Efficient synthesis of β-L-5-[(E)-2-bromovinyl)-1-((2S,4S)-2-(hydroxymethyl)-1,3-(dioxolan-4-yl)uracil)] (L-BHDU) via chiral pure L-dioxolane

Abstract

The present invention relates to a novel process for the synthesis of L-BDHU from (7R)-2,2-dimethyl-1,3-dioxolane-4-carboxylate (7) in as few as 7 steps, as well as related starting materials and intermediate compounds. The present invention eliminates the need for chiral purification of the expensive L-dioxolane (11), resulting in enantiomerically enriched (ee > 99%) compounds. The optically pure compound 11 is utilized to construct L-BHDU (15) and its monophosphate prodrug (POM-L-BHDU, 22). The novel synthetic process and novel intermediate compounds represent additional embodiments of the present invention.

Description

Technical Field

[0001] This invention relates to a novel method for synthesizing L-BDHU, along with related starting materials and intermediate compounds, from (R)-2,2-dimethyl-1,3-dioxolane-4-carboxylate (7) in as few as seven steps. The invention eliminates the costly chiral purification of L-dioxolane (11), resulting in enantiomeric enriched compounds (ee > 99%). L-BHDU (15) and its monophosphate prodrug (POM-L-BHDU, 22) were constructed using optically pure compound 11. The novel synthetic method and novel intermediate compounds represent further embodiments of the invention.

[0002] Related applications

[0003] This application claims the priority of U.S. Provisional Application Serial No. US63 / 621,722, filed January 17, 2024, and US63 / 716,343, filed November 5, 2024, the entire contents of each of which are incorporated herein by reference.

[0004] Background Technology and Invention Overview

[0005] Varicella-zoster virus (VZV) is a highly contagious alpha herpesvirus that causes chickenpox (varicella) upon initial infection and herpes zoster (shingles) upon reactivation from the incubation period. 1 The U.S. Centers for Disease Control and Prevention (CDC) estimates that there are approximately one million cases of shingles each year in the United States. 2 People over 50 years of age, those with weakened immune systems, HIV-infected individuals, and organ transplant recipients have a higher risk of VZV infection. 3 VZV infection can trigger significant complications, resulting in a painful, vesicular skin rash containing a large amount of the infectious virus. A notable problem with shingles is postherpetic neuralgia, a persistent pain that can last for months or years even after the rash has healed. 4 Therefore, there is a need for effective and safe new antiviral drugs for the treatment and management of VZV infection. However, while vaccination can be used for both stages of VZV infection, and adjuvanted subunit vaccines have been approved for the prevention of shingles, these are only suitable for healthy individuals. 5

[0006] Acyclovir (ACV), valacyclovir (VACV), and famciclovir (FCV) Figure 1 ( ) is an approved drug and is being used to treat VZV infection. 6However, these approved drugs are not highly effective against VZV and require high doses and long-term use, which often increases resistance. 7 Sidofovir (CDV) is a broad-spectrum antiviral drug that is active against VZV, but it is associated with nephrotoxicity and lacks an oral administration route. 6 Another antiviral drug, brivudine (BVDU), has been approved in Europe for the treatment of VZV infection. 8, 9 One major drawback associated with BVDU is that it is metabolized in the liver to bromovinyluracil (BVU). 8 Bvrukine (BVU) inhibits the activity of dihydropyrimidine dehydrogenase (DPD), an enzyme that breaks down thymidine and uracil. Therefore, the combined use of brivudine with 5-fluorouracil (5-FU) in cancer patients carries a life-threatening risk. 10 Due to the significant adverse reactions of currently approved drugs, there is an urgent need for new antiviral drugs to treat VZV and its drug-resistant strains.

[0007] For the past two decades, in order to find better antiviral compounds against VZV, herpes simplex virus types 1 and 2, and Epstein-Barr virus (EBV), the inventors' research team has been dedicated to discovering modified D and L-dioxolane nucleotides (acids). In these efforts, the inventors have invented 2-(hydroxymethyl)-1,3-dioxolane-4-yl]5-vinyluracil. 11 Pyridine (L-HDVD, Figure 2 ), 2-bromovinyl-2-( 12, 13 L-BHDU (1,3-dioxolane- ... 50 The value was 0.01 μM) and Kaposi's sarcoma-associated herpesvirus (KSHV) (EC) 50 = 0.09 μM) has high activity. 11 L-BHDU has been shown to have an EC50 concentration of 0.25 μM. 50 The value was high, while no cytotoxicity was observed at concentrations up to 200 μM in human foreskin fibroblasts (HFF), with a selectivity index (SI) > 909. 12 In in vivo studies, L-BHDU significantly reduced viral load compared to ACV and VCV. Notably, metabolic studies revealed that L-BHDU does not inhibit DPD and exhibits better safety and antiviral properties than brivudine. 12

[0008] Recently, in order to improve the cellular bioavailability and uptake of L-BHDU and enhance its pharmacokinetic properties, the inventors have developed a prodrug of L-BHDU monophosphate neopentyloxymethyl ester (POM-L-BHDU-MP). Figure 2 ). 14, 15 POM-L-BHDU-MP has shown similar antiviral activity to L-BHDU in infected cells. In contrast, POM-L-BHDU-MP is superior to L-BHDU in the VZV mouse model. 16 Pharmacokinetic (PK) studies have shown that POM-L-BHDU-MP has better oral absorption compared to L-BHDU. 14 Recent pharmacokinetic (PK) studies have also shown that POM-L-BHDU-MP, whether administered intravenously or orally, releases nearly equivalent concentrations of L-BHDU in the bloodstream. This demonstrates that oral administration of POM-L-BHDU-MP is as effective as intravenous administration. Repeated studies in humanized mice have shown that POM-L-BHDU-MP is effective when administered orally once daily at doses of 11.3 mg / kg and higher, indicating its potency and bioavailability in vivo. 16 POM-L-BHDU-MP was evaluated as a topical treatment for VZV and HSV infections in a human skin explant model, and was highly effective against both viruses when formulated at a 0.2% concentration in cocoa butter. 16 Based on these findings, POM-L-BHDU-MP was selected for preclinical development targeting VZV and HSV-1 infections.

[0009] To develop POM-L-BHDU-MP into a preclinical candidate, further expanded biological, pharmacokinetic, and toxicological studies are needed, requiring a large quantity of POM-L-BHDU-MP. Therefore, a stable, practical, and cost-effective synthetic method for POM-L-BHDU-MP is needed. Early synthesis of L-BHDU via the key intermediate L-dioxolane (… Figure 3 Option 1) was used. The method reported by Sznaidman et al. was employed. 17, 18 It is used in the synthesis of L-dioxane-5, which is a key intermediate in the synthesis of L-modified nucleoside analogs.

[0010] Scheme 1. Chiral pure D- and L-dioxolane were synthesized by chiral separation of racemic dioxolane (4). 17

[0011]

[0012] Reagents and conditions: (a) DMAP, Et3N, tert-butyl methyl ether, room temperature; (b) BF3, Et2O, acetonitrile, 0°C to room temperature.

[0013] However, the reported method involves the chiral chromatographic separation of racemic dioxolane (4), which limits the scalability and commercial application of Scheme 1. Furthermore, during large-scale synthesis, the decomposition of intermediate 4 was observed in the presence of excess boron trifluoride diethyl ether (BF3.Et2O). Chiral pure D- and L-dioxolane (5 and 6) also exhibited stability issues during chiral separation, and the collected chiral pure fractions formed undesirable impurities upon concentration or lyophilization. These shortcomings of Scheme 1 limit the methods for the large-scale synthesis of L- and D-dioxolane (5 and 6). To overcome the challenges of Scheme 1, the inventors here report a scalable and practical synthesis of L-BHDU from (R)-2,2-dimethyl-1,3-dioxolane-4-carboxylic acid methyl ester 7 in seven steps. However, the method reported herein is an improved method, particularly for the synthesis of L-dioxolane, which was previously reported by Bera S. et al. Previous reports 19 The methods and patents contain many unclear information and require medicinal chemists to synthesize chiral pure L-dioxolane (enantiomer excess ≥ 99%). 20 However, this application relates to a method for the direct synthesis and purification of chiral pure L-dioxolane via diastereomeric chiral amine salt formation. This novel method also eliminates chiral separation and certain column chromatography steps, making it suitable for the scalable synthesis of POM-L-BHDU-MP for clinical and commercial applications. Attached Figure Description

[0014] Figure 1 The chemical structures of several antiviral drugs used to treat VZV infection are shown.

[0015] Figure 2 The chemical structures of L-HDVD, L-BHDU, and POM-L-BHDU-MP are shown.

[0016] Figure 3 Scheme 1 demonstrates the chemical synthesis of chiral pure D- and L-dioxolane via chiral separation of racemic dioxolane (4). 17 Reagents and conditions: (a) DMAP, Et3N, tert-butyl methyl ether, room temperature; (b) BF 3∙ ET2O, acetonitrile, 0°C to room temperature.

[0017] Figure 4Scheme 2 demonstrates the synthesis of L-BHDU via the chiral pure key intermediate L-dioxolane (11). Reagents and conditions: (a) p-TSA, or Dowex 50W X8 toluene, 80°C; (b) 1 M LiOH aqueous solution, THF, 0°C to room temperature; (c) i) (S)-phenylethylamine, acetonitrile, 75°C to room temperature; BF3.Et2O, acetonitrile, 0°C to room temperature; (ii) EtOAc:IPA (3:1), room temperature; (d) 1 N HCl aqueous solution, room temperature; (e) manganese diacetate (Mn(II)(OAc)2), diacetoxyiodobenzene, acetic acid, 2-Me-THF 65°C, or alternatively Pb(OAc)4, pyridine, acetonitrile, 0°C to room temperature; (f) bromovinyluracil, TBDMSOTf, TMSI, DCM, room temperature; (g) BCl3, DCM, -78°C.

