Anodic Oxidation of 5-Aminouracil

Abstract

A method for preparing pyrimido[4,5-g]pteridine-2,4,7,9-tetrol or a salt thereof is provided. A method for preparing 3,6-diaminopyrazine-2,5-dicarboxylic acid or a salt thereof from pyrimido[4,5-g]pteridine-2,4,7,9-tetrol or a salt thereof is also provided. A method for preparing a substituted pteridine compound or a salt thereof is also provided. A method for preparing N-substituted 3,6-diaminopyrazine-2,5-dicarboxylic acid from a substituted pteridine compound or a salt thereof is also provided.

Description

[0001] Citations of Related Applications

[0002] This application claims priority to U.S. Provisional Application No. 62 / 913,196, filed on October 10, 2019, the contents of which are incorporated in their entirety. Technical Field

[0003] The field of the present disclosure relates generally to anodizing chemistry.

[0004] More specifically, the present disclosure relates to the anodic oxidation of 5-aminouracil to form potassium 4,9-dihydroxypyrimido[4,5-g]pteridine-2,7-bis(olate), which can subsequently be hydrolyzed to form 3,6-diaminopyrazine-2,5-dicarboxylic acid. 3,6-Diaminopyrazine-2,5-dicarboxylic acid is an intermediate used in the preparation of high value products such as imaging agents. Background Art

[0005] Methods for preparing potassium 4,9-dihydroxypyrimido[4,5-g]pteridine-2,7-diolate and 3,6-diaminopyrazine-2,5-dicarboxylic acid are known in the art. Problematically, prior art methods use toxic and environmentally harmful materials.

[0006] Therefore, there is a need for new processes for preparing potassium 4,9-dihydroxypyrimido[4,5-g]pteridine-2,7-diolate and 3,6-diaminopyrazine-2,5-dicarboxylic acid that reduce environmental burden and industrial hygiene issues. Summary of the invention

[0007] In some aspects of the present disclosure, a method for preparing a divalent salt of pyrimido[4,5-g]pteridine-2,4,7,9-tetraol (compound 2a) is provided. The method includes step 1a involving anodic oxidation of 5-aminopyrimidine-2,4(1H,3H)-dione (compound 1) in the presence of an aqueous base to form pyrimido[4,5-g]pteridine-2,4,7,9-tetraol (compound 2a), and step 1b involving subsequent treatment of compound 2a with a base to form compound 2, as shown below:

[0008]

[0009] Where A+ is a monovalent cation.

[0010] In some aspects of the present disclosure, a method for preparing a substituted pteridine compound or a salt thereof is provided. The method comprises step 1a involving anodic oxidation of compound 7 in the presence of a base and a solvent to form compound 8, as shown below:

[0011]

[0012] R i and R ii independently selected from: optionally substituted alkyl; optionally substituted cycloalkyl; optionally substituted aryl; optionally substituted alkoxy; optionally substituted -C(O)-alkyl; optionally substituted amino; optionally substituted polyol ethers and optionally substituted polyethers; polypeptide chain (AA); and polysaccharide chain (PS). BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Depicted are methods for preparing 3,6-diaminopyrazine-2,5-dicarboxylic acid according to the present disclosure. Figure 1 Also depicted are processes of the present disclosure for preparing (2R,2'R)-2,2'-((3,6-diaminopyrazine-2,5-dicarbonyl)bis(azanediyl))bis(3-hydroxypropionic acid) from 3,6-diaminopyrazine-2,5-dicarboxylic acid.

[0014] Figure 2 A first prior art process for preparing 3,6-diaminopyrazine-2,5-dicarboxylic acid is depicted. Figure 2 Also depicted is a prior art process for preparing (2R,2'R)-2,2'-((3,6-diaminopyrazine-2,5-dicarbonyl)bis(azanediyl))bis(3-hydroxypropionic acid) from 3,6-diaminopyrazine-2,5-dicarboxylic acid.

[0015] Figure 3 A second prior art process for preparing 3,6-diaminopyrazine-2,5-dicarboxylic acid is depicted.

[0016] Figure 4 A proposed method for preparing substituted pyrazine-2,5-dicarboxylic acids is depicted.

[0017] Figure 5 Depicted is a proposed method for preparing substituted pyrazine-2,5-dicarboxylic acids.

[0018] Figure 6 Depicted is a proposed method for preparing substituted pyrazine-2,5-dicarboxylic acids. DETAILED DESCRIPTION

[0019] The present disclosure generally relates to improved methods for preparing salts of pyrimido[4,5-g]pteridine-2,4,7,9-tetrol (Compound 2) by anodic oxidation of 5-aminouracil (5-aminopyrimidine-2,4(1H,3H)-dione) (Compound 1). In some aspects, Compound 2 can be converted by alkaline hydrolysis to form 3,6-diaminopyrazine-2,5-dicarboxylic acid (Compound 3), which is useful as an intermediate in the preparation of high-value products. In some such aspects, Compound 3 is used as an intermediate in the preparation of medical imaging agents. One such imaging agent is 3,6-diaminopyrazine-2,5-dicarboxylic acid useful as a fluorescent dye (for example and without limitation, a fluorescent dye for evaluating renal function and for imaging vasculature, such as ocular vasculature). In Figure 1 , as depicted in steps 1 and 2, the method of the present disclosure for preparing compound 3. Figure 1 , as depicted in steps 3 and 4, a specific aspect of the present disclosure relates to a method for preparing (2R,2'R)-2,2'-((3,6-diaminopyrazine-2,5-dicarbonyl)bis(azanediyl))bis(3-hydroxypropionic acid) (Compound 6) from Compound 3.

[0020] exist Figure 2 , a prior art process for preparing 3,6-diaminopyrazine-2,5-dicarboxylic acid is depicted in steps 1 and 2. In step 1, 3,6-diamino-2,5-pyrazinedicarbonitrile (compound 7) is contacted with sulfuric acid to form 3,6-diaminopyrazine-2,5-dicarboxamide (compound 8). Problematically, this prior art process starts with compound 7, which is typically prepared by complex and environmentally hazardous methods, such as taught in U.S. Pat. No. 5,294,711. US'711 teaches reacting diphenyl disulfide with hydrogen cyanide in an organic solvent (e.g., dimethoxyethane, acetonitrile, xylene, chloroform, methanol, or benzene) to form 2,3-diamino-3-(phenylthio)acrylonitrile ("DAAN"), wherein the DAAN is subsequently converted to compound 7 by contact with citric acid. In Figure 2 In step 2, compound 8 is contacted with KOH to form 3,6-diaminopyrazine-2,5-dicarboxylic acid (compound 3). Figure 2 Also depicted is a prior art method for preparing dibenzyl 2,2'-((3,6-diaminopyrazine-2,5-dicarbonyl)bis(azanediyl))(2R,2'R)-bis(3-hydroxypropionate) (Compound 5) by contacting Compound 3 with D-serine benzyl ester hydrochloride (Compound 4) in a dimethylformamide ("DMF") solvent in the presence of hydroxybenzotriazole ("HOBt", a racemization inhibitor), 1-ethyl-3-(3-methylaminopropyl)carbodiimide ("EDC", a carboxyl activator), and N,N-diisopropylethylamine ("i-PrNEt", a base). Figure 2 Also depicted is a prior art method for preparing compound 6 by contacting compound 5 with a palladium catalyst in an ethanol / water solvent.

