) confirmed complete consumption of 3-(3-fluoro-4-(4-(hydroxymethyl)piperidin-1-yl)phenyl)piperidine-2,6-dione and the formation of a new spot. The mixture was filtered, and the filtrate was concentrated under reduced pressure to give the title compound (2 g, crude) as a yellow oil. MS (M+H) + =319.4

[0350] Step 2. Synthesis of benzyl ((1r,4r)-4-(((1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperidin-4-yl)methyl)amino)cyclohexyl)carbamate (4) To a solution of 1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperidine-4-carbaldehyde (2 g, 6.28 mmol) and benzyl ((1r,4r)-4-aminocyclohexyl)carbamate (1.56 g, 6.28 mmol) in DCM (20 mL) was added AcOH (377.28 mg, 6.28 mmol, 359.66 μL). After stirring at 20 °C for 1 h, NaBH(OAc) (1.60 g, 7.54 mmol) was added and the resulting mixture was stirred at 20 °C for 12 h. LCMS showed the desired mass peak (43%). The mixture was diluted with water (100 mL) and extracted with DCM (50 mL × 3). The combined organic phase was washed with brine (200 mL), dried over Na SO , filtered, and concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 40 mm x 15 μm; mobile phase: [water (TFA)-ACN]; gradient: 15%-45% B over 10 min) to give the title compound as a yellow oil (0.9 g, 1.57 mmol, 24.97% yield, 96% purity). MS (M+H) + =551.4

[0351] Step 3. Synthesis of 3-(4-(4-((((1r,4r)-4-aminocyclohexyl)amino)methyl)piperidin-1-yl)-3-fluorophenyl)piperidine-2,6-dione (5) A mixture of benzyl ((1r,4r)-4-(((1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperidin-4-yl)methyl)amino)cyclohexyl)carbamate (450 mg, 817.20 μmol) in TFA (7.68 g, 67.31 mmol, 5 mL) was stirred at 40° C. for 3 hours. LCMS showed the desired mass peak (79%). The mixture was concentrated under reduced pressure to give the title compound (0.4 g, 753.93 μmol, 92.26% yield, TFA) as a yellow oil. MS (M+H) + =417.3

[0352] Step 4. Synthesis of 4-((9-cyclopentyl-7,7-difluoro-5-methyl-6-oxo-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,4]diazepin-2-yl)amino)-N-((1r,4r)-4-(((1-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperidin-4-yl)methyl)amino)cyclohexyl)-3-methoxybenzamide (Compound 30) A solution of 4-((9-cyclopentyl-7,7-difluoro-5-methyl-6-oxo-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,4]diazepin-2-yl)amino)-3-methoxybenzoic acid (168.67 mg, 376.96 μmol) in DMF (5 mL) was treated with HATU (172.00 mg, 452.36 μmol) and DIPEA (194.8 After stirring at 20° C. for 1 hour, 3-(4-(4-((((1r,4r)-4-aminocyclohexyl)amino)methyl)piperidin-1-yl)-3-fluorophenyl)piperidine-2,6-dione (0.2 g, 376.96 μmol, TFA salt) was added and the resulting mixture was stirred at 20° C. for 12 hours. LCMS showed the desired mass peak (16%). The reaction mixture was diluted with water (50 mL) and extracted with EtOAc (30 mL×3). The combined organic phase was washed with brine (100 mL), dried over Na2SO4, and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x 10 μm; mobile phase: [water (FA)-ACN]; gradient: 17% - 47% B over 10 min), and the eluate was lyophilized to give the title compound (17.5 mg, 20.25 μmol, 5.37% yield, 97.9% purity) as a pale yellow solid. MS (M+H) + =846.4.