[0018] Figure 5 The ORTEP diagram of (a) compound 10 confirms the relative stereochemistry of the L-dioxolane. (b) shows the stereostructures of the D- and L-dioxolane; in the case of the D-dioxolane, the C-2 and C-4 hydrogens are cis, while in the case of the L-dioxolane, the C-2 and C-4 hydrogen atoms are trans to each other.

[0019] Figure 6 Scheme 3 illustrates an improved synthesis of L-BHDU from L-dioxolane 11 via intermediate 18. Reagents and conditions: (a) 5% Pd / C, H2 gas, MeOH, room temperature; (b) isobutyric anhydride, pyridine, DMAP, DCM, 0°C to room temperature; (c) Mn(OAc)2, diacetoxyiodobenzene, acetic acid, 2-Me-THF, 65°C, or alternatively Pb(OAc)4, pyridine, acetonitrile, 0°C to room temperature; (d) bromovinyluracil, TBDMSOTf, TMSI, DCM, room temperature; (e) 7 N NH3 in methanol, room temperature.

[0020] Figure 7 Scheme 4 illustrates the synthesis of POM-L-BHDU-MP prodrug via L-BHDU (15). Reagents and conditions: (a) NMI, THF, 0°C to room temperature, 3 hours. Summary of the Invention

[0021] In embodiments, the present invention relates to a method for synthesizing L-BDHU (15) via chemical precursors and chemical intermediates, resulting in

[0022] L-BHDU (15), POM-L-BHDU-MP (22), and the efficient synthesis of many precursors and / or chemical intermediates for the synthesis of these compounds.

[0023] In an embodiment, the present invention relates to a method according to the appended Figure 4 The synthetic steps described in Scheme 2 are a method for synthesizing L-BDHU (15) from compound (7). First, compound 7 is converted into the pure key intermediate L-dioxolane (11) in four steps, and then L-dioxolane 11 is converted into L-BHDU (15) via one of the two synthetic routes disclosed below. According to the method of the first embodiment, methyl-(R-)-2,2-dimethyl-1,3-dioxolane-4-carboxylate (compound 7) is used to prepare L-dioxolane compound 11 by first reacting it with 2-(benzyloxy)acetaldehyde in a solvent (preferably toluene) at a catalytic amount of acid (preferably toluene / p-toluenesulfonic acid or Dowex 50W X8) at a high temperature (above room temperature, e.g., 60°C to 100°C for several hours) to obtain a diastereomeric mixture (typically 1:1) of benzyl-protected dioxolane ester compound 8 in high yield (typically >70%), as shown below. Compound 8 is then subjected to ester hydrolysis in an aqueous solvent / base (e.g., 1 M LiOH / THF) to remove the ester group, yielding the corresponding benzyl-protected carboxylic acid ester compound 9, typically in yields greater than 90%. Compound 9 is then complexed with (S)-phenylethylamine via the formation of an acid-base salt to give substantially pure (i.e., de) > 90%, usually > Compound 10 (99%) was obtained by first reacting a benzyl-protected racemic carboxylic acid ester compound 9 with (S)-phenylethylamine in a solvent (e.g., acetonitrile, preferably at a high temperature of 70°C for about 2 hours, then cooling to room temperature and reacting for another 2 hours), to yield a salt of compound 10 containing a mixture of both D and L isomers (15% D, 85% L, de). > 70%, referred to as compound mixture 10M), is precipitated and / or crystallized to obtain a salt mixture of the D and L isomers of acid amine 10 (referred to as compound 10M), which is then dissolved (preferably several times) in a 3:1 volume ratio of ethyl acetate:isopropanol, stirred at room temperature for several hours (e.g., 3, 4, or 5 hours, typically 4 hours) and precipitated. The mixture is extracted 2 to 5 times, typically 3 to 5 times, and in preferred embodiments typically 3 times, to obtain substantially pure (de) > 90%, usually > (99%) (S)-phenylethylamine salt (acidic amine salt) 10. Then, (S)-phenylethylamine salt 10 was dissolved in dichloromethane (DCM) and exposed / subsequently washed with cold aqueous acid (e.g., 1 N HCl aqueous solution), brine, and dried (e.g., sodium sulfate) to give compound 11 (L-dioxolane), which is diastereomeric or substantially diastereomeric (de) > 90%, de>95%, usually >(99%, most commonly 99+% to 100%). Therefore, high purity compound 11 (as trans / L form) is obtained from compound 9 by precipitation without chromatographic separation. It should be noted that one or more of the above steps are carried out in separate steps or in a single-pot reaction vessel.

[0024]

[0025] In the embodiments, compound 11 is converted into compound 15 via compounds 12 and 13, as described below and in the appendix. Figure 4 As described in Scheme 2. In this embodiment, compound 11 is first reacted with Mn(II)OAc, diacetoxyiodobenzene, and acetic acid in 2-Me-THF at 65°C (or alternatively, reacted with lead tetraacetate Pb(OAc)4 in acetonitrile / base (usually pyridine or trimethylamine, more usually pyridine), the components are combined at 0°C, and then reacted at room temperature for 16 hours, a step not shown in the following scheme), and chromatographic separation is performed (preferably column chromatography, eluted with ethyl acetate / hexane) to obtain a mixture of α and β anomers of benzyl-protected dioxolane acetate compound 12 (α / β ratio typically about 2:1). In a dry solvent (e.g., dichloromethane (DCM)), compound 12 (as a mixture of α and β isomers) was coupled to bromovinyluracil using tert-butyldimethylsilyl trifluoromethanesulfonate (TBDMSOTf), trimethyliodosilane (TMSI), and 2,4,6-trimethylpyridine, followed by chromatography (e.g., silica gel column, 1:4 EtOAc / hexane as eluent) to give minor fractions of α-isomer compound 14 (yield approximately 10% to 20%, undesirable) and the desired β-isomer compound 13 (yield approximately 10% to 20%). > 50%, typically 55% or higher). Compound 13 is then deprotected of the benzyl group (e.g., in DCM, using BCl3, at low temperatures, e.g., -78°C) to... > Compound 15 was obtained in 50% yield. Each of the above synthetic steps can be carried out in a separate step or together in a single reaction vessel.

[0026]

[0027] In the embodiments, the present invention relates to a method for synthesizing compound 15 from L-dioxolane acid 11 via compounds 16 to 20, as described below and appended. Figure 6As described in Scheme 3. In this embodiment of the invention, compound 11 is benzyl deprotected (preferably by reductive cleavage, typically with Pd / C, hydrogen, in MeOH, at room temperature) to give unprotected dioxolanic acid compound 16 in high yield, followed by protection of its free hydroxyl group with an isobutyrate group. This step is, for example, by reacting compound 16 with isobutyric anhydride in a base (e.g., pyridine and dimethylaminopyridine (DMAP)) in a dichloromethane solvent, initially at 0°C, followed by a reaction at room temperature (e.g., overnight, 12 to 20 hours, typically 16 hours) to give isobutyrate-protected compound 17, typically in yield greater than 80% to 85%. Compound 17 is acylated in 2-Me-THF using Mn(II)OAc, diacetoxyiodobenzene, and acetic acid to form compound 18 as a diastereomeric mixture (e.g., initially at 0°C, followed by overnight or 12 to 20 hours at room temperature, typically 16 hours, then continued at 65°C for 4 hours). Alternatively, lead tetraacetate (Pb(OAc)4) can be used to combine the components at 0 °C in acetonitrile / base (typically pyridine or trimethylamine, more typically pyridine), followed by a reaction at room temperature for 16 hours (alternative steps are not shown in the following schemes). Compound 18 is then coupled to bromovinyluracil in dichloromethane (DCM) using tert-butyldimethylsilyltrifluoromethanesulfonate (TBDMSOTf), trimethyliodosilane (TMSI), and 2,4,6-trimethylpyridine to give a diastereomeric mixture of compounds 19 and 20, which is then subjected to chromatography (e.g., silica gel, using 15% to 18% EtOAc / hexane) to give compound 20, typically in a yield greater than about 45% to 50%, which can be readily converted to L-BHDU (15) by exposure to a base in a solvent (e.g., NH3 / MeOH). Each of the above synthetic steps can be carried out in a separate step or together in a single reaction vessel.

[0028]

[0029] In this embodiment, the invention relates to the synthesis of benzyl-protected dioxolaric acid 11 from benzyl-protected dioxolaric acid 9 by reacting (S)-phenylethylamine with compound 9 in acetonitrile at room temperature for several hours (e.g., typically about 4 hours) to form a mixture of D and L isomers of benzyl-protected phenylethylammonium salt 10 (the mixture of isomers is also referred to as 10M). The solid mixture is then resuspended in ethyl acetate / isopropanol at a 3:1 ratio (by volume) for 4 hours and filtered. This resuspension process is optionally and preferably repeated several times until the undesirable D isomer is removed from the salt mixture, yielding substantially pure L-isomer compound 10 (de is at least 90%, typically at least 95%, at least 99%, 99+%, 99.3+%). The L-isomer (compound 10) is then exposed to an aqueous acid (e.g., 1N aqueous HCl) at room temperature for a sufficient duration to yield benzyl-protected L-dioxolaric acid 11. Compound 11 can be readily converted into deprotected L-dioxolane 16 by removing the benzyl protecting group under reducing conditions (e.g., Pd / C, H2).