[0021] exist Figure 3 , another prior art process for preparing 3,6-diaminopyrazine-2,5-dicarboxylic acid is depicted in steps 1 and 2. In step 1, compound 1 is contacted with potassium ferrocyanide (K3Fe(CN)6) in aqueous KOH to form potassium 4,9-dihydroxypyrimido[4,5-g]pteridine-2,7-diolate (compound 9). In step 2, compound 9 is converted to compound 3 by alkaline hydrolysis. Problematically, potassium ferrocyanide is an irritant to humans, can release toxic hydrogen cyanide upon contact with acid, and is classified as an environmental hazard due to its harmful effects on aquatic life. For example, Oskar Baudisch et al., The Oxidation of 5-Aminouracil, J. Biol. Chem., 71: 497-499 (1927), by E.C. Taylor et al., Pyrimidopteridines by Oxidative Self-condensation of Aminopyrindines, J. Am. Chem. Soc., 77, (8), 2243-2247 (1955) and by D. Kaminsky et al., Some Congeners and Analogs of Dipyridamole, J. Med. Chem., 9, 610 (1966) teach. Figure 3 of prior art methods.

[0022] The applicants have discovered an anodic oxidation process for preparing pyrimido[4,5-g]pteridine-2,4,7,9-tetrol (compound 2a) and its salts that is environmentally friendly and avoids the use of toxic and hazardous reactants. Figure 1 The reaction is depicted in steps 1a and 1b of , and generally involves anodic oxidation of compound 1 in the presence of aqueous base to form compound 2a, followed by further treatment with base to form compound 2, as shown below:

[0023]

[0024] Among them A + Yes H + The yield of compound 2 based on compound 1 is at least 20%, at least 30% or at least 40%, such as, for example, 20%, 25%, 30%, 35% or 40%.

[0025] Under one theory and without being bound by any particular theory, it is believed that the reaction mechanism for Step 1 is as follows, with the base KOH shown:

[0026]

[0027] A + Cations (e.g., K + ) relates to the stoichiometry of base to free acid. The salt form may be mono-, di-, tri- or tetra-salt.

[0028] Bases within the scope of the present disclosure include cations and anions and include inorganic bases and organic bases. Inorganic bases include sodium, potassium, ammonium, calcium, magnesium, iron, zinc, copper, manganese and aluminum salts. Non-limiting examples include: phosphates, such as dipotassium hydrogen phosphate, potassium dihydrogen phosphate, tripotassium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, trisodium phosphate, diammonium hydrogen phosphate, diammonium phosphate and triammonium phosphate; acetates, such as potassium acetate, sodium acetate and ammonium acetate; formates, such as potassium formate and sodium formate; carbonates, such as potassium carbonate, sodium carbonate, potassium bicarbonate and sodium bicarbonate; and alkali metal hydroxides, such as lithium hydroxide, sodium hydroxide, potassium hydroxide, rubidium hydroxide, cesium hydroxide, magnesium hydroxide, calcium hydroxide, manganese hydroxide (II), iron hydroxide, cobalt hydroxide, nickel hydroxide (II), copper hydroxide (II), zinc hydroxide and cadmium hydroxide. Organic bases have the general formula R-amine (e.g., R4N+OH - ) and OR - , wherein R is an organic moiety, such as an alkyl, aryl, etc. Examples of organic bases include primary, secondary, and tertiary amines; substituted amines, including naturally occurring substituted amines; and cyclic amines, such as pyridine, isopropylamine, trimethylamine, diethylamine, triethylamine, triethanolamine, diisopropylamine, ethanolamine, 2-diethylaminoethanol, trimethylamine, dicyclohexylamine, ethylenediamine, purine, piperazine, piperidine, N-ethylpiperidine, and alkali metal alcoholates (e.g., sodium methoxide). In some aspects, the base is a strong base, such as an alkali metal hydroxide base. Non-limiting examples of suitable bases include sodium hydroxide and potassium hydroxide.

[0029] In some aspects, the solvent is a polar solvent. In some aspects, the solvent is a polar protic solvent. Non-limiting examples of suitable polar protic solvents include water, methanol, ethanol, n-propanol, isopropanol, n-butanol, acetic acid, and combinations thereof. In some aspects, the solvent is water. In some aspects, the solvent is a polar solvent. In some aspects, the solvent is a polar protic solvent. Non-limiting examples of suitable polar protic solvents include water, methanol, ethanol, n-propanol, isopropanol, n-butanol, acetic acid, and combinations thereof. In some aspects, the solvent is water. In some aspects, compound 2 is the potassium salt of compound 2a as shown below:

[0030]

[0031] Potassium 4,9-dihydroxypyrimido[4,5-g]pteridine-2,7-diolate.

[0032] Electrochemical cells known in the art are generally suitable for practicing the present disclosure and may include a diaphragm or a diaphragm-free cell (divided or undivided cell, diaphragm or diaphragm-free electrolyzer). For example and without limitation, the electrochemical cell may be a diaphragm flow cell. A diaphragm flow cell generally includes two parallel rectangular electrode plates separated by a membrane generally equidistantly placed relative to each electrode. The electrode package is generally contained in a chemically stable non-conductor (e.g., polypropylene) that is constructed to accommodate both the electrode and the diaphragm, thereby allowing a separated and generally uniform solvent flow to exist on the two electrodes. A solvent flow may be generated by a circulating pump system, wherein the anolyte and the catholyte circulate through their respective compartments. A heat exchanger may be optionally integrated to maintain the reaction temperature within a specific set boundary.

[0033] In other configurations, a diaphragmless cell may be used in which the membrane or porous separator is eliminated and the electrolytic solution is allowed to pass freely between the two electrodes.

[0034] In some aspects, an indirect electrochemical system can be used. For example and without limitation, an iron (II) complex can be anodic converted to iron (III) with high current efficiency and degree (> 90%). An anodic solution containing Fe (III) can react with compound 1 to produce compound 2 or a salt thereof.

[0035] In another aspect, an electrochemical catalytic system can be used, where, for example and without limitation, an iron (II) complex can be converted to iron (III) in the presence of compound 2 to produce compound 2 or a salt thereof, regenerating Fe (II) available for reoxidation at the anode to produce more Fe (III). Thus, the reaction will be catalytic in Fe (II).

[0036] In some aspects, compound 2 can be hydrolyzed in aqueous base to form compound 3, such as Figure 1 The reaction scheme is as follows, wherein A + Yes H + or monovalent cations:

[0037]

[0038] In some such aspects, compound 2 is potassium 4,9-dihydroxypyrimido[4,5-g]pteridine-2,7-diolate. In some aspects, the base is a strong base, such as NaOH or KOH. The hydrolysis step produces compound 3 as a salt of the base cation in aqueous solution. In some other aspects, after the hydrolysis step, an acid is added to the solution to precipitate compound 3 (diacid) from the aqueous solution and form a slurry. In some aspects, the acid is a strong acid, such as, for example and without limitation, HCl. Solid compound 3 can be separated from the slurry by methods known in the art, such as filtration or centrifugation. The isolated compound 3 can be optionally further purified by washing and optionally dried.