[0353] [ka]

[0354] Example 31 Synthesis of N-(4-(1-amino-2-(4-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-4-((7,7-difluoro-9-isopropyl-5-methyl-6-oxo-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,4]diazepin-2-yl)amino)-3-methoxybenzamide (Compound 31)

[0355] [ka]

[0356] Step 1. Synthesis of tert-butyl 4-(1-(((benzyloxy)carbonyl)amino)-2-methoxy-2-oxoethyl)piperidine-1-carboxylate (2) To a solution of tert-butyl 4-(1-amino-2-methoxy-2-oxoethyl)piperidine-1-carboxylate (4.5 g, 16.52 mmol) in THF (50 mL) was added CbzCl (3.38 g, 19.83 mmol, 2.83 mL) and K2CO3 (6.85 g, 49.57 mmol). The mixture was stirred at 20 °C for 16 h. LCMS confirmed complete consumption of the starting material, and a peak of the desired mass (15%) was detected. The mixture was quenched with water (30 mL) at 0 °C and extracted with EtOAc (50 mL × 2). The combined organic phase was washed with brine (40 mL), dried over Na2SO4, and filtered. The filtrate was concentrated under reduced pressure and purified by flash silica gel chromatography (40 g SepaFlash® silica flash column, eluent: 0-30% EtOAc / petroleum ether gradient @ 60 mL / min) to afford the title compound (3.9 g, 9.59 mmol, 58.07% yield) as a colorless oil. MS (M-100+H) + =307.2

[0357] Step 2. Synthesis of tert-butyl 4-(1-(((benzyloxy)carbonyl)amino)-2-hydroxyethyl)piperidine-1-carboxylate (3) To a solution of tert-butyl 4-(1-(((benzyloxy)carbonyl)amino)-2-methoxy-2-oxoethyl)piperidine-1-carboxylate (3.9 g, 9.59 mmol) in THF (100 mL) was added LiBH (2 M, 9.59 mL) at 0 °C. The mixture was stirred at 20 °C for 16 h. LCMS confirmed complete consumption of the starting material, and a peak corresponding to 37% of the desired mass was detected. The reaction mixture was quenched with NH Cl (30 mL) solution at 0 °C and extracted with EtOAc (40 mL × 2). The combined organic phase was washed with brine (30 mL), dried over Na SO , filtered, and concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (40 g SepaFlash® silica flash column, eluent: 0 to 60% EtOAc / petroleum ether gradient @ 60 mL / min) to afford the title compound (1.5 g, 3.73 mmol, 38.83% yield, 94% purity) as a colorless oil. MS (M-100+H) + =279.2

[0358] Step 3. Synthesis of tert-butyl 4-(1-(((benzyloxy)carbonyl)amino)-2-oxoethyl)piperidine-1-carboxylate (4) To a solution of DMSO (420.00 mg, 5.38 mmol, 420 μL) in DCM (9 mL) was slowly added (COCl) (609.00 mg, 4.80 mmol, 420 μL) at −70° C., followed by stirring at −70° C. for 15 minutes. A solution of tert-butyl 4-(1-(((benzyloxy)carbonyl)amino)-2-hydroxyethyl)piperidine-1-carboxylate (850 mg, 2.25 mmol) in DCM (9 mL) was added at −70° C., and the mixture was stirred at −70° C. for 20 minutes. TEA (1.36 g, 13.44 mmol, 1.87 mL) was added, and the mixture was stirred at −70° C. for 30 minutes. After layer separation, 1 H NMR confirmed the desired product. The mixture was diluted with water (50 mL) and extracted with DCM (20 mL x 2). The combined organic phase was washed with water (20 mL), dried over NaSO, filtered, and concentrated under reduced pressure to give the title compound (860 mg, crude) as a yellow oil. MS (M+H)+ =377.5

[0359] Step 4. Synthesis of tert-butyl 4-(1-(((benzyloxy)carbonyl)amino)-2-(4-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperazin-1-yl)ethyl)piperidine-1-carboxylate (6) To a solution of 3-(3-fluoro-4-(piperazin-1-yl)phenyl)piperidine-2,6-dione (650 mg, 1.98 mmol, HCl) in DCM (10 mL) was added TEA (625.22 mg, 6.18 mmol, 860 μL) and MgSO (716.08 mg, 5.95 mmol), followed by a solution of tert-butyl 4-(1-(((benzyloxy)carbonyl)amino)-2-oxoethyl)piperidine-1-carboxylate (860 mg, 2.28 mmol) in DMF (10 mL), and the mixture was stirred at 25° C. for 15 min. NaBH(OAc) (840.67 mg, 3.97 mmol) was added, and the mixture was stirred at 25° C. for 14 h. LCMS showed 41% of the desired mass. The mixture was combined with another batch (150 mg scale), diluted with water (30 mL), extracted with EtOAc (10 mL x 2), and the combined organic phase was washed with water (10 mL x 2), dried over Na2SO4, and filtered. The filtrate was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (5 g SepaFlash® silica flash column, eluent: 0-10% MeOH / EtOAc gradient @ 50 mL / min) to afford the title compound (720 mg, 994.22 μmol, 50.14% yield, 90% purity) as a yellow solid. MS (M+H) + =652.4