[0030]

[0031] In the embodiments, the present invention relates to a method for synthesizing isobutyrate-protected nucleoside compound 20 from L-dioxolane 17 protected by isobutyrate, wherein compound 17 is acylated by using Mn(II)OAc, diacetoxyiodobenzene, acetic acid in 2-Me-THF (or alternatively, lead tetraacetate Pb(OAc)4 in acetonitrile / base (usually pyridine or trimethylamine, more usually pyridine), the components are combined at 0°C, and then reacted at room temperature for 16 hours, not shown in the following scheme) to form a diastereomeric mixture of acylated protected L-dioxolane compound 18. Compound 18 is then coupled with bromovinyluracil in dichloromethane (DCM) using tert-butyldimethylsilyltrifluoromethanesulfonate (TBDMSOTf), followed by trimethyliodosilane (TMSI), to give a diastereomeric mixture of compounds 19 and 20. The diastereomeric mixture of compounds 19 and 20 is subjected to column chromatography to give compound 20. Compound 20 was then exposed to ammonia / methanol (or other suitable base) to remove the isobutyrate protecting group, yielding the final compound L-BHDU 15. Each of the above synthetic steps can be performed in a separate step or together in a single reaction vessel.

[0032]

[0033] In an embodiment, such as Figure 7As shown in Scheme 4, L-BHDU (15) is converted to POM-L-BHDU-MP (22) by reacting compound 15 with bis(POM)phosphoryl chloride (21) in a THF solvent in the presence of a weak base (e.g., N-methylimidazole, NMI), and then purified (e.g., by chromatography) and crystallized to obtain compound 22 in a yield greater than 40%.

[0034] In the embodiments, the invention also relates to any one or more compounds, including the aforementioned intermediate compounds, or salts thereof, including pharmaceutically acceptable salts.

[0035] These and / or other embodiments of the invention can be readily obtained from the presentation of the specification and the subsequent determined discussion and review of examples. Detailed Implementation

[0036] The following terms are used to describe this invention. Where a term is not defined, it is given its commonly accepted meaning in the art. According to this invention, conventional chemical synthesis methods and other biological and pharmaceutical techniques within the scope of the art can be employed. Such techniques are well known and are further fully explained in the literature.

[0037] Where a range of values ​​is provided, it should be understood that each intermediate value between the upper and lower limits of the range, up to one-tenth of the unit of the lower limit, unless the context explicitly states otherwise (such as in the case of a group containing multiple carbon atoms, in which case the number of each carbon atom falling into the range is provided), and any other stated or intermediate values ​​within the range, are covered within the invention. The upper and lower limits of these smaller ranges may be independently included within that smaller range and also covered within the invention, subject to any explicitly excluded limits within the stated range. Where the range contains one or two limits, the invention also includes ranges excluding any two of those included limits.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. While any methods and materials similar to or equivalent to those described herein may also be used in the practice or testing of this invention, preferred methods and materials are described hereafter. It should be noted that, unless the context clearly indicates otherwise, the singular forms “a,” “and,” and “the” as used herein and in the appended claims include plural referents. When the term “about” is used, it indicates the quantity or number specifically stated. + Amount within 5%.

[0039] Unless otherwise stated, the term "compound" as used herein refers to any specific chemical compound or intermediate disclosed herein, and generally refers to β-L nucleoside analogs or D and L dioxolane intermediates used to produce these nucleoside compounds using the synthetic steps described herein, but in the context may include tautomers, regioisomers, geometric isomers, angiomers, and, where applicable, their optical isomers (enantiomers) or generally diastereomers (two or more chiral centers), as well as their pharmaceutically acceptable salts, their solvates, and / or polymorphs. In its use in the context, the term "compound" generally refers to a single compound, but may also include other compounds such as stereoisomers, regioisomers, and / or optical isomers (including racemic mixtures and / or diastereomers as described herein), as well as specific enantiomers, enantiomer-enriched or single diastereomers, or mixtures of these disclosed compounds. It should be noted that if a carbon range is provided for a compound, the range indicates that each carbon is individually considered part of that range. For example, C1-C 20 Group descriptions include groups having a single carbon atom, two carbon atoms, three carbon atoms, four carbon atoms, or up to twenty carbon atoms.

[0040] The term "salt" or "pharmaceutically acceptable salt" is used throughout this specification to describe the salt form of one or more compounds described herein, which, where applicable, are provided to increase the yield of synthetic reactions, or alternatively, in some administered embodiments, to increase the solubility of the compound in gastric juices of a patient's gastrointestinal tract to promote the solubility and bioavailability of the compound. Pharmaceutically acceptable salts include, where applicable, salts derived from pharmaceutically acceptable inorganic or organic bases and acids. Suitable salts comprise salts of alkali metals such as potassium and sodium, and alkaline earth metals such as calcium, magnesium, and ammonium salts, among many other acids well known in the pharmaceutical field. In relevant cases, sodium and potassium salts are particularly preferred as neutralizing salts of phosphates according to the invention.

[0041] The term “pharmaceuticalally acceptable derivative” is used throughout the specification to describe any pharmaceutically acceptable prodrug form (such as ester, ether or amide, aminophosphate, phosphate, phosphonate or other prodrug group) that, when administered to a patient, directly or indirectly provides the compound of the invention or an active metabolite of the compound of the invention.

[0042] As used in the context of this invention, the term "D-configuration" refers to the configuration of the nucleoside compounds and other intermediates according to the invention, which mimics the native configuration of the sugar moiety, as opposed to the non-naturally occurring nucleosides or "L" configurations, which describe most compounds used in chemical synthesis or as the final products described herein. The term "β" or "β-angiomata" is used to describe intermediates or nucleoside analogs according to the invention, wherein the nucleoside base is configured (set) above the plane of the dioxolane moiety in the compound.

[0043] The terms “diastere excess,” “de,” or “enantiomer excess,” and “ee” are used throughout the specification to describe an intermediate compound or nucleoside compound in which a single diastereomer or a single enantiomer is in excess of at least about 90%, typically at least about 95%, preferably at least about 96%, more preferably at least about 97%, even more preferably at least about 98%, and even more preferably at least about 100% or more. According to the invention, dioxolane nucleoside compounds such as L-BHDU or derivatives thereof are generally analogs of β-L-nucleoside compounds. When compounds according to the invention are mentioned in this specification, unless otherwise stated, it is assumed that the intermediate or final nucleoside compound has an L-nucleoside configuration and is diastereomerically and / or enantiomerically enriched (preferably about 100% L-nucleoside). The terms “diastereisopure,” “diastereisorich,” “diastereisoexcess,” or “de” are used to describe a single diastereomer of a compound according to the invention, which contains an excess of at least 90 wt%, 95 wt%, 96 wt%, 97 wt%, 98 wt%, 99 wt%, 99+ wt%, 99.5 wt%, or 100 wt% of the diastereomer, excluding other possible diastereomers.

[0044] The term "stereoselectivity" is used to describe a synthetic step or series of steps in which a single reactant produces a specific isomer, enantiomer, or diastereomer (at least two possible isomers or diastereomers) in greater quantities than one or more possible isomers or diastereomers derived from that reactant. In some cases, the stereoselectivity of the reaction can approach 100%.

[0045] The terms "protecting group" or "blocking group" are used to describe chemical groups or portions introduced into a molecule through chemical modification of a functional group to achieve chemoselectivity and / or stereoselectivity in subsequent chemical reactions. Protecting / blocking groups play an important role in providing precursors of chemical components that provide compounds according to the invention. Blocking groups are typically used to protect hydroxyl groups on intermediates to form compounds according to the invention. In the present invention, typical blocking groups are generally used on alcohol or phosphate groups and primarily include benzyl groups (removed by hydrogenolysis), isobutyrate groups (removed by base), methyl ester groups (removed by base), acetyl groups (removed in coupling reactions), and neopentanoyl methyl ester (POM) groups on phosphate ester intermediates. Neopentanoyl methyl ester (POM) groups are also used on phosphate groups in the final compound POM-L-BHDU-MP to infuse the nucleoside compound with prodrug characteristics to enhance bioavailability. These and other / or groups are described herein.

[0046] Overview and Results of Chemical Synthesis

[0047] The extensive efforts by various research teams to construct chiral pure L-dioxolane typically result in a racemic mixture of D and L-dioxolane, requiring expensive chiral SFC purification to obtain chiral pure D and L-dioxolane. To remove chiral SFC separation, Bera S. et al. 19 The synthesis of chiral dioxolane via methyl-(R)-2,2-dimethyl-1,3-dioxacyclopentane-4-carboxylate has been reported. However, the reported procedure is ambiguous and requires rigorous analytical techniques to confirm the D and L stereoisomers, which can sometimes occur at the end of the final undesirable conformation. In this example, the inventors obtained a real sample of L-BHDU that matched that synthesized via the reported procedure by Bera S. et al. Subsequently, the inventors found that, without real samples and chiral HPLC, the procedure proved very challenging for providing the desired isomers of the target compound. To achieve the scalable synthesis of L-BHDU, a new scheme for synthesizing specific chiral pure L-dioxolane was urgently needed, leading to the research that resulted in this invention. This invention focuses primarily on the synthesis of chiral L-dioxolane with excellent enantiomeric excess (ee ≥ 99%). It is worth noting that this procedure is applicable to the large-scale synthesis of L-derived dioxolane nucleotides, such as troxacitabine. 21 It can also accelerate the study of extended structure-activity relationships (SARs) of therapeutically significant D- and L-dioxane derivatives.