[0039] In some aspects, compound 3 can be reacted with an NHR acid salt (compound 4) in a solvent to form the corresponding amide compound 5, such as Figure 1 As shown in step 3 in. The reaction process is as follows:

[0040]

[0041] The general method of forming an amide by coupling a compound having an amine substituent (e.g., compound 4) and a compound having a carboxyl substituent (e.g., compound 3) is known to those skilled in the art. Specifically, US 2018 / 0010881 (incorporated herein by reference in its entirety) discloses the formation of a compound, compound 3,6-diamino-N 2 ,N 5 -bis(D-serine)-pyrazine-2,5-dicarboxamide. In step 1, 3,6-diamino-N 2 ,N 5 -bis(O-benzyl-(D)-serine methyl ester)-pyrazine-2,5-dicarboxamide. A mixture of sodium 3,6-diaminopyrazine-2,5-dicarboxylate (300 mg, 1.24 mmol), (D)-Ser(OBn)-OMe-HCl salt (647 mg, 2.64 mmol), HOBt-H2O (570 mg, 3.72 mmol) and EDC-HCl (690 mg, 3.60 mmol) in DMF (25 mL) was treated with TEA (2 mL). The resulting mixture was stirred for 16 h and concentrated. The mixture was concentrated to dryness and the residue was separated with EtOAc and water. The EtOAc solution was layered and washed with saturated NaHCO3 and brine. The solution was dried over anhydrous Na2SO4, filtered and concentrated, which provided 370 mg (51% yield) of bright yellow powdered bisamide: 1NMR (300 MHz, CDCl3) δ8.47 (d, J=8.74 Hz, 2H), 7.25-7.37 (complex m, 10H), 5.98 (bs, 4H), 4.85 (dt, J=8.7, 3.3 Hz, 2H), 4.56 (ABq, J=12.6, Hz, Av=11.9 Hz, 4H), 3.99 (half of d of ABq, J=8.7, 3.3, Av is blurred, 2H), 3.76-3.80 (half of ABq-fuzzy, 2H), 3.78 (s, 6H). 13 C NMR (75 MHz, CDCl3) δ 170.5 (s), 165.1 (s), 146.8 (s), 138.7 (s) 128.6 (d), 128.1 (d), 127.8 (d), 126.9 (s), 73.5 (t), 69.8 (t), 53.0 (q), 52.9 (q). LCMS (5-95% gradient in acetonitrile with 0.1% TFA in 10 min), on a 30 mm column, single peak retention time = 4.93 min, (M+H) + = 581. In step 2, 3,6-diamino-N 2 ,N 5 -bis(O-benzyl-(D)-serine)-pyrazine-2,5-dicarboxamide. The product from step 1 (370 mg, 0.64 mmol) in THF (10 mL) was treated with 1.0 N sodium hydroxide (2.5 mL). After stirring at room temperature for 30 min, the reaction was judged complete by TLC. The pH was adjusted to about 2 by adding 1.0 N HCl, and the resulting solution was extracted with EtOAc (3×). The layers were combined, dried over sodium sulfate, filtered and concentrated to provide 353 mg (100% yield) of the diacid as an orange foam: LCMS (5-95% gradient of acetonitrile with 0.1% TFA over 10 min), retention time on a 30 mm column = 4.41 min, (M+H) + = 553. In step 3, 3,6-diamino-N 2 ,N 5 -bis(D-serine)-pyrazine-2,5-dicarboxamide. To the product from step 2 (353 mg, 0.64 mmol) in methanol (20 mL) was added 5% Pd / C (300 mg) and ammonium formate (600 mg). The resulting reaction was heated to reflux for 2 h. The reaction was cooled to room temperature, filtered through a plug of celite and concentrated. The residue was recrystallized from methanol-ether to provide 191 mg (80% yield) of yellow foamy title compound Example 2: 1NMR (300 MHz, DMSO-d6) δ8.48 (d, J=6.9 Hz, 2H), 6.72 (bs, 4H), 3.95 (obvious quartet, J=5.1 Hz, 2H), 3.60 (obvious doublet ABq; low magnetic field group concentrated at 3.71, J=9.9, 5.1 Hz, 2H; high magnetic field group concentrated at 3.48, J=20 9.9, 6.3 Hz, 2H). 13 C NMR (75 MHz, CDCl3) δ 172.9 (s), 164.9 (s), 147.0 (s), 127.0 (s), 62.9 (d), 55.7 (t). LCMS (5-95% gradient in acetonitrile with 0.1% TFA in 10 min), single peak on 30 mm column, retention time = 1.45 min, (M+H) + =373. UV / Visible (100 μM solution in PBS) λabs=434 nm. Fluorescence λex=449 nm, λem=559 nm.

[0042] Those skilled in the art will recognize that 3,6-diaminopyrazine-2,5-dicarboxylate can react with amines other than (D)-Ser(OBn)-OMe-HCl salt to form an amide having the structure of compound 6. For example, US 2018 / 0010881 also provides examples for forming amides, wherein the (D)-Ser(OBn)-OMe-HCl salt amine is replaced by (L)-Ser(OBn)-OMe-HCl, replaced by bis-2-(methoxyethyl)amine, replaced by racemic (2,2-dimethyl-1,3-dioxolan-4-yl)methanamine, replaced by tert-butyl 2-aminoethylcarbamate, replaced by Asp(OBn)-OMe-p-TosH salt, replaced by 2 -OBn-β-serine-OMe-HCl salt, replaced by m-dPEG24-amine, replaced by benzyl 3-aminopropionate p-toluenesulfonate, replaced by ethyl 4-amino-butyrate HCl salt, replaced by 3-amino-5-oxo-furan HCl salt, replaced by 3-dimethyl-β-alanine ethyl ester HCl salt, replaced by ethyl 3-(3-pyridyl)-propionate HCl salt and replaced by methyl-2-O-benzyl-3-amino-propionate HCl salt.

[0043] In some aspects, the solvent is a polar solvent. In some aspects, the solvent is a polar aprotic solvent. Non-limiting examples of suitable solvents include tetrahydrofuran, DMF, ethyl acetate and acetonitrile and combinations thereof. In some aspects, the solvent is DMF.

[0044] The reaction mixture of step 3 may also include a racemization inhibitor, such as, without limitation, HOBt, 7-aza-1-hydroxybenzotriazole, ethyl 2-cyano-2-(oxime)acetate, N-hydroxysuccinimide or hydroxy-3,4-dihydro-4-oxo-1,2,3-benzotriazine. The reaction mixture of step 3 may also include a coupling agent (such as a carboxyl activator), such as, without limitation, EDC or N,N'-dicyclohexylcarbodiimide. The reaction mixture of step 3 may also include a base, such as, without limitation, an organic amine base, such as i-PrNEt or N-methylmorpholine.

[0045] In some aspects, the NHR acid salt is a polypeptide chain comprising one or more natural or non-natural α-amino acids linked together by peptide bonds. The polypeptide chain (AA) can be a homopolymeric polypeptide chain or a heteropolypeptide chain and can be of any suitable length. For example, in some embodiments, a polypeptide chain can include 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 7, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 or 100 α-amino acids, 1 to 90 α-amino acids, 1 to 80 α-amino acids, 1 to 70 α-amino acids, 1 to 60 α-amino acids, 1 to 50 α-amino acids, 1 to 40 α-amino acids, 1 to 30 α-amino acids, 1 to 20 α-amino acids or even 1 to 10 α-amino acids. In some embodiments, the α-amino acids of the polypeptide chain (AA) are selected from aspartic acid, asparagine, arginine, histidine, lysine, glutamic acid, glutamine, serine and homoserine. In some embodiments, the α-amino acid of the polypeptide chain (AA) is selected from aspartic acid, glutamic acid, serine and homoserine. In some embodiments, the polypeptide chain (AA) refers to a single amino acid (e.g., aspartic acid or serine). In some embodiments, the amino acid is D-serine.

[0046] In some aspects, the acid salt of NHR is NHR 1 R 2 .