[0360] Step 5. Synthesis of benzyl (2-(4-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperazin-1-yl)-1-(piperidin-4-yl)ethyl)carbamate (7) To a solution of tert-butyl 4-(1-(((benzyloxy)carbonyl)amino)-2-(4-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperazin-1-yl)ethyl)piperidine-1-carboxylate (720 mg, 1.10 mmol) in DCM (5 mL) was added HCl / dioxane (4 M, 10 mL) and the mixture was stirred at 25° C. for 1 h. LCMS showed a peak corresponding to 87% of the desired mass. The mixture was concentrated under reduced pressure to give the title compound (660 mg, crude, HCl) as a yellow solid. MS (M+H) + =552.4

[0361] Step 6. Synthesis of benzyl (2-(4-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperazin-1-yl)-1-(1-nitrosopiperidin-4-yl)ethyl)carbamate (8) To a solution of benzyl (2-(4-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperazin-1-yl)-1-(piperidin-4-yl)ethyl)carbamate (0.3 g, crude, HCl) in THF (6 mL) was added TEA (174.48 mg, 1.72 mmol, 240.00 μL) and t-BuONO (208.08 mg, 2.02 mmol, 240.00 μL), and the mixture was stirred at 60 °C under N for 14 h. LCMS showed a peak corresponding to 50% of the desired mass. The mixture was concentrated under reduced pressure. The residue was purified by flash silica gel chromatography (5 g SepaFlash® silica flash column, eluent: 0-20% EtOAc / petroleum ether gradient @ 50 mL / min) to afford the title compound (0.5 g, 861.11 μmol, 84.40% yield) as a yellow solid. MS (M+H) + =581.4

[0362] Step 7. Synthesis of benzyl (1-(1-aminopiperidin-4-yl)-2-(4-(4-(2,6-dioxypiperidin-3-yl)-2-fluorophenyl)piperazin-1-yl)ethyl)carbamate (9) To a solution of benzyl (2-(4-(4-(2,6-dioxypiperidin-3-yl)-2-fluorophenyl)piperazin-1-yl)-1-(1-nitrosopiperidin-4-yl)ethyl)carbamate (100 mg, 172.22 μmol) and NH4Cl (28.00 mg, 523.45 μmol) in THF (1 mL) and HO (0.3 mL) was slowly added Zn (56 mg, 856.40 μmol), and the mixture was stirred at 25 °C for 1 h. LCMS showed a peak corresponding to 75% of the desired mass. The mixture was combined with another batch (50 mg scale) and then diluted with THF (5 mL). The mixture was filtered, and the filter cake was washed with THF (15 mL). The filtrate was concentrated under reduced pressure to give the title compound (190 mg, crude) as a yellow solid. MS (M+H) + =567.4

[0363] Step 8. Synthesis of benzyl (1-(1-(4-((7,7-difluoro-9-isopropyl-5-methyl-6-oxo-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,4]diazepin-2-yl)amino)-3-methoxybenzamido)piperidin-4-yl)-2-(4-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperazin-1-yl)ethyl)carbamate (11) To a solution of 4-((7,7-difluoro-9-isopropyl-5-methyl-6-oxo-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,4]diazepin-2-yl)amino)-3-methoxybenzoic acid (140 mg, 332.23 μmol) and HATU (151.59 mg, 398.67 μmol) in DMF (1 mL) was added DIPEA (222.60 mg, 1.72 mmol, 0.3 mL) and the mixture was stirred at 25° C. for 15 min. Then, a solution of benzyl (1-(1-aminopiperidin-4-yl)-2-(4-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperazin-1-yl)ethyl)carbamate (190 mg, crude) in DMF (3 mL) was added, and the mixture was stirred at 25 °C for 1 h. LCMS showed a peak corresponding to the desired mass (51%). The mixture was diluted with water (10 mL) and extracted with EtOAc (10 mL x 3). The combined organic phase was washed with brine (10 mL x 3), dried over Na2SO4, filtered, concentrated under reduced pressure, and purified by prep-TLC (EtOAc:MeOH = 10:1) to give the title compound (0.2 g, 173.19 μmol, 52.13% yield, 84% purity) as a yellow solid. MS (M+H) + =970.5