[0048] The synthesis of the key intermediate of chiral pure L-dioxolane (11) was initiated by trans-ketalization condensation of commercially available (R)-2,2-dimethyl-1,3-dioxolane-4-carboxylate (7) with 2-benzyloxyacetaldehyde in the presence of p-TSA, yielding a racemic 1,3-dioxolane derivative in a 1:1 diastereomeric mixture of dioxolane esters 8 in 72% yield. Figure 4 (Scheme 2). Next, the methyl ester (8) was hydrolyzed in 1 M LiOH aqueous solution in THF to give a diastereomeric mixture of acids (9) in 92% yield.

[0049] The goal thereafter was to obtain pure L-dioxolane (11) with high enantiomeric purity (ee > 99%) by avoiding the chromatographic separation of racemic acid (9). However, the selective separation of L-dioxolane is also challenging. One approach is to insert a chiral auxiliary via esterification of p-hydroxy acid 9 followed by fractional crystallization to obtain enantiomeric pure L-dioxolane. However, this strategy unnecessarily adds two extra steps of esterification and hydrolysis, which is not efficient for the large-scale synthesis of L-dioxolane. To reduce these extra steps, it is considered possible to resolve racemic 9 by forming diastereomeric salts with chiral amines. It is worth noting that compound 9 is oily in nature, and other fractional crystallization techniques may not be suitable for the resolution of chiral pure L-dioxolane (11). Singh et al. reported the chiral resolution of racemic amines via chiral pure L-(+)-tartaric acid. 22 Starting with the procedure reported by Singh et al., it is believed that a reverse strategy is adopted, namely, chiral resolution of racemic acids by forming salts with chiral pure amines (9).

[0050] To achieve the formation of diastereomeric pure salts of racemic acid 9, several (R) or (S) chiral amines were used in various solvent systems (see Table 1 below). In the investigational resolution of racemic acid 9, the formation of diastereomeric salts of 9 with (S)-phenylethylamine yielded a pure chiral dioxolane salt 10 with a diastereomeric excess (de) of 99.37% (Table 1, item 4). Racemic acid 9 was dissolved in acetonitrile and treated with 0.8 equivalents of (S)-phenylethylamine to precipitate a white salt of an acidic amine. The next objective was to determine the chiral purity of the precipitated salt and the stereoconformation of the diastereomeric salt. The precipitated diastereomeric salt was treated with 1 N HCl aqueous solution to obtain free dioxolane. The chiral purity of the obtained free dioxolane was determined by chiral HPLC, indicating that the optical purity of the precipitated isomer was 85%, and the presence of another isomer was 15%. The results of obtaining diastereomer salts by resolving racemic 9 are not encouraging, because the construction of optically pure L-BHDU requires L-dioxolane with an optical purity greater than 99% (ee ≥ 99%).

[0051] Therefore, the process of diastereomeric salt formation of racemic 9 was re-examined. To enrich the diastereomeric excess (de) of the precipitated salt (via acetonitrile), the obtained salt was resuspended in EtOAc-IPA (3:1) and stirred at room temperature for 4 hours, then filtered and neutralized with 1 N aqueous HCl solution. The chiral purity of the obtained dioxolane was re-examined by chiral HPLC, which showed ee greater than 99% (ee ≥ 99.3%), with a yield of 38%. Therefore, it was concluded that treatment with a dual solvent system, first in acetonitrile and then in EtOAc:isopropanol (3:1), unexpectedly improved the diastereomeric excess (de) of the precipitated salt (de ≥ 99.3%). The subsequent objective was to determine the stereoconformity of the precipitated salt (D- or L-type of dioxolane). X-ray crystals of the precipitated salt were cultured, and it was confirmed that the stereoconformity of the formed diastereomeric salt matched that of the L-dioxolane (10). X-ray structure shows that the hydrogen atoms present in carbon-2 (C-2) and C-3 are trans-formed to each other (see [link]). Figure 5 (b) This confirms the precipitation of L-dioxolane salt.

[0052] However, attempts were made to use the single solvent salt formation method with the various chiral amines mentioned in Table 1 below, but the results were unsatisfactory in each case. In order to improve the yield of intermediate 11, attempts were made to change the ratio of EtOAc and IPA, but in all efforts, the yield of intermediate 11 was low or the chiral purity was low.

[0053] Table 1: Formation results of racemic compound 10 with diastereomer salts of various chiral amines

[0054]

[0055] L-dioxolane compound 11 is a key intermediate in the synthesis of L-BHDU. In the presence of pyridine in acetonitrile, 11 is treated with Mn(II)OAc, acetic acid, and diacetoxyiodobenzene in 2-methylTHF, or alternatively with lead(IV)Pb(OAc)4, to convert the 2-carboxyl group of 11 to 2-acetoxy intermediate 12 at an α / β ratio of 2:1 (racemic), with a yield of 74%. Furthermore, glycosylation coupling of 12 with bromovinyluracil is carried out under Vorbrüggen coupling conditions. 23Treatment of the bromouracil base with trimethylsilyl trifluoromethanesulfonate (TMSOTf), followed by treatment with (trimethyliodosilane)TMSI, yielded in situ silylated bromovinyluracil, which condensed with acetate intermediate 12 (α / β ratio 2:1) to give coupled β and α isomers 13 (55% yield) and 14 (18% yield) in a 3:1 ratio. The isomers were separated by column chromatography to yield the desired β-isomer in 55% yield and the α-isomer in 18% yield. Finally, deprotection of the 5'-benzyl group of coupling product 13 was performed with 1 M boron trichloride (BCl3) in DCM to give the target compound L-BHDU in 60% yield. This series of reactions is described in the accompanying... Figure 4 As shown in Scheme 2.

[0056] It was determined that the exothermic final deprotection of the benzyl group in compound 13 using BCl3 was unsuitable for large-scale synthesis. To avoid using BCl3, a protecting group substitution strategy was adopted, and the 5-O-benzyl group of intermediate 11 was replaced with isobutyrate as the hydroxyl protecting group. Debenzylation of 11 under hydrogenation conditions with 5% Pd / C yielded intermediate 16 in 91% yield. Treatment of intermediate 16 with isobutyric anhydride in the presence of pyridine yielded compound 17 in 88% yield. Acylation of compound 17 followed by coupling with bromovinyluracil yielded the desired (β)nucleoside 20 (54% yield) and the undesirable (α)nucleoside 19 (22% yield) in approximately a 2:1 ratio (see [link to relevant documentation]). Figure 6 Option 3).

[0057] Deprotection of the 20 isobutyl ester group was carried out in a base (MeOH solution of 7 N NH3) to give L-BHDU in 92% yield. The optical rotation and other analytical data were consistent with those of the previously synthesized genuine L-BHDU. 24

[0058] To synthesize the POM-L-BHDU-MP prodrug, bis(POM)phosphoryl chloride (21) was first synthesized according to the scheme reported by Hawang Y. et al. 25 Next, in the presence of N-methylimidazole (NMI), L-BHDU (15) was coupled in THF with POM chloride (21) to obtain POM-L-BHDU-MP (22) in 47% yield. Figure 7 Option 4).

[0059] Conclusions

[0060] To conduct a complete biological evaluation of POM-L-BHDU-MP, an efficient and scalable synthetic method for L-BHDU was developed via commercially available (R)-2,2-dimethyl-1,3-dioxolane-4-carboxylate 7. The diastereomeric salt of racemic 9 was selectively formed via chiral (S)-phenylethylamine, followed by neutralization of 10, to yield optically pure L-dioxolane 11 (ee ≥ 99%). Compound 11 was converted to an acetate intermediate 12, which was then used for Vorbrüggen coupling with bromovinyluracil, followed by benzyl deprotection of the coupled nucleoside, yielding the target compound 15 (L-BHDU) in approximately 4.9% overall yield over seven steps. This method eliminates the costly chiral separation of racemic D and L-dioxolane and is more efficient than previously reported methods for the synthesis of L-BHDU. Further coupling of bis(POM)phosphoryl chloride 21 with L-BHDU yielded L-BHDU-monophosphate prodrug 22 (POM-L-BHDU-MP). Compared to previously reported methods, the removal of chiral separations and reduction of column chromatography in the synthetic steps, along with the use of economical reagents, make the current method suitable for large-scale preparation of POM-L-BHDU-MP and selective synthesis of chiral pure L-dioxolane (11).

[0061] During the chemical synthesis process, it was unexpectedly found that Mn(OAc)2 was a particularly effective alternative to Pb(OAc)4 for the formation of compounds 12 and 18 (converting the precursor carboxylic acid to an acetate group at the 4-position of the dioxolane moiety) and has become the preferred reagent for carrying out these steps in the scale-up reactions of the present invention. The reactivity of Mn(OAc)2 has been shown to be at least equal to, and in some cases slightly greater than, Pb(OAc)4, and it possesses other properties that make this reagent more suitable for use in the present invention than Pb(OAc)4, although Pb(OAc)4 is dominant in conventional chemistry, particularly in chemistry of this nature. Furthermore, the cost of Mn(OAc)2 is approximately 25% that of Pb(OAc)4, offering significant cost savings, especially in commercial applications. Since this reagent has much lower reagent toxicity compared to Pb(OAc)4, it is also more readily available from commercial suppliers. The reaction times for the conversion of carboxylic acid groups to acetates in compounds 12 and 18 demonstrate that Mn(OAc)2 (4 hours) is significantly faster than Pb(OAc)4 (>14 hours), which supports the accelerated synthesis of POM-L-BHDU-MP. Furthermore, in commercial applications, the handling of Mn(OAc)2 is far less challenging than that of Pb(OAc)4, as Pb(OAc)4 is highly hygroscopic (sensitive to humidity) and makes its use difficult in large quantities (>25 g), often requiring special handling, while Mn(OAc)2 is very stable (insensitive to humidity) and easy to handle.