[0047] In these respects, R 1Each independently is -(CH2) a (CH2CH2O) b (CH2) c NR 10 CONR 11 (CH2) d (CH2CH2O) e R 20 、-(CH2) a (CH2CH2O) b (CH2) c NR 12 CSNR 13 (CH2) d (CH2CH2O) e R 21 、-(CH2) a (CH2CH2O) b (CH2) c CONR 14 (CH2) d (CH2CH2O) e R 22 、-(CH2) a (CH2CH2O) b (CH2) c NR 15 SO2(CH2) d (CH2CH2O) e R 23 、-(CH2) a (CH2CH2O) b (CH2) c SO2NR 16 (CH2) d (CH2CH2O) e R 24 、-(CH2) a (CH2CH2O) b (CH2) c NR 17 CO(CH2) d (CH2CH2O) e R 25 、-(CH2) a (CH2CH2O) b (CH2) c NR 18 CO2(CH2) d (CH2CH2O) e R 26 or -(CH2) a (CH2CH2O) b(CH2) c OC(O)NR 19 CO2(CH2) d (CH2CH2O) e R 27 ,-(CH2) c OR 68 、-CH2(CHOH) c R 69 、-CH2(CHOH) c CO2H,-(CHCO2H) c CO2H,-(CH2) c NR 70 R 71 、-CH[(CH2) f NH2] c CO2H、-CH[(CH2) f NH2] c CH2OH、-CH2(CHNH2) c CH2NR 72 R 73 、-(CH2CH2O) e R 74 ,-(CH2) t CO(CH2CH2O) e R 75 ,-(CH2) u (CH2CH2O) j (CH2) k NR 58 C(O)NR 59 (CH2) l (CH2CH2O) o R 76 ,-(CH2) u (CH2CH2O) j (CH2) k NR 60 C(S)NR 61 (CH2) l (CH2CH2O) o R 77 ,-(CH2) u (CH2CH2O) j (CH2) k C(O)NR 62 (CH2) l (CH2CH2O) o R 78 ,-(CH2) u (CH2CH2O) j (CH2) kS(O)2NR 63 (CH2) l (CH2CH2O) o R 79 、-(CH2) u (CH2CH2O) j (CH2) k NR 64 S(O)2(CH2) l (CH2CH2O) o R 80 、-(CH2) u (CH2CH2O) j (CH2) k NR 65 C(O)(CH2) l (CH2CH2O) o R 81 、-(CH2) u (CH2CH2O) j (CH2) k NR 66 C(O)O(CH2) l (CH2CH2O) o R 82 或-(CH2) u (CH2CH2O) j (CH2) k OC(O)NR 67 (CH2) l (CH2CH2O) o R 83 、-(CH2) a SO3H、-(CH2) a SO3 - 、-(CH2) a OSO3H、-(CH2) a OSO3 - 、-(CH2) a NHSO3H、-(CH2) a NHSO3 - 、-(CH2) a PO3H2、-(CH2) a PO3H - 、-(CH2) a PO3 ＝ 、-(CH2) a OPO3H2、-(CH2) a OPO3H - 或-(CH2) a OPO 3 。

[0048] R 2 , R 10 , R 11 , R 12 , R 13 , R 14 , R 15 , R 16 , R 17 , R 18 , R 19 , R 58 , R 59 , R 60 , R 61 , R 62 , R 63 , R 64 , R 65 , R 66 and R 67 Each of which is independently -H or -CH3.

[0049] R 20 , R 21 , R 22 , R 23 , R 24 , R 25 , R 26 and R 27 Each of them is independently -H, -CH3, -(CH2) f NR 28 C(O)NR 29 (CH2) g (CH2CH2O) h R 38 、-(CH2) f NR 30 CSNR 31 (CH2) g (CH2CH2O) h R 39 、-(CH2) f C(O)NR 32 (CH2) g (CH2CH2O) h R 40 、-(CH2) f S(O)2NR 33 (CH2) g (CH2CH2O) h R 41 、-(CH2) f NR 34 S(O)2(CH2) g (CH2CH2O) h R42 、-(CH2) f NR 35 C(O)(CH2) g (CH2CH2O) h R 43 、-(CH2) f NR 36 C(O)O(CH2) g (CH2CH2O) h R 44 、-(CH2) f OC(O)NR 37 (CH2) g (CH2CH2O) h R 45 , -CO(AA) or -CONH(PS).

[0050] R 28 , R 29 , R 30 , R 31 , R 32 , R 33 , R 34 , R 35 , R 36 , R 37 , R 38 , R 39 , R 40 , R 41 , R 42 , R 43 , R 44 , R 45 , R 46 , R 47 and R 48 Each of which is independently -H or -CH3.

[0051] R 68 , R 69 , R 70 , R 71 , R 72 , R 73 , R 74 , R 75 , R 76 , R 77 , R 78 , R 79 and R 80 Each of them is independently -H, -CH3, -(CH2) p S(O)2NR 84 (CH2) q (CH2CH2O) s R 81、-(CH2) p NR 85 S(O)2(CH2) q (CH2CH2O) s R 83 、-(CH2) p NR 86 C(O)(CH2) q (CH2CH2O) s R 85 、-(CH2) p NR 86 C(O)O(CH2) q (CH2CH2O) s R 87 or -(CH2) p OC(O)NR 88 (CH2) q (CH2CH2O) s R 89 .

[0052] R 81 , R 82 , R 83 , R 84 , R 85 , R 86 , R 87 , R 88 and R 89 Each of which is independently -H or -CH3.

[0053] AA is as defined above.

[0054] Each (PS) is independently a sulfated or non-sulfated polysaccharide chain comprising one or more monosaccharide units connected by glycosidic bonds. Polysaccharide chain (PS) can be any appropriate length. For example, in some embodiments, the polysaccharide chain can include 1 to 100 monosaccharide units, 1 to 90 monosaccharide units, 1 to 80 monosaccharide units, 1 to 70 monosaccharide units, 1 to 60 monosaccharide units, 1 to 50 monosaccharide units, 1 to 40 monosaccharide units, 1 to 30 monosaccharide units, 1 to 20 monosaccharide units or even 1 to 10 monosaccharide units. In some embodiments, the polysaccharide chain (PS) is a homopolymeric polysaccharide chain composed of pentose or hexose monosaccharide units. In other embodiments, the polysaccharide chain (PS) is a heteropolysaccharide chain composed of one or both of pentose and hexose monosaccharide units. In some embodiments, the monosaccharide units of the polysaccharide chain (PS) are selected from the group consisting of glucose, fructose, mannose, xylose and ribose. In some embodiments, a polysaccharide chain (PS) refers to a single monosaccharide unit (eg, glucose or fructose).

[0055] Each of t and u is independently 1, 2, 3, 4 or 5.

[0056] Each of a, d, g, l and q is independently 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.

[0057] Each of c, f, k and p is independently 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10.

[0058] Each of b, j, e, h, o, and s is independently 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99 or 100.

[0059] Each NHR moiety may optionally include a protecting group. In some such aspects, the NHR is a polypeptide chain comprising one or more natural or non-natural α-amino acids linked together by peptide bonds with protecting groups. In these aspects, the protecting group may suitably, but without limitation, benzyl ("Bn"), tert-butyl, methyl or p-methoxybenzyl.

[0060] In some aspects, each NHR is a protected single amino acid. In some such aspects, the amino acid is aspartic acid, asparagine, arginine, histidine, lysine, glutamic acid, glutamine, serine or homoserine. In some such aspects, the amino acid is aspartic acid or serine. In some embodiments, the amino acid is D-serine with a Bn protecting group.