[0364] Step 9. Synthesis of N-(4-(1-amino-2-(4-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperazin-1-yl)ethyl)piperidin-1-yl)-4-((7,7-difluoro-9-isopropyl-5-methyl-6-oxo-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,4]diazepin-2-yl)amino)-3-methoxybenzamide (Compound 31) A solution of benzyl (1-(1-(4-((7,7-difluoro-9-isopropyl-5-methyl-6-oxo-6,7,8,9-tetrahydro-5H-pyrimido[4,5-b][1,4]diazepin-2-yl)amino)-3-methoxybenzamido)piperidin-4-yl)-2-(4-(4-(2,6-dioxopiperidin-3-yl)-2-fluorophenyl)piperazin-1-yl)ethyl)carbamate (170 mg, 147.21 μmol) in TFA (12.28 g, 107.70 mmol, 8 mL) was stirred at 60° C. for 6 hours. The desired mass peak (55%) was detected by LCMS. The mixture was concentrated under reduced pressure and purified by prep-HPLC (column: Phenomenex Luna C18 150 x 25 mm x 10 μm; mobile phase: [water (TFA)-ACN]; gradient: 17%-47% B over 10 min). The eluate was lyophilized to give the title compound (77.4 mg, 59.79 μmol, 40.62% yield, 91% purity, 3% TFA) as a white solid. MS (M+H) + =836.5

[0365] [ka]

[0366] <Experimental Example> 1. PLK1 Luciferase Analysis Generation and culture of HeLa LgBit (PLK1-HiBit KI) cell line A stable LgBit-expressing cell line was created by transfecting a HeLa cell line with the LgBit vector. A gRNA and donor were then constructed to express the HiBit amino acid sequence after the C-terminus of the Plk1 gene present in the cells, and then inserted into the cells along with a CRISPR / Cas9 expression vector. Only cells in which insertion was complete and knock-in had progressed were selected and passaged for use.

[0367] For cell culture, DMEM (Gibco, Cat. No. 11995-065; Lot. No. 2646135), FBS (Gibco, Cat. No. 16000-044; Lot. No. 2634213P), penicillin / streptomycin (PS) (Gibco, Cat. No. 15140-122; Lot. No. 2441887), 100 mm 2 Cell culture dish (SPL, Cat.No.20100), 150mm 2 Cell culture dish (SPL, Cat. No. 20150), 96-well culture plate (SPL, Cat. No. 30196), PBS pH7.4 (Gibco, Cat. No. 10010-023; Lot. No. 2509235), TrypLE TM Express (Gibco, Cat. No. 12605-010; Lot. No. 2323417), counting chamber (hematocytometer) (together, Cat. No. 4-458-01), and 0.4% trypan blue solution (DYNEBIO, Cat. No. CBT3710; Lot. No. 20221111) were used.

[0368] Luciferase analysis The example compounds were used in the experiments after being completely dissolved in DMSO (Sigma-Aldrich Cat. No. D2438, Lot. No. RNBL5438).

[0369] For HeLa LgBit (Plk1-HiBit KI), thymidine block was followed by release and subsequent compound treatment. The procedure was as follows: Thymidine (Sigma-Aldrich Cat. No. T9250-5G) was completely dissolved in DW before use. For thymidine block, 2 mM thymidine was added and the cells were incubated for 24 hours. For release and chemical treatment, the medium was suctioned and then washed with 1x PBS. TrypLE™ was added and the cells were incubated for 5 minutes in a 37°C CO2 incubator (Thermo Fisher Science, Cat. No. 4111). Complete medium was added, and the cells were neutralized and counted using a counter. 3.3x10 cells were added to each well of a 96-well culture plate (SPL). 4 After seeding, the total volume of the medium was 150 μL and the cells were incubated in a CO2 incubator.