[0062] Pb(OAc)4 is highly exothermic in reactions on a scale >50 g, and in this invention, reagents need to be added in batches to control the reaction temperature and to carry out the reaction under cooling conditions. This takes much longer than with Mn(OAc)2, because the reaction step with Mn(OAc)2 is not exothermic and does not require external cooling. In reactions using Pb(OAc)4, equimolar amounts of pyridine are required, and removal of pyridine from the reaction completion and final working product is difficult, producing a particularly pungent odor in large-scale reactions. The Mn(OAc)2 reaction does not require pyridine (or any amine), thus greatly reducing the cleanup and final treatment of the compound. Additional considerations include the fact that products obtained from the Pb(OAc)4 reaction must be purified by column chromatography to obtain sufficient purity for the next step, while Mn(OAc)2 results in a nearly clean conversion, and the crude product can be readily used in the next reaction, thus avoiding column chromatography purification. This is particularly important in the commercial application of this invention.

[0063] In this invention, under large-scale Pb(OAc)₄ reaction conditions, the formation of colloidal solutions in the reaction mixture presents challenges in handling the reaction mixture and disrupting its colloidal state during post-processing. The formation of such colloidal solutions typically impairs reaction yield. Pb(OAc)₄ reaction conditions are not eco-friendly, while those utilizing Mn(OAc)₂ are eco-friendly and substantially safe for the environment. Therefore, Mn(OAc)₂ represents a substantially better reagent for the scalable synthesis of this invention.

[0064] Example

[0065] Experimental Section

[0066] General analysis methods

[0067] Reagents and anhydrous solvents were commercially available and ready for use without further purification. Humidity-sensitive reactions were carried out in a nitrogen or argon atmosphere using oven-dried glassware. Reactions were monitored by thin-layer chromatography (TLC silica gel GF 250 μm), visualized using a Spectroline UV lamp (254 nm), and developed with a solution of 15% sulfuric acid in methanol. Column chromatography was performed on silica gel 60 Å, 40–63 µM (230 x 400 mesh, adsorbent technology). Preparative normal-phase chromatography was performed on a CombiFlash Rf 150 (Teledyne Isco) with a pre-packed RediSep Rf silica gel column or on a RediSep® gold C18 reversed-phase column. Melting points were recorded on a Mel-temp II laboratory apparatus and were uncorrected. NMR spectra were recorded at 500 MHz on a Varian Inova 500 spectrometer. 1 H NMR, recorded at 202 MHz 31 p NMR, recorded at 125 MHz 13C10 NMR, with tetramethylsilane as an internal standard. Chemical shifts (δ) are referred to as s (singlet), bs (broad singlet), d (doublet), t (triplet), q (quartet), m (multiplex), dd (double doublet), and dt (double triplet). Optical rotation was measured on a JASCO DIP-370 digital polarimeter. High-resolution mass spectrometry (HRMS) spectra were measured on a Bruker ultra-high resolution QTOF MS Impact II spectrometer. Samples were infused at 3 μL / min, and spectra were obtained in either positive or negative ionization mode, typically at a resolution of 20,000 or higher. The purity of all tested compounds was ≥95%, as determined by elemental analysis or HPLC / UV. Elemental analysis was performed by Atlantic Microlab Inc., Norcross, Georgia. HPLC / UV determinations were performed using a Waters HPLC system coupled to a photodiode array. 0.5 mg / mL sample was injected in 5 μL of a 0.5 mg / mL mixture of methanol, acetonitrile, or DMSO / MeOH (0.5:10) using an XBrigde C18 column, 3.5 μm, (4.6 x 150) mm, at 25 °C and a flow rate of 0.8 mL / min, or using an UPLC BEH C18 column, 1.7 μm, (100 x 2.1) mm, at 50 °C and a flow rate of 0.55 mL / min. The mobile phase consisted of a mixture of A = 10 mM ammonium acetate aqueous solution and B = acetonitrile (ACN), and A = 0.05% formic acid (FA) aqueous solution and B = 0.05% acetonitrile (ACN). Purity is given as a percentage of absorbance at the maximum absorption wavelength. The optical purity of the chiral intermediates and the final compound was determined by chiral HPLC. Chiral HPLC / UV determination was performed using a Waters HPLC system coupled to a photodiode array. Using a CHIRALCEL OX-H 5µmm (4.6 X 250mm) column, 10 μL of a 0.5 mg / mL sample in methanol was injected at a flow rate of 3.0 mL / min at 30 °C.

[0068] (4R)-2-((benzyloxy)methyl)-1,3-dioxolane-4-carboxylate (8): To a solution of 2-(benzyloxy)acetaldehyde (100 g, 665.91 mmol) and (R)-2,2-dimethyl-1,3-dioxolane-4-carboxylate (7, 106.65 g, 665.91 mmol) in toluene (700 mL), p-toluenesulfonic acid or Dowex 50W X8 (5.06 g, 26.63 mmol) was added, and the mixture was stirred at 80 °C for 2 hours. (The reaction mixture turned dark black). The reaction mixture was cooled to room temperature, and the evaporation was evaporated. The crude mixture was purified by rapid silica gel column chromatography (12% to 18% EtOAc / hexane) as eluent to give a non-separable mixture of (4R)-2-((benzyloxy)methyl)-1,3-dioxolane-4-carboxylate 8 as a pale yellow oil. Yield (122.5 g, 72%); 1 H NMR (500 MHz, CDCl3) δ 7.37-7.32 (m,11H), 7.30-7.27 (m, 2H), 5.33 (t, J = 4.0 Hz, 1H), 5.22 (t, J = 4.5 Hz, 1H), 4.68-4.58 (m, 7H), 4.31 (dd, J = 8.2, 7.3 Hz, 1H), 4.24 (dd, J = 8.6 & 3.9Hz, 1H), 4.13-4.09 (m, 1H), 3.99 (dd, J = 8.3 & 5.4 Hz, 1H), 3.78 (s, 3H), 3.75 (s, 3H), 3.71 (d, J = 3.8 Hz, 1H), 3.67-3.61 (m, 2H), 3.59 (d, J = 4.1Hz, 1H); 13 C NMR (125 MHz, CDCl3) δ 171.35, 171.1, 128.49, 128.46, 127.91,127.83, 127.81, 127.79, 104.87, 104.33, 74.10, 73.90, 73.80, 73.74, 70.87,70.30, 68.71, 68.31, 52.49; HRMS-ESI (m / z): [M +Na] + For C 13 H 16 The calculated value of O5Na is 275.0895; the measured value is 275.0883.

[0069] (4R)-2-((benzyloxy)methyl)-1,3-dioxolane-4-carboxylic acid (9): At 0 °C, 1 M LiOH aqueous solution (198 mL) was added dropwise to a solution of methyl (4R)-2-((benzyloxy)methyl)-1,3-dioxolane-4-carboxylic acid 8 (60 g, 237.84 mmol) in THF (250 mL), and the mixture was slowly heated to room temperature and stirred for 36 hours. THF was removed under reduced pressure, and the mixture was washed with EtOAc (3 x 75 mL). The separated aqueous layer was cooled to 0 °C, acidified to approximately pH 3 with 28% HCl aqueous solution, and extracted with DCM (3 x 125 mL). The combined organic layers were washed with brine, dried over Na2SO4, filtered, and concentrated to obtain racemic acid (4R)-2-((benzyloxy)methyl)-1,3-dioxolane-4-carboxylic acid 9, which was a light brown viscous liquid. Yield (52.5 g, 92%); 1 H NMR (500 MHz, CDCl3) δ 7.40-7.32 (m, 10H), 7.31-7.27 (m, 1H), 5.34 (t, J = 3.6 Hz, 1H), 5.20 (s, 1H), 4.74 (d, J = 12.1 Hz, 1H), 4.70-4.64 (m, 3H), 4.61 (s, 2H), 4.42-4.34 (m, 2H), 4.15-4.09 (m, 2H), 4.04 (dd, J = 8.4 & 5.4 Hz, 1H), 3.80 (dd, J = 11.4 & 1.7 Hz, 1H), 3.76 (d, J= 11.4 Hz, 1H), 3.61 (dd, J = 5.9 & 3.6 Hz, 2H); 13 C NMR (125 MHz, CDCl3) δ174.76, 173.56, 137.68, 136.02, 128.77, 128.53, 128.28, 127.91, 127.85,104.44, 104.25, 74.28, 73.83, 73.65, 70.48, 70.19, 68.27, 67.50; HRMS-ESI (m / z): [M +Na] + For C 12 H 14 The calculated value of O5Na is 261.0739; the measured value is 261.0739.