[0061] In some aspects, compound 5 is dibenzyl 2,2'-((3,6-diaminopyrazine-2,5-dicarbonyl)bis(azanediyl))(2R,2'R)-bis(3-hydroxypropionate) having the structure:

[0062]

[0063] In the protecting group of aspects of the present disclosure, the protecting group can be cleaved from compound 5 to form compound 6, such as Figure 1As shown in step 4 in the following:

[0064]

[0065] In some aspects, compound 6 is compound 6a, (2R,2'R)-2,2'-((3,6-diaminopyrazine-2,5-dicarbonyl)bis(azanediyl))bis(3-hydroxypropionic acid) having the following structure:

[0066]

[0067] In some aspects, the solvent is a non-polar solvent. In some aspects, the solvent is a polar solvent. In some aspects, the solvent is a polar protic solvent. Non-limiting examples of suitable polar protic solvents include water, methanol, ethanol, n-propanol, isopropanol, n-butanol, acetic acid and combinations thereof. In some aspects, the solvent is ethanol and water.

[0068] Deprotection reagent can be a catalyst, acid, base or oxidant. The selection of suitable deprotection reagent depends on the characteristic of the protecting group and the protected compound. For example, some compounds or parts, such as amino acids, peptides and polypeptides may be unstable in strong acids and strong bases. In these respects, deprotection catalysts will be suitable for practicing the present disclosure. In these respects, suitable catalysts can include catalytically active metals, such as palladium, platinum, cobalt, rhodium, nickel, ruthenium, osmium, iridium and combinations thereof. In some respects, carbon-supported palladium (Pd-C) is a suitable deprotection catalyst. In some other respects, deprotection can be carried out on catalysts in the presence of hydrogen.

[0069] In some aspects, Compound 5 and Compound 6 may have a molecular weight of no more than 20,000. In some such aspects, the molecular weight is no more than 15,000, 14,000, 13,000, 12,000, 11,000, 10,000, 9,000, 8,000, 7,000, 6,000, 5,000, 4,500, 4,000, 3,500, 3,000, 2,500, 2,000, 1,500, 1,000, 900, 800, 700, 600, 500, 400, or 300. In other aspects, Compound 5 and Compound 6 may have a molecular weight greater than 20,000. In some aspects, the molecular weight is suitably about 300 to about 1,000, or about 300 to about 750. In some aspects, Compound 6 has a molecular weight of about 300 to about 600, or about 300 to about 500.

[0070] The present disclosure provides an anode method for preparing a substituted pteridine compound 8 or a salt thereof and a substituted pyrazine compound 9 or a salt thereof. The reaction flow of compound 8 is as follows:

[0071]

[0072] Without being bound by any particular theory, it is believed that the anodic oxidation of the substituted 5-aminouracil compound 7 to the substituted pteridine compound 8 proceeds according to the mechanism disclosed above and wherein R i and R ii The substituted pyrimidine heteroatom is not an atom in the bridge ring of the formed tricyclic pteridine. Under any theory for the formation of substituted pteridine compound 8, it is believed that the substitution of the indicated nitrogen heteroatoms is suitable for practicing the present disclosure because those nitrogen heteroatoms do not participate in the formation of the bridge ring in the anodic oxidation reaction. Compound 8 corresponds to the compound shown in the mechanism before keto-enol tautomerism, but one of the >NH moieties is replaced by R i Replacement, thereby forming>NR i , and the other >NH part is R ii Replacement, thereby forming>NR ii , and wherein “>” refers to a bond to a nitrogen atom.

[0073] The preparation of substituted 5-aminouracil compounds, such as compound 7, is known to those skilled in the art. See, for example, Baraldi, PG et al., Design, "Synthesis, and Biological Activity of Hybrid Compounds between Uramustine and DNA Minor Groove Binder Distamycin A", J. Med. Chem. 2002, 45, 3630-3638, the contents of which are incorporated herein in their entirety. For example, in a heterocyclic substitution reaction, 5-nitropyrimidine-2,4(1H,3H)-dione can be reacted with R in a solvent in the presence of a reducing agent. i - Leaving group and / or R ii -The leaving group reacts to form a nitrogen heteroatom replaced by R i and / or R ii Substituted 5-nitropyrimidine-2,4(1H,3H)-dione. In some aspects, the leaving group is a halogen anion, such as Br - The substitution reaction is shown below.

[0074]

[0075] The solvent can suitably be a polar aprotic solvent such as 2-methyltetrahydrofuran, tetrahydrofuran (THF), ethyl acetate, propyl acetate (e.g., isopropyl acetate, iPrOAc), acetone, dimethyl sulfoxide, N,N-dimethylformamide (DMF), acetonitrile (CH3CN), N,N-dimethylacetamide, N-methylpyrrolidone (NMP), hexamethylphosphoramide, and propylene carbonate. In some aspects, the solvent is DMF. Suitable reducing agents are known in the art. In some aspects, the reducing agent is NaH. Substituted 5-nitropyrimidine-2,4(1H,3H)-dione can be reduced with hydrogen in the presence of a suitable catalyst, such as a Pd catalyst to form compound 7a. Compound 7a can then be converted to a substituted pteridine, such as compound 8, as described elsewhere herein. In a specific aspect, such as Figure 4 As shown, 3,6-bis((2-(2-methoxyethoxy)ethyl)amino)pyrazine-2,5-dicarboxylic acid can be prepared from 5-nitropyrimidine-2,4(1H,3H)-dione and 1-bromo-2-(2-methoxyethoxy)ethane.

[0076] In some such aspects, compound 9 can be contacted with a base to form compound 10 or a salt thereof, as shown below:

[0077]

[0078] The conditions, base and solvent for the anodization reaction are as described elsewhere herein.

[0079] R i and R ii are independently selected from: hydrogen, wherein R i and R ii Only one of them can be hydrogen; optionally substituted alkyl; optionally substituted cycloalkyl or optionally substituted heterocycloalkyl; optionally substituted aryl; optionally substituted heteroaryl; optionally substituted alkoxy; optionally substituted -C(O)-alkyl; optionally substituted ester; optionally substituted amino; optionally substituted polyol ether and optionally substituted polyether; polypeptide chain (AA) as described elsewhere herein; and polysaccharide chain (PS) as described elsewhere herein. In some embodiments, R i is H. In some embodiments, R i is H and R ii is an optionally substituted ester, such as ethyl acetate. i is H and R ii is an optionally substituted polyether, such as 2-(2-methoxyethoxy)ethane or polyethylene glycol ("PEG"), such as 12PEG.

[0080] As used herein, "alkyl" refers to a monovalent straight or branched chain saturated hydrocarbon moiety consisting solely of carbon and hydrogen atoms, having 1 to 20, 1 to 10, 1 to 6, or 1 to 4 carbon atoms. Examples of alkyl groups include, but are not limited to, methyl, ethyl, propyl, isopropyl, isobutyl, sec-butyl, tert-butyl, pentyl, n-hexyl, octyl, dodecyl, and the like. As defined herein, alkyl groups may be optionally substituted.

[0081] As used herein, "cycloalkyl" refers to a carbocyclic moiety consisting of a monocycle or polycycle. As defined herein, cycloalkyl can be optionally substituted. Examples of cycloalkyl moieties include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, etc. Polycyclic structures include fused and bridged bicyclic, fused and bridged polycyclic and spirocyclic hydrocarbon ring systems, such as, for example, bicyclo [2.2.1] heptane, pinane, bicyclo [2.2.2] octane, adamantane and norbornene. Cycloalkyl can be saturated or partially unsaturated (e.g., cycloalkenyl).