[0370] After incubating each cell line in a CO2 incubator for 18 hours, Endurazine (Promega, Cat. No. N257B) was added to each well to make 4% of the total volume. The compounds of the present invention were placed in a 96-well white plate (SPL) at a concentration of 300 nM. The wavelength of the plate reader (BMG Labtech, CLARIOstar Plus) was set to 470-480 nM, and the absorbance was measured in real time. After 9 hours, the luminescence values ​​were measured and displayed as bar graphs using an Excel program.

[0371] The results are shown in the table below.

[0372] [Table 3] [Table 3]

[0373] 2. Cell viability analysis in NCI-H69 and NCI-H526 cell lines Cultivation of NCI-H69 and NCI-H526 cell lines NCI-H69 (hereafter H69) and NCI-H526 (hereafter H526) cell lines were purchased from the Korea Cell Line Bank (KCLB, Seoul, Republic of Korea). For cell culture, RPMI 1640 (Gibco, Cat. No. 22400-089; Lot. No. 2537146), FBS (Gibco, Cat. No. 16000-044; Lot. No. 2511328P), penicillin / streptomycin (PS) (Gibco, Cat. No. 15140-122; Lot. No. 2441887), 75T cell culture flasks (SPL, Cat. No. 71075), 175T cell culture flasks (SPL, Cat. No. 71175), 96-well culture plates (SPL, Cat. No. 30096), PBS pH 7.4 (Gibco, Cat. No. 10010-023; Lot. No. 2509235), TrypLE TM Express (Gibco, Cat. No. 12605-010; Lot. No. 2323417), counting chamber (hematocytometer) (As one, Cat. No. 4-458-01), and 0.4% trypan blue solution (DYNEBIO, Cat. No. CBT3710; Lot. No. 20221111) were used.

[0374] Cell viability analysis The example compounds were used in the experiments after being completely dissolved in DMSO (Sigma-Aldrich Cat. No. D2438, Lot. No. RNBL7287). H526 cells were cultured in a 96-well culture plate (SPL) at 3 x 10 cells per well. 4The cells were seeded in a volume of 150 μL, and the medium volume in each well was adjusted to 150 μL. The intracellular treatment volume of the compound of the present invention was adjusted to a maximum concentration of 3000 nM, which was then diluted 1 / 3 to achieve a minimum concentration of 0.46 nM. Each well was treated with the compound to a total solution volume of 200 μL and then cultured in a CO2 incubator (Thermo Fisher Science, Cat. No. 4111) for 5 days. Then, each well was treated with 20 μL of EZ-Cytox (DOGEN, Cat. No. EZ-3000, Lot. No. DLS2308) and cultured in a CO2 incubator for 4 hours. After incubation, the absorbance of the sample was measured using a plate reader (BMG Labtech, CLARIOstar Plus) at 450 nM wavelength. The sample was stirred in the plate reader for 3 minutes before measurement. The final measurements were organized in an Excel file, and then graphed using the Prism-GraphPad program. 50 The values ​​were measured.

[0375] The results of cell viability analysis for H69 and H526 cell lines are shown in Tables 4 and 5 below (A: IC 50 <20nM, B:IC 50 50nM or less, C:IC 50 100nM or less).

[0376] [Table 4] [Table 4]

[0377] [Table 5] [Table 5]