[0070] (2S,4R)-2-((benzyloxy)methyl)-1,3-dioxolane-4-carboxylate-(S)-1-phenylethyl-1-amine (10): A solution of methyl (4R)-2-((benzyloxy)methyl)-1,3-dioxolane-4-carboxylate 9 (25 g, 105.0 mmol) in ACN (50 mL) was heated to 70 °C for 20 min. Then, (S)-(-)-1-phenylethylamine (10.80 g, 89.25 mmol) was added dropwise. The mixture was heated at 70 °C for 2 h at the same temperature, then slowly cooled to room temperature and stirred for 3 h to give a white solid precipitate. The precipitate was filtered. To remove the undesirable D-dioxolane salt (15%) from the precipitate, the filtered solid was resuspended in a mixture of EtOAc:isopropanol (50 mL, 3:1) and stirred at room temperature for 4 h before filtration. The diastereomeric purity of 10 was monitored by TLC and NMR, and the process was repeated three times until the undesirable isomer (D-dioxolane salt) was completely removed from the solid precipitate. Compound 10 was obtained as a white amorphous solid. Yield (11.5 g, 32%); 1 H NMR(500 MHz, CDCl3) δ 8.37 (bs, 3H), 7.35-7.25 (m, 10H), 5.03 (t, J = 3.9 Hz,1H), 4.57-4.50 (m, 2H), 4.27-4.21 (m, 2H), 4.04 (t, J = 7.7 Hz, 1H), 3.63 (t,J = 7.1 Hz, 1H), 3.46-3.43 (m, 2H), 1.49 (d, J = 6.8 Hz, 3H); 13 C NMR (125 MHz, CDCl3) δ 176.74, 139.31, 137.81, 128.91, 128.50, 128.47, 127.89, 127.86,126.63, 103.01, 75.66, 73.373, 70.84, 68.69, 50.93, 21.13.

[0071] (2S,4R)-2-((benzyloxy)methyl)-1,3-dioxolane-4-carboxylic acid (11): (2S,4R)-2-((benzyloxy)methyl)-1,3-dioxolane-4-carboxylic acid ester (S)-1-phenylethyl-1-amine 10 (11.2 g, 31.18 mmol) was dissolved in DCM (200 mL) and washed successively with cold 1 N HCl aqueous solution (20 mL), water (100 mL), and finally with brine (100 mL). The organic layer was dried over Na2SO4, filtered, and concentrated under reduced pressure to give (2S,4R)-2-((benzyloxy)methyl)-1,3-dioxolane-4-carboxylic acid 11 as a viscous, colorless liquid. Yield (7.1 g, 95%); [α] 25 D = +20.82 (c0.5, CHCl3) 1 H NMR (500 MHz, CDCl3) δ 7.61 (bs, 1H), 7.36-7.31 (m, 4H), 7.30-7.25 (m, 1H), 5.32 (t, J = 3.5 Hz, 1H), 4.69-4.66 (m, 1H), 4.60 (s, 2H), 4.34(t, J = 7.9 Hz, 1H), 4.02 (dd, J = 8.4 & 5.4 Hz, 1H), 3.60 (dd, J = 5.9 & 3.6Hz, 2H); 13 C NMR (125 MHz, CDCl3) δ 176.74, 139.31, 137.81, 128.91, 128.50,128.47, 127.89, 127.86, 126.63, 103.01, 75.66, 73.373, 70.84, 68.69, 50.93,21.13; HRMS-ESI (m / z): [M +H] + For C 12 H 14 The calculated value of O5Na is 261.0739; the measured value is 261.0729.

[0072] (2S)-2-((benzyloxy)methyl)-1,3-dioxolane-4-yl acetate (12): A stirred solution of (2S,4R)-2-((benzyloxy)methyl)-1,3-dioxolane-4-carboxylic acid (11, 0.5 g, 2.09 mmol) in 2-Me-THF (12 mL) was degassed with argon, followed by the addition of acetic acid (0.25 mL, 42.18 mmol), Mn(II)OAc (994 mg, 5.74 mmol), and diacetoxyiodobenzene (2 g, 6.27 mmol), and degassed again for 3 minutes. The reaction mixture was heated to 65 °C under argon for 4.5 hours. The reaction mixture was cooled to room temperature and filtered through a diatomaceous earth bed. The resulting filtrate was diluted with EtOAc (60 mL); washed successively with saturated Na2S2O3 (15 mL), cold 2M NaHCO3 (15 mL), water (25 mL), and finally with saturated brine (30 mL). The organic layer was dried over Na2SO4, filtered, and concentrated under reduced pressure. The crude product was purified by rapid silica gel column chromatography using 16% to 19% EtOAc / hexane as eluent to obtain a diastereomeric mixture of (2S)-2-((benzyloxy)methyl)-1,3-dioxolane-4-ylacetate as a colorless liquid (12). Yield (385 mg, 72%); 1 H NMR (500 MHz, CDCl3) δ 7.37-7.27 (m, 8H), 6.39 (dd, J = 4.4 & 2.1 Hz,1H), 6.33 (d, J = 3.7 Hz, 0.6H), 5.38-5.36 (m, 1H), 5.30-5.27 (m, 0.7H),4.64-4.59 (m, 3H), 4.23 (dd, J = 9.5 & 4.7 Hz, 1H), 4.18 (d, J = 9.6 Hz,0.6H), 3.99-3.93 (m, 2H), 3.67-3.57 (m, 4H), 2.09 (s, 3H), 2.03 (s, 2H); 13 C{ 1 H} NMR (126 MHz, CDCl3) δ 170.4, 137.8, 128.5, 127.8, 105.3, 103.8, 94.6,94.1, 73.8, 73.8, 73.7, 71.4, 71.1, 70.9, 70.2, 21.2; HRMS-ESI (m / z): [M +Na] + For [C] 13 H 16O5] + The calculated value is 275.0895; the measured value is 275.0885.

[0073] (2S)-2-((benzyloxy)methyl)-1,3-dioxolane-4-yl acetate (12) (alternative synthesis): Pb(OAc)4 (4.46 g, 1.48 mmol) was added in portions to a stirred solution of (2S)-2-((benzyloxy)methyl)-1,3-dioxolane-4-yl acetate 11 (2.0 g, 8.39 mmol) and anhydrous pyridine (0.95 mL, 12.08 mmol) in acetonitrile (15 mL), and stirring was continued at room temperature for 16 h. The reaction mixture was filtered through a diatomaceous earth bed. The resulting filtrate was diluted with water (100 mL) and extracted with EtOAc (2 x 50 mL). The combined organic layers were washed with brine (50 mL), dried over Na2SO4, filtered, and concentrated under reduced pressure. The crude product was purified by rapid silica gel column chromatography using 15% to 18% EtOAc / hexane as eluent to obtain (2S)-2-((benzyloxy)methyl)-1,3-dioxolane-4-ylacetate 12 as a colorless liquid. Yield (1.35 g, 74%). 1 H NMR (500 MHz, CDCl3) δ 7.37-7.27 (m, 8H), 6.39 (dd, J = 4.4 & 2.1 Hz, 1H), 6.33 (d, J = 3.7 Hz, 0.6H), 5.38-5.36 (m,1H), 5.30-5.27 (m, 2.09 (s,3H), 2.03 (s, 1.6H); 13 C NMR (125 MHz, CDCl3) δ 170.04, 137.75, 128.51,127.84, 105.29, 103.81, 94.58, 94.10, 73.82, 73.82, 73.71, 71.38, 71.10,70.87, 70.16; HRMS-ESI (m / z): [M +H] + For C 13 H 16 The calculated value of O5Na is 275.0895; the measured value is 275.0884.

[0074] 1-((2S,4S)-2-((benzyloxy)methyl)-1,3-dioxolane-4-yl)-5-((E)-2-bromovinyl)pyrimidine-2,4(1H,3H)-dione (13): TBDMSOTf (1.37 mL, 5.99 mmol) and 2,4,6-trimethylpyridine (0.97 mL, 5.99 mmol) were added to a suspension of (E)-5-bromovinyluracil (500 mg, 2.30 mmol) in dry DCM (15 mL) at room temperature and stirred for 30 min. A solution of 12 (580 mg, 2.30 mmol) in DCM (20 mL) was slowly added dropwise to the resulting solution, followed by the addition of TMSI (0.36 mL, 2.53 mmol). The mixture was stirred at room temperature for 3 h and quenched with a saturated aqueous solution of Na2S2O3. The organic layer was washed with brine, dried over Na2SO4, filtered, and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (1:4 EtOAc / hexane as eluent) to give the undesirable α-isomer 14 (185 mg, 18%) as a white solid and the desired β-isomer 13 (525 mg, 55%) as a white solid. 1 HNMR (500 MHz, CDCl3) δ 8.27 (brs, 1H), 7.91 (s,1H), 7.40-7.29 (m, 6H), 6.37-6.31 (m, 2H), 5.12 (s, 1H), 4.69-4.61 (m, 2H), 4.23 (d, J = 10.1 Hz, 1H), 4.15 (dd, J = 10.2 & 5.3 Hz, 1H), 3.84 (dd, J = 5.6 & 1.8 Hz, 2H); 13 C NMR(125 MHz, CDCl3) δ 160.83, 149.26, 138.0, 136.93, 128.82, 128.52, 128.13,127.94, 111.62, 110.01, 104.91, 81.44, 74.36, 71.99, 67.99; HRMS-ESI (m / z):[M +H] + For C 17 H 17 The calculated value of BrN2O5Na is 431.0219; the measured value is 431.0209.