[0082] As used herein, the term "heterocycloalkyl" refers to a saturated or partially unsaturated ring system radical having the indicated number of the indicated number of ring atoms and containing 1 to 5 heteroatoms selected from N, O and S, wherein the nitrogen and sulfur atoms are optionally oxidized, the nitrogen atom is optionally quaternized, such as the ring atoms (e.g., a 3- to 12-membered heterocycloalkyl having 3 to 12 ring atoms and containing at least one heteroatom, which may also be referred to as C 2-11 As defined herein, heterocycloalkyl may be optionally substituted. A "heterocycloalkyl" ring system may be a monocyclic or a fused, bridged or spiro polycyclic (including fused bicyclic, bridged bicyclic or spirocyclic) ring system.

[0083] As used herein, "aryl" refers to a group consisting of 6 to 20 carbon atoms (C6-C 20 ) is a monovalent aromatic hydrocarbon group. Aryl includes a bicyclic group comprising an aromatic ring fused to a saturated, partially unsaturated ring or an aromatic carbocyclic ring. Typical aryl groups include, but are not limited to, groups derived from benzene (phenyl), substituted benzene, naphthalene, anthracene, biphenyl, indenyl, indanyl, 1,2-dihydronaphthalene, 1,2,3,4-tetrahydronaphthyl, etc. Aryl is optionally independently substituted with one or more substituents described herein. In some aspects, aryl can be substituted by alkyl, cycloalkyl, halogen or haloalkyl. Alkyl can be directly substituted with nitrogen, or can be connected to nitrogen by alkyl or substituted alkyl.

[0084] As used herein, the term "heteroaryl" refers to an aryl ring containing 1 to 5 heteroatoms selected from N, O and S, wherein the nitrogen and sulfur atoms are optionally oxidized, and the nitrogen atom is optionally quaternized. The heteroaryl group can be attached to the rest of the molecule through a heteroatom. The heteroaryl group is optionally substituted independently with one or more substituents described herein.

[0085] As used herein, "alkoxy" refers to a moiety having the structure -OR, wherein R is an alkyl moiety as defined herein. Examples of alkoxy moieties include, but are not limited to, methoxy, ethoxy, isopropoxy, and the like.

[0086] As used herein, "haloalkyl" refers to an alkyl as defined herein in which one or more hydrogen atoms have been replaced by the same or different halogens. Exemplary haloalkyls include -CH2Cl, -CH2CF3, -CH2CCl3, -CF3, CHF2, etc.

[0087] As used herein, "-C(O)-alkyl" refers to an optionally substituted aldehyde moiety that forms an amide with an azo group, i.e., >NC(O)-alkyl. Non-limiting examples of substituted NC(O)-alkyls include amide-alcohols, amide-diols, amide-polyols, and derivatives thereof.

[0088] As used herein, "polyol ethers" and "polyethers" have the general structure wherein nitrogen refers to the ring atom to which the polyol ether or polyether is attached.

[0089]

[0090] Where: R a is optionally substituted C 1-4 Alkyl; R b is optionally substituted C 1-4 Alkyl; R c is optionally substituted C 1-4 alkyl; and R d is optionally substituted C 1-4 alkyl or hydrogen. x is 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90 or 100 and any ranges thereof, such as, for example, 1 to 100, 1 to 70, 1 to 50, 1 to 30, 1 to 20, 2 to 20, 2 to 10, 3 to 20, 3 to 10, 5 to 20 or 5 to 10. In some aspects, R a To R c C2 and R d Is H or C 1-2 In one example, the polyether is PEG. In some non-limiting aspects, the branched polyols and branched polyethers have the general structure shown below, wherein the nitrogen atom refers to the ring atom to which the polyol ether or polyether is attached.

[0091]

[0092] Where R dAs defined herein, and y is 1, 2, 3, 4, 5, 10, 15, 20, 25, 30, 35, 40, 45 or 50 and any ranges thereof, such as, for example, 1 to 50, 1 to 30, 1 to 20, 2 to 20, 2 to 10, 3 to 20, 3 to 10, 5 to 20 or 5 to 10. Non-limiting examples include the following structures, wherein nitrogen refers to the ring atom to which the polyol ether or polyether is attached

[0093]

[0094] As used herein, "halogen" refers to chlorine, fluorine, bromine, and iodine.

[0095] As used herein, "amino" refers to an amino group of the structure -NR x R y part, where R x and R y The term "monoalkylamino" refers to a structure in which R x and R y One is hydrogen and R x and R y The other of which is an alkyl group, and "dialkylamino" refers to structures in which R x and R y Each of is an alkyl group.

[0096] As used herein, "optionally substituted" as used herein refers to a moiety that can be unsubstituted or substituted with a specified group. Examples of substituents include, but are not limited to, hydroxy, alkyl, alkoxy, halo, haloalkyl, oxo, amino, monoalkylamino, or dialkylamino.

[0097] In some such aspects, compound 10 or a salt thereof can be reacted with an NHR acid salt (compound 4) in a solvent to form compound 11 or a salt thereof as shown below:

[0098]

[0099] In conjunction with the preparation of compound 5 by reaction of compound 3 with compound 4, R and R were previously defined. ii and said reaction.

[0100] In aspects of the present disclosure, each HNR moiety includes a protecting group PG, and the protecting group is cleaved as described below and as described elsewhere herein in conjunction with compounds 5 and 6 to form compound 13 or a salt thereof.

[0101]

[0102] Example

[0103] Example 1

[0104] Potassium 4,9-dihydroxypyrimido[4,5-g]pteridine-2,7-diolate was prepared according to the following reaction scheme:

[0105]

[0106] In the first (anode) chamber, the inner wall of a Baumer beaker (tall type, 400 mL) was mounted with a platinum-coated titanium expanded screen, and a graphite felt anode was placed uniformly thereon and lined the inner wall. A stainless steel cathode formed by a 0.25-inch tube was placed in a separate (cathode) chamber formed by a PVC tube having an outer diameter of about 3 / 4 inch (1.9 cm) and a length of about 6 inches (15.24 cm) sealed at one end with clear room temperature vulcanized ("RTV") silicone. The tube was perforated by drilling holes at uniform intervals of 1 / 4 inch (0.64 cm) to a distance of about 4 inches (10.2 cm) from the bottom of the RTV plug. A 0.15 mm (0.006 inch) thick Nafion N324 membrane, Teflon TM Fabric reinforced (Rf[OCF2CF(CF3)2] n OCF2CF2SO3H) is wrapped around a PVC support tube, with the rough side facing the cathode, and then sealed with silicone RTV, being careful not to pollute the exposed Nafion surface by RTV. The Nafion membrane is configured to surround the tube and prevent mixing between the two chambers, but allows charge transfer between the two chambers. The Nafion membrane is pretreated by immersing in a KOH solution contained in a 100mL graduated cylinder (stirring the solution vortex by hand). The membrane begins to shrink to about half of its original diameter, and then expands until it contacts the graduated cylinder wall. The membrane is soaked for more than 0.5 hours. Thereafter, it is removed and rinsed with deionized water. The membrane is kept moist by being stored in a plastic pouch. The battery is constructed so that the graphite felt anode has a space of about 0.5 inches (1.27cm) at the bottom, where a magnetic stirring bar is placed. By connecting it to a three-claw clamp, the cathode chamber tube is suspended in the middle of the beaker (anode) assembly.