Claims

1. A compound represented by the following formula I: [Chemical formula I] 【Chemistry 1】 In the above formula, L １ is a covalent bond or -(X ５ ) １～３ - and {where X ５ Is, L １ each independently represents -CH, provided that -NH- is absent or present at most one time within ２ - or -NH-}; L ２ is a covalent bond or -(X ６ ) １～３ - and {where X ６ Is, L ２ -C(O)-, -NH-, -N(CH ３ )- and -CH(NH ２ )— is independently absent or present at most 1 time, and each independently represents —CH ２ -, -C(O)-, -NH- or -CH(NH ２ ) - is}; L ３ teeth, 【Chemistry 2】 or 【Transformation 3】 where L ３ teeth, 【Chemistry 4】 Through X ４ covalently bonded to X １ , X ２ , X ３ and X ４ are each independently CH or N; X ７ and X ８ａ are each independently a covalent bond or —CH ２ - and; X ８ｂ is -H or -CH ３ and R １ is -OCH ３ or -OCF ３ and ULM is a moiety represented by the following chemical formula II-1, II-2, or II-3: [Chemical formula II-1] 【Transformation 5】 [Chemical formula II-2] 【Transformation 6】 [Chemical formula II-3] 【Transformation 7】 In the above formula, Ring U is phenyl or a 5- or 6-membered heteroaryl; U １ is -NH-, -NHCH ２ --NHCH ２ CH ２ -, -CH ２ NH-, -CH ２ CH ２ NH—, —NHCO—, —CONH—, or —O—; U ２ is CH ２ or C(O); R Ｕ is a halo.

2. The compound according to claim 1, wherein the chemical formula I is the following chemical formula I-1: [Chemical formula I-1] 【Transformation 8】 In the above formula, L １ａ is -CH ２ -, -NH-, -CH ２ CH ２ --NHCH ２ -, -CH ２ NH-, -CH ２ CH ２ CH ２ --NHCH ２ CH ２ -, -CH ２ NHCH ２ - or -CH ２ CH ２ It is NH-.

3. The compound according to claim 1, wherein the chemical formula I is the following chemical formula I-2: [Chemical formula I-2] 【Chemistry 9】 In the above formula, X ９ is -CH ２ - or -CH(NH ２ )-.

4. The compound according to claim 1, wherein the chemical formula I is the following chemical formula I-3: [Chemical formula I-3] 【Chemistry 10】 In the above formula, X １０ represents a covalent bond, —NH— or —CH(NH ２ )- and; X １１ is a covalent bond or -CH ２ - is.

5. The compound according to claim 1, wherein chemical formula I is represented by the following chemical formula I-4: [Chemical formula I-4] 【Chemistry 11】 In the above formula, L １ｂ is a covalent bond or -CH ２ NH-; L ２ｂ is a covalent bond, -CH ２ NH-, -CH ２ N (CH ３ )- or -CH ２ CH(NH ２ )C(O)—; X ８ａ is a covalent bond or -CH ２ - and; X ８ｂ is -H or -CH ３ is.

6. The compound of claim 1 selected from the group consisting of compounds 1-25. Table 1-1 Table 1-2 Table 1-3 Table 1-4 Table 1-5

7. A compound represented by the following formula III: [Chemical formula III] 【Chemistry 12】 In the above formula, L ２ は、-CH ２ -、-NHCH ２ -、-CH ２ NH-、-CH(NH ２ )CH ２ -、-CH ２ CH(NH ２ )-、-C(O)CH ２ CH ２ -または-CH ２ CH ２ C(O)-; X １ , X ２ , X ３ and X ４ are each independently CH or N; X ７ is a covalent bond or -CH ２ -; R ２ａ and R ２ｂ is halo; or R ２ａ and R ２ｂ are linked together to form a 3- to 6-membered ring; R ３ is -C １－３ alkyl or 3- to 7-membered cycloalkyl; ULM is a moiety represented by the following chemical formula II-4: [Chemical formula II-4] 【Chemistry 13】 In the above formula, U ３ is a covalent bond or —NH—; R Ｕ is a halo.

8. The compound of claim 7 selected from the group consisting of compounds 26-31. Table 2-1 Table 2-2

9. 9. A compound according to any one of claims 1 to 8 which induces polo-like kinase 1 (PLK1) proteolysis.

10. 10. A pharmaceutical composition comprising a compound according to any one of claims 1 to 9 and at least one pharmaceutically acceptable carrier.

11. 10. A pharmaceutical composition comprising a compound according to any one of claims 1 to 9, wherein the compound is conjugated to an antibody or an antigen-binding fragment thereof via a linker.

12. A pharmaceutical composition for treating cancer, benign tumors or neurological disorders, comprising a compound according to any one of claims 1 to 9.

13. 10. An antibody-drug conjugate comprising: an antibody or an antigen-binding fragment thereof; and a compound according to any one of claims 1 to 9, wherein the compound is conjugated to the antibody or antigen-binding fragment thereof via a linker.

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