[0075] 5-((E)-2-bromovinyl)-1-((2S,4S)-2-(hydroxymethyl)-1,3-dioxolane-4-yl)pyrimidin-2,4(1H,3H)-dione (15): A solution of 1 M BCl3 in DCM (1.34 mL, 1.34 mmol) was added dropwise to a solution of 1-((2S,4S)-2-((benzyloxy)methyl)-1,3-dioxolane-4-yl)-5-((E)-2-bromovinyl)pyrimidin-2,4(1H,3H)-dione 13 (500 mg, 1.22 mmol) in DCM (2 mL) at -78 °C, and the mixture was stirred at the same temperature for 30 min. The reaction mixture was then quenched with MeOH (1 mL), heated to room temperature, and the inorganic salts were filtered off. The organic layer was concentrated under reduced pressure, and the crude product was purified by silica gel column chromatography (DCM / MeOH, 9:1) to give 15 (235 mg, 60%) of 1-((2S,4S)-2-((benzyloxy)methyl)-1,3-dioxolane-4-yl)-5-((E)-2-bromovinyl)pyrimidine-2,4(1H,3H)-dione as a white solid. [α] 23 D = -6.2 (c 0.2.7, MeOH); 1 H NMR (500 MHz, CDCl3) δ 11.61(brs, 1H), 8.16 (s, 1H), 7.22 (d, J = 13.6 Hz, 1H), 6.82 (d, J = 13.6 Hz,1H), 6.21 (d, J = 5 Hz, 1H), 5.31 (t, J = 6.0 Hz, 1H), 4.97-4.94 (m, 1H), 4.31 (d, J = 9.9 Hz, 1H), 4.09 (dd, J = 9.9, 5.6 Hz, 1H), 3.74-3.67 (m, 2H); 13 C NMR (125 MHz, CDCl3) δ 162.25, 150.10, 140.10, 130.35, 110.18, 107.01,105.83, 81.15, 71.07, 60.36; HRMS-ESI (m / z): [M +H] + For C 10 H 11 The calculated value of BrN2O5Na is 340.9749; the measured value is 340.9738.

[0076] (2S)-2-((benzyloxy)methyl)-1,3-dioxolane-4-ylacetate (16): A suspension of (2S)-2-((benzyloxy)methyl)-1,3-dioxolane-4-ylacetate (11, 3.0 g, 12.60 mmol) and 5% Pd / C (150 mg) in MeOH (20 mL) was treated with hydrogen at 8 psi in a Parr hydrogenator at ambient temperature for 3 h. The mixture was diluted with methanol (20 mL) and passed through a diatomaceous earth bed. The filtrate was concentrated under reduced pressure to obtain (2S,4R)-2-(hydroxymethyl)-1,3-dioxolane-4-carboxylic acid 16 as a colorless viscous liquid. Yield (1.72 g, 92%); 1 H NMR (500 MHz, CDCl3) δ5.26 (dt, J = 2.9, 11.0 Hz, 1H), 4.71 (ddd, J = 5.8, 7.3 & 17.4 Hz, 1H), 4.43-4.32 (m, 1H), 4.04 (ddd, J = 5.7, 8.4 & 29.7 Hz, 1H), 3.78-3.74 (m, 2H); HRMS-ESI (m / z): [M +H] + The calculated value for C5H8O5 is 148.0372; the measured value is 148.0364.

[0077] (2S,4R)-2-((isobutyryloxy)methyl)-1,3-dioxolane-4-carboxylic acid (17): Isobutyric anhydride (3.2 mL, 20.26 mmol) was added to a solution of (2S,4R)-2-(hydroxymethyl)-1,3-dioxolane-4-carboxylic acid 16 (2.0 g, 13.50 mmol) in dry pyridine (15 mL), followed by the addition of DMAP (8 mg), and the mixture was stirred at room temperature for 16 hours. The reaction mixture was diluted with DCM (60 mL), washed with water (2 x 25 mL), and finally washed with brine (25 mL). The organic layer was dried over Na2SO4 and concentrated under reduced pressure. The crude product was purified by rapid silica gel column chromatography using 60% to 65% EtOAc / hexane as eluent to give (2S,4R)-2-[(isobutyryloxy)methyl)]-1,3-dioxolane-4-carboxylic acid 17 as a colorless liquid. Yield (2.60 g, 88%). 1H NMR (500 MHz, CDCl3) δ 5.38 (t, J = 3.7Hz, 1H), 4.67 (dd, J = 5.1, 7.1 Hz, 1H), 4.30-4.25 (m, 1H), 4.18 (t, J = 3.6Hz, 2H), 4.02 (dd, J = 5.1 & 8.4 Hz, 1H), 2.60 (p, J = 7.0 Hz, 1H), 1.18 (d,J = 7.0 Hz, 6H); 13 C NMR (125 MHz, CDCl3) δ 173.04, 135.94, 128.88, 128.61,128.30, 104.21, 74.34, 70.60, 67.30; HRMS-ESI (m / z): [M +H] + For C9H 14 The calculated value of O6Na is 241.0688; the measured value is 241.0673.

[0078] (2S)-2-((benzyloxy)methyl)-1,3-dioxolane-4-yl acetate (18): A stirred solution of (2S,4R)-2-((isobutyryloxy)methyl)-1,3-dioxolane-4-carboxylic acid (5.0 g, 2.09 mmol) in 2-Me-THF (150 mL) was degassed with argon, followed by the addition of acetic acid (2.7 mL, 4.58 mmol), Mn(II)OAc (10.7 g, 6.19 mmol), and diacetoxyiodobenzene (22.15 g, 6.88 mmol), and degassed again for 3 minutes. The reaction mixture was heated to 65 °C under argon for 4.5 hours. The reaction mixture was cooled to room temperature and filtered through a diatomaceous earth bed. The resulting filtrate was diluted with EtOAc (160 mL); washed successively with saturated Na2S2O3 (150 mL), cold 2M NaHCO3 (150 mL), water (200 mL), and finally with saturated brine (150 mL). The organic layer was dried over Na2SO4, filtered, and concentrated under reduced pressure. The crude product was purified by rapid silica gel column chromatography using 16% to 19% EtOAc / hexane as eluent to obtain a diastereomeric mixture of (2S)-4-acetoxy-1,3-dioxolane-2-yl)methyl isobutyrate (18). Yield (4.5 mg, 84%); 1¹H NMR (500 MHz, CDCl₃) (a mixture of diastereomers) δ 6.34–6.28 (m, 1H), 5.35, 5.25 (t, J = 4.0 Hz, 1H), 4.33–3.90 (m, 4H), 2.58–2.51 (m, 1H), 2.04–2.02 (m, 3H), 1.13–1.11 (m, 6H); 13 C NMR (125 MHz, CDCl3) δ 176.5, 176.5, 170.2, 170.1, 103.6, 102.6, 102.3, 94.5, 94.0, 71.3, 70.8, 64.1, 63.5, 63.4, 63.2, 33.8, 21.1, 21.0, 18.9, 18.8; HRMS (ESI-TOF) m / z: [M + Na]+ for C 10 H 16 The calculated value of O6Na is 255.0839; the measured value is 255.0834.

[0079] (2S)-2-((benzyloxy)methyl)-1,3-dioxolane-4-yl acetate (18) (alternative synthesis): Pb(OAc)4 (3.80 g, 8.58 mmol) was added fractionally to a solution of (2S)-2-((benzyloxy)methyl)-1,3-dioxolane-4-yl acetate 17 (1.5 g, 6.87 mmol) and dried pyridine (0.78 mL, 9.90 mmol) in acetonitrile, and the mixture was stirred at room temperature for 16 hours. The reaction mixture was then passed through a diatomaceous earth bed. The filtrate was diluted with EtOAc (100 mL), washed with water (50 mL), and finally washed with brine (50 mL). The organic layer was dried over Na2SO4, filtered, and concentrated under reduced pressure. The crude product was purified by rapid silica gel column chromatography (12% to 16% EtOAc / hexane) to obtain methyl (2S)-4-acetoxy-1,3-dioxolane-2-yl)isobutyrate 18 as a colorless liquid. Yield (1.23 g, 78%). 1 ¹H NMR (500MHz, CDCl₃) (a mixture of diastereomers) δ 6.34–6.28 (m, 1H), 5.35, 5.25 (t, J = 4.0 Hz, 1H), 4.33–3.90 (m, 4H), 2.58–2.51 (m, 1H), 2.04–2.02 (m, 3H), 1.13–1.11 (m, 6H); 13C NMR (125 MHz, CDCl3) δ 176.5, 176.5, 170.2, 170.1, 103.6, 102.6, 102.3, 94.5, 94.0, 71.3, 70.8, 64.1, 63.5, 63.4, 63.2, 33.8, 21.1, 21.0, 18.9, 18.8; HRMS (ESI-TOF) m / z: [M + Na]+ for C 10 H 16 The calculated value of O6Na is 255.0839; the measured value is 255.0834.

[0080] 1-((2S,4S)-2-((benzyloxy)methyl)-1,3-dioxolane-4-yl)-5-((E)-2-bromovinyl)pyrimidine-2,4(1H,3H)-dione (20): TBDMSOTf (0.96 mL, 4.21 mmol) and 2,4,6-trimethylpyridine (0.55 mL, 4.21 mmol) were added dropwise to a suspension of (E)-5-bromovinyluracil (350 mg, 1.62 mmol) in dry DCM (12 mL) at room temperature. The reaction mixture was stirred for 30 min. Then, a solution of 18 (375 mg, 1.78 mmol) in DCM (10 mL) was added dropwise to the resulting solution, followed by the addition of TMSI (0.25 mL, 1.78 mmol). The mixture was stirred at room temperature for 3 h and quenched with a saturated aqueous solution of Na2S2O3. The organic layer was washed with brine, dried over Na2SO4, filtered, and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography (15% to 18% EtOAc / hexane) to give the undesirable α-isomer 19 (140 mg, 22%) as a white solid and the desired β-isomer 20 (340 mg, 54%) as a white solid. 1 H NMR (500 MHz, CDCl3) δ 8.27 (brs, 1H), 7.91 (s,1H), 7.40-7.29 (m, 6H), 6.37-6.31 (m, 2H), 5.12 (s, 1H), 4.69-4.61 (m, 2H), 4.23 (d, J = 10.1 Hz,1H), 4.15 (dd, J = 10.2 & 5.3 Hz, 1H), 3.84 (dd, J = 5.6 & 1.8 Hz, 2H); 13CNMR (125 MHz, CDCl3) δ 160.83, 149.26, 138.0, 136.93, 128.82, 128.52, 128.13,127.94, 111.62, 110.01, 104.91, 81.44, 74.36, 71.99, 67.99; HRMS-ESI (m / z):[M +H] + For C 17 H 17 The calculated value of BrN2O5Na is 431.0219; the measured value is 431.0210.