[0107] The assembled 2-chamber cell was charged with aqueous KOH (4.2 g KOH in 160 mL deionized water) to approximately equal levels in both chambers. 5-aminopyrimidine-2,4(1H,3H)-dione (5-aminouracil) (2.0 g, 0.0157 moles) was added to the anolyte and allowed to dissolve. A DC power supply (Lambda, LG-532 model) was connected and 1.0 A (5.6 V) was passed through the cell with continuous stirring until a charge of two farads was passed (0.9 h). During the reaction, the anolyte turned red (from its initial yellow).

[0108] The anolyte and catholyte were analyzed for the presence of the desired product by reverse phase high performance liquid chromatography ("reHPLC"). The anolyte was confirmed to show a large amount of potassium 4,9-dihydroxypyrimido[4,5-g]pteridine-2,7-diolate. The catholyte was not found to contain a detectable amount of potassium 4,9-dihydroxypyrimido[4,5-g]pteridine-2,7-diolate.

[0109] Example 2

[0110] 3,6-Diaminopyrazine-2,5-dicarboxylic acid was prepared from potassium 4,9-dihydroxypyrimido[4,5-g]pteridine-2,7-diolate according to the following reaction scheme:

[0111]

[0112] In each of two Teflon reaction vessels was placed 0.5 g of potassium 4,9-dihydroxypyrimido[4,5-g]pteridine-2,7-diolate and a solution containing 0.3 to 0.4 g of sodium hydroxide in 10 mL of deionized water. The vessels were fixed in a microwave reactor and allowed to react at 170°C and about 100 psig pressure for 1 hour. The vessel was cooled to about 50°C and the contents were filtered to remove a small amount of solid residue. The bright yellow filtrate was transferred to a 250 mL round bottom flask equipped with a large magnetic stirring bar. The pH was adjusted to about 3 with concentrated HCl while stirring, resulting in the formation of a large red precipitate. A few drops of acid were added and the solids were collected by filtration on a sintered glass, washed with cold 1N HCl (1×10 mL), acetonitrile (2×30 mL) and diethyl ether (1×30 mL), drained and transferred to a vacuum oven. The collected solid was dried at 45-50°C overnight to obtain 0.48 g of 3,6-diaminopyrazine-2,5-dicarboxylic acid (79%). 13 NMR (D2O / NaOD, TMS external standard) δ132.35, 147.32, 171.68.

[0113] Example 3

[0114] An IKA ElectraSyn Pro-Divide two-chamber cell equipped with a 5u porous polypropylene sintered separator and a stirring bar was charged with 5-aminouracil potassium salt (0.10 g) in 13.0 mL of deionized water, so that there was 6.5 mL in each of the two cell chambers. The anode was reticulated carbon foam, and the anode chamber was equipped with a thermocouple. The cathode was stainless steel.

[0115] Oxidation was carried out under constant current conditions (13 mA) for 100 minutes, at which time 62% of 5-aminouracil had been consumed. The major product, 1,6-dihydropyrimido[4,5-g]pteridine-2,4,7,9(3H,8H)-tetraone, was quantified by HPLC and was determined to have been produced in 22% yield (7 mg) based on the consumed 5-aminouracil.

[0116] Example 4

[0117] The conditions of Example 3 were repeated except that a reticulated carbon foam anode of the same size was used in place of the anode. The reaction progress was checked at 32% conversion of 5-aminouracil and it was determined that 11.2 mg of 1,6-dihydropyrimido[4,5-g]pteridine-2,4,7,9(3H,8H)-tetraone had been produced.

[0118] Example 5

[0119] The conditions of Example 4 were repeated, but the electrode polarity was reversed every 10 seconds. The yield of 1,6-dihydropyrimido[4,5-g]pteridine-2,4,7,9(3H,8H)-tetraone was 26% based on the amount of 5-aminouracil consumed.

[0120] Example 6

[0121] The conditions of Example 3 were repeated, but 27 mg of potassium ferrocyanide was added to the anolyte. The yield of 1,6-dihydropyrimido[4,5-g]pteridine-2,4,7,9(3H,8H)-tetraone was 39.2% based on the amount of 5-aminouracil consumed.

[0122] Example 7

[0123] The conditions of Example 3 were repeated, but using controlled anode potential conditions instead of the controlled current conditions used in Example 3. The anode potential was maintained at 1.5 V relative to Ag. o / 1.2 V against AgCl reference electrode. After 140 min, the yield of 1,6-dihydropyrimido[4,5-g]pteridine-2,4,7,9(3H,8H)-tetraone was 41% by quantitative rpHPLC analysis based on the amount of 5-aminouracil consumed.

[0124] Example 8

[0125] The conditions of Example 3 were repeated except that the anode was replaced with the following materials, each in a separate experiment: glassy carbon, graphite, and platinum. Yields of 1,6-dihydropyrimido[4,5-g]pteridine-2,4,7,9(3H,8H)-tetraone similar to those of Example 3 were obtained for each of the anodes evaluated.

[0126] Example 9

[0127] The conditions of Example 3 were repeated except that the porous polypropylene sintered separator was removed, thereby providing a membrane-less cell. A 10% yield of 1,6-dihydropyrimido[4,5-g]pteridine-2,4,7,9(3H,8H)-tetraone was achieved based on the amount of 5-aminouracil consumed.

[0128] Example 10 (Prophetic): Preparation of 1,6-bis(2-(2-methoxyethoxy)ethyl)-1,6-dihydropyrimido[4,5-g]pteridine-2,4,7,9(3H,8H)-tetraone (14)

[0129] like Figure 4 As shown in step 1, 5-nitropyrimidine-2,4(1H,3H)-dione (14) can be reacted with 1-bromo-2-(2-methoxyethoxy)ethane (15) according to the procedure listed in the experimental section of the general procedure for the synthesis of compound 4-9 on page 3634 of Baraldi, PG et al., J. Med. Chem., 2002, 45, 3630-3638, thereby producing 1-(2-(2-methoxyethoxy)ethyl)-5-nitropyrimidine-2,4(1H,3H)-dione (16).

[0130] like Figure 4 As shown in Step 2, compound 16 can be reduced to 5-amino-1-(2-(2-methoxyethoxy)ethyl)pyrimidine-2,4(1H,3H)-dione (17) using 10% carbon-supported Pd and hydrogen in a suitable solvent such as 2-methoxyethanol using essentially Baraldi's conditions, the general procedure for the synthesis of compounds 10-15 in the reference cited in Step 1 on page 3635.

[0131] like Figure 4 As shown in Step 3, electrochemical anodic oxidation of 5-amino-1-(2-(2-methoxyethoxy)ethyl)pyrimidine-2,4(1H,3H)-dione (17) can be carried out using conditions essentially those of Examples 1-9, which will produce 1,6-bis(2-(2-methoxyethoxy)ethyl)-1,6-dihydropyrimido[4,5-g]pteridine-2,4,7,9(3H,8H)-tetraone (18) which can be separated by reverse phase high pressure liquid chromatography, by rpHPLC, or by precipitation techniques known in the art.

[0132] Example 11 (Prophetic): Preparation of 3,6-bis((2-(2-methoxyethoxy)ethyl)amino)pyrazine-2,5-dicarboxylic acid (20)

[0133] like Figure 4As further shown in Example 2, 1,6-bis(2-(2-methoxyethoxy)ethyl)-1,6-dihydropyrimido[4,5-g]pteridine-2,4,7,9(3H,8H)-tetraone (18) can be converted to 3,6-bis((2-(2-methoxyethoxy)ethyl)amino)pyrazine-2,5-dicarboxylic acid (20) using essentially the conditions of Example 2.