[0081] 5-((E)-2-bromovinyl)-1-((2S,4S)-2-(hydroxymethyl)-1,3-dioxolane-4-yl)pyrimidine-2,4(1H,3H)-dione (15): A solution of 7 N NH3 was added to a stirred solution of 1-((2S,4S)-2-((benzyloxy)methyl)-1,3-dioxolane-4-yl)-5-((E)-2-bromovinyl)pyrimidine-2,4(1H,3H)-dione (250 mg, 0.64 mmol) in MeOH (5 mL) in a sealed tube at 0 °C, and the mixture was stirred at room temperature for 16 hours. The volatiles were removed under reduced pressure, and the resulting residue was ground with diethyl ether (2 x 5 mL) to give a grayish-white solid of 1-((2S,4S)-2-((benzyloxy)methyl)-1,3-dioxolane-4-yl)-5-((E)-2-bromovinyl)pyrimidine-2,4(1H,3H)-dione (L-BHDU,15) (180 mg, 88%). [α] 23 D = -6.1 (c 0.2.7, MeOH); 1 H NMR (500 MHz, CDCl3) δ 11.61(brs, 1H), 8.16 (s, 1H), 7.22 (d, J = 13.6 Hz, 1H), 6.82 (d, J = 13.6 Hz,1H), 6.21 (d, J = 5 Hz, 1H), 5.31 (t, J = 6.0 Hz, 1H), 4.97-4.94 (m, 1H), 4.31 (d, J = 9.9 Hz, 1H), 4.09 (dd, J = 9.9, 5.6 Hz, 1H), 3.74-3.67 (m, 2H); 13C NMR (125 MHz, CDCl3) δ 162.25, 150.10, 140.10, 130.35, 110.18, 107.01,105.83, 81.15, 71.07, 60.36; HRMS-ESI (m / z): [M +H] + For C 10 H 11 The calculated value of BrN2O5Na is 340.9749; the measured value is 340.9741.

[0082] Bis(POM) prodrug of L-BHDU-MP (POM-L-BHDU-MP, 22): Bis(POM) phosphoryl chloride was added to a stirred solution of L-BHDU (15, 80 mg, 0.25 mmol) and N-methylimidazole (0.16 mL, 2.0 mmol) in dry THF (3 mL) at 0 °C. 25 21 (500 mg, 1.23 mmol) was added and stirred for 15 minutes. The reaction was then warmed to room temperature and stirred for 3 hours. The mixture was quenched with methanol and the solvent was removed under reduced pressure. The crude product was purified by silica gel column chromatography (0.5% MeOH / DCM) to give 22 as a colorless, viscous oil, which was then crystallized in DCM-pentane to give a grayish-white solid. Yield: (75 mg, 47%). Melting point: 80°C to 85°C; 1 H NMR (500 MHz, CDCl3) δ8.97 (bs, 1H), 7.71 (s, 1H), 7.45 (d, J = 13.6 Hz, 1H), 6.79 (d, J = 13.6 Hz, 1H), 6.35 (d, J = 4.5 Hz, 1H), 5.72-5.65 (m, 4H), 5.15 (s, 1H), 4.43-4.39 (m,1H), 4.35-4.31 (m, 1H), 4.26-4.21 (m, 1H), 4.20-4.17 (m, 1H), 1.23 (s, 18H); 31 P NMR (202 MHz, CDCl3) δ -3.02; 13 C NMR (125 MHz, CDCl3) δ 176.9, 161.1,149.5, 137.3, 128.4, 112.2, 110.6, 102.9, 83.2, 81.4, 71.6, 65.1, 38.9, 26.9; Anal.C 22 H32 BrN2O 12 Calculated values ​​for P: C, 42.12; H, 5.14; N, 4.47. Measured values: C, 42.34; H, 5.23; N, 4.26; HRMS (EI) for (C 22 H 32 BrN2O 12 P+H) + The calculated value is 627.0954, and the measured value m / z is 627.0953.

[0083] Auxiliary information

[0084] Additional information is available free of charge at pubs.acs.org.

[0085] Including X-ray crystallographic data for all intermediates and final compounds 3 to 28, and 1 H, 13 C and 19 A copy of the F NMR spectrum (PDF).

[0086] Access code

[0087] The CCDC contains supplemental crystallographic data for this article. This data is freely available through the website ccdc.cam.ac.uk / data_request / cif, by email at data_request@ccdc.cam.ac.uk, or by contacting the Cambridge Crystallographic Data Centre, 12 Union Road, CB2 1EZ, Cambridge, UK; Fax: +44 1223336033.

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Claims

1. A mixture of compound 9 (α and β isomers) Synthesize compounds based on chemical structure 11 The method It includes complexing compound 9 with (S)-phenylethylamine in acetonitrile as a solvent to form a phenylethylamine salt, and precipitating and / or crystallizing the phenylethylamine salt (acidic amine salt) into a mixture 10M of D and L isomers. ,as well as The salt mixture 10M of the D and L isomers was dissolved in ethyl acetate:isopropanol in a 3:1 ratio and precipitated at least twice to obtain compound 10 with a diastereomeric excess of at least 95%. The compound 10 was then washed with an aqueous acid to obtain compound 11 with a diastereomeric excess of at least 95%.

2. The method according to claim 1, wherein the mixture 10M of the D and L isomers of the acidic amine salt is dissolved in 3:1 ethyl acetate:isopropanol and precipitated at least three times, and the resulting compound 10 has at least 95% diastereomeric excess.

3. The method according to claim 2, wherein the resulting compound 10 has at least 99% diastereomeric excess.

4. The method according to claim 1, wherein the aqueous acid is 1.0 N HCl.

5. The method according to any one of claims 1 to 4, wherein said compound 11 reacts with Mn(OAc)2, diacetoxyiodobenzene and a weak acid in a solvent to form compound 12. 。 6. The method according to any one of claims 1 to 4, wherein said compound 11 reacts with lead tetraacetate (Pb(OAc)4) and a weak base to form compound 12. 。 7. The method according to claim 5 or 6, wherein tert-butyldimethylsilyl trifluoromethanesulfonate (TBDMSOTf) is used, and then compound 12 is coupled to bromovinyluracil using trimethyliodosilane (TMSI) to obtain a mixture of compounds 13 and 14. 。 8. The method according to claim 7, wherein the mixture of compounds 13 and 14 is separated by column chromatography to obtain compound 13.

9. The method according to claim 8, wherein the compound 13 is exposed to boron trichloride (BCl3) in a solvent at low temperature, followed by chromatographic separation to obtain compound LBHDU (15).

10. The method according to claim 9, wherein the LBHDU (15) is reacted with bis(POM) phosphoryl chloride in a weak base in a solvent to obtain POM-L-BHDU-MP (22).

11. A compound 16 Synthesize compounds according to chemical formula 20 The method It involves protecting the free hydroxyl group in compound 16 with an isobutyrate group to obtain compound 17. ； Compound 17 is reacted with Mn(OAc)2 and diacetoxyiodobenzene in a weak acid in a solvent to give compound 18, or compound 17 is reacted with lead tetraacetate (Pb(OAc)4) and a weak base to give compound 18. ； Compound 18 was coupled to bromovinyluracil using tert-butyldimethylsilyl trifluoromethanesulfonate (TBDMSOTf) followed by trimethyliodosilane (TMSI) to give a mixture of compounds 19 and 20. ； The mixture of compounds 19 and 20 was separated by chromatography to obtain compound 20.

12. The method according to claim 11, wherein compound 17 is reacted with Mn(OAc)2 and diacetoxyiodobenzene in a weak acid in a solvent to give compound 18.

13. The method of claim 11, wherein compounds 19 and 20 are separated using silica gel column chromatography.

14. The method of claim 11, wherein compound 20 is deprotected to remove the isobutyrate protecting group to obtain L-BHDU (15).

15. The method of claim 14, wherein the isobutyrate group is removed in ammonia / methanol.

16. The method of claim 11, wherein compound 16 is derived from compound 11. The compound 11 was prepared by reacting it with hydrogen in methane using Pd / C as a catalyst to remove the benzyl protecting group of the compound 11.

17. The method according to claim 14 or 15, wherein L-BHDU (15) is reacted with bis(POM) phosphoryl chloride in a solvent in the presence of a weak base to obtain POM-L-BHDU-MP.

18. The method according to claim 17, wherein the weak base is N-methylimidazolium (NMI) and the solvent is tetrahydrofuran (THF).

19. A compound 7 Preparation of compound 9 The method It includes reacting compound 7 with 2-(benzyloxy)acetaldehyde in a solvent. The reaction occurs in the presence of acid to form compound 8. ; and hydrolyzing the methyl ester group in compound 8 to obtain compound 9, which is a racemic mixture.

20. The method of claim 19, wherein compound 8 is purified using chromatography.

21. The method according to any one of claims 1 to 20, wherein the reaction step is performed alone or in a single pot.

22. A compound selected from the group consisting of compound 8, compound 9, compound 10M, compound 10, compound 11, compound 12, compound 13, or mixtures thereof.

23. A compound selected from the group consisting of compound 16, compound 17, compound 18, compound 20, or mixtures thereof.

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