[0134] Example 12 (Prophetic): Preparation of diethyl 2,2'-(2,4,7,9-tetraoxo-2,3,4,7,8,9-hexahydropyrimido[4,5-g]pteridine-1,6-diyl) diacetate (24)

[0135] like Figure 5 , as shown in Step 1, according to the procedure of Baraldi listed in the Experimental section of the General Procedure for the Synthesis of Compounds 4-9 on page 3634, 5-nitropyrimidine-2,4(1H,3H)-dione (14) can be reacted with ethyl bromoacetate (21) to produce ethyl 2-(5-nitro-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)acetate (22).

[0136] like Figure 5 As shown in Step 2, compound 22 can be reduced to ethyl 2-(5-amino-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)acetate (23) using 10% carbon-supported Pd and hydrogen in a suitable solvent such as 2-methoxyethanol using conditions essentially following the general procedure for the synthesis of compounds 10-15 in the reference cited in Step 1 on page 3635.

[0137] like Figure 5 As shown in Step 3, electrochemical anodic oxidation of ethyl 2-(5-amino-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)acetate (23) can be carried out using conditions essentially those of Examples 1-9 to produce diethyl 2,2'-(2,4,7,9-tetraoxo-2,3,4,7,8,9-hexahydropyrimido[4,5-g]pteridine-1,6-diyl)diacetate (24) which can be separated by rpHPLC, normal phase silica gel chromatography, or by precipitation techniques known in the art.

[0138] Example 13 (Prophetic): Generation of diethyl 2,2'-((3,6-dicarbamoylpyrazine-2,5-diyl)bis(azanediyl))diacetate (26).

[0139] like Figure 5As further shown in Example 2, the conversion of diethyl 2,2'-(2,4,7,9-tetraoxo-2,3,4,7,8,9-hexahydropyrimido[4,5-g]pteridine-1,6-diyl)diacetate (24) to diethyl 2,2'-((3,6-dicarbamoylpyrazine-2,5-diyl)bis(azanediyl))diacetate (26) can be carried out using essentially the conditions of Example 2.

[0140] Example 14 (Prophetic): Preparation of 1,6-bis(2,5,8,11,14,17,20,23,26,29,32,35-dodeca-triacontane-37-yl)-1,6-dihydropyrimido[4,5-g]pteridine-2,4,7,9(3H,8H)-tetraone (32)

[0141] like Figure 6 , as shown in Step 1, according to the procedure of Baraldi listed in the Experimental section of the General Procedure for the Synthesis of Compounds 4-9 on page 3634, 5-nitropyrimidine-2,4(1H,3H)-dione (14) can be reacted with m-12PEG-bromide (27) to produce 1-(2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxatriacont-37-yl)-5-nitropyrimidine-2,4(1H,3H)-dione (28).

[0142] like Figure 6 As shown in Step 2, compound 24 can be reduced to 5-amino-1-(2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxatriacont-37-yl)pyrimidine-2,4(1H,3H)-dione (29) using 10% carbon-supported Pd and hydrogen in a suitable solvent such as 2-methoxyethanol and essentially the Baraldi conditions for the synthesis of compounds 10-15 in Step 1 on page 3635 of the cited reference.

[0143] like Figure 6 Electrochemical anodic oxidation of 5-amino-1-(2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxatriacontane-37-yl)pyrimidine-2,4(1H,3H)-dione (29) using essentially the conditions of Examples 1-9, as shown in Step 3, will produce 1,6-bis(2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxatriacontane-37-yl)-1,6-dihydropyrimido[4,5-g]pteridine-2,4,7,9(3H,8H)-tetraone (30) which can be isolated by rpHPLC, normal phase silica gel chromatography, or by precipitation techniques known in the art.

[0144] Example 15 (Prophetic): Preparation of 1,6-bis(2,5,8,11,14,17,20,23,26,29,32,35-dodeca-heptatriacontane-37-yl)-1,6-dihydropyrimido[4,5-g]pteridine-2,4,7,9(3H,8H)-tetraone (32).

[0145] like Figure 6 As further shown, the conversion of 1,6-bis(2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxatriacontane-37-yl)-1,6-dihydropyrimido[4,5-g]pteridine-2,4,7,9(3H,8H)-tetraone (30) to 1,6-bis(2,5,8,11,14,17,20,23,26,29,32,35-dodecaoxatriacontane-37-yl)-1,6-dihydropyrimido[4,5-g]pteridine-2,4,7,9(3H,8H)-tetraone (32) can be carried out using essentially the conditions of Example 2.

[0146] This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any introduced methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.

Claims

1. A method for preparing a divalent salt of compound 2: pyrimido[4,5-g]pteridine-2,4,7,9-tetraol, the method comprising step 1a, wherein step 1a involves anodic oxidation of compound 1: 5-aminopyrimidine-2,4(1H,3H)-dione in the presence of aqueous KOH to form compound 2a: pyrimido[4,5-g]pteridine-2,4,7,9-tetraol; followed by step 1b, wherein step 1b involves treating compound 2a with KOH to form compound 2, as shown below: in, A + It is a monovalent potassium ion.

2. The method according to claim 1, wherein: Step 1a and step 1b are performed in an electrochemical cell.

3. The method according to claim 2, wherein: The electrochemical cell comprises a diaphragm cell.

4. The method according to claim 2, wherein: The electrochemical cell comprises a separatorless cell.

5. The method according to claim 1 further comprises hydrolyzing compound 2 in the presence of NaOH to form compound 3: 3,6-diaminopyrazine-2,5-dicarboxylic acid as shown below:

6. The method according to claim 5, further comprising reacting 3,6-diaminopyrazine-2,5-dicarboxylic acid with an acidic salt of compound 4:NHR in a dimethylformamide solvent to form compound 5, as shown below: in, NHR is each independently D-serine, and PG is a benzyl protecting group.

7. The method according to claim 6, wherein: The protecting group is cleaved to form compound 6 as shown below: Among them, compound 6 is (2R,2'R)-2,2'-((3,6-diaminopyrazine-2,5-dicarbonyl)bis(azanediyl))bis(3-hydroxypropionic acid) having the following structure: wherein the deprotecting agent is a catalyst comprising palladium and the solvent is an ethanol / water solvent.

8. A method for preparing a substituted pteridine compound or a salt thereof, the method comprising step 1a, wherein step 1a involves anodic oxidation of compound 7 in the presence of aqueous KOH to form compound 8, as shown below: in, R i and R ii Each is hydrogen; Among them, compound 7 is 5-aminopyrimidine-2,4(1H,3H)-dione, and compound 8 is 1,6-dihydropyrimido[4,5-g]pteridine-2,4,7,9(3H,8H)-tetraone.

9. The method according to claim 8, further comprising step 1b, wherein step 1b involves contacting compound 8 with aqueous KOH to form compound 9, as shown below: 。 10. The method according to claim 9, further comprising contacting compound 9 with aqueous KOH to form compound 10, as shown below: in, Compound 10 is 3,6-diaminopyrazine-2,5-dicarboxylic acid.

11. The method according to claim 10, further comprising reacting compound 10 with NHR acid salt compound 4 in dimethylformamide solvent to form compound 11, as shown below: in, Each NHR is independently D-serine comprising a benzyl protecting group PG.

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