2-Methylpropyl ester of 3-(adenin-9-yl)-2-hydroxypropanoic acid. Mechanism of antiviral action in vaccinia virus-infected L929 cells

A novel type of acyclic nucleoside phosphonates derived from 2-(phosphonomethoxy)propanoic acid

A convenient and efficient synthesis of a novel class of acyclic nucleoside phosphonates derived from 2-(phosphonomethoxy)propanoic acid has been developed. The key step of the synthesis is the optimized oxidation of the 3-hydroxy-2-(phosphonomethoxy)propyl (HPMP) analogues to the corresponding 2'-carboxy-PME (CPME) derivatives using the TEMPO/NaClO₂/NaClO oxidizing system. Although (S)-3-(adenin-9-yl)-2-(phosphonomethoxy)propanoic acid ((S)-CPMEA) has been designed as a compound with potential anti-HIV activity, none of the newly prepared CPME analogues exhibited any antiviral activity.

Synthesis of acyclic analogs of adenosine

This unit describes preparation of two groups of chiral acyclic nucleosides that are N-alkyl derivatives of adenine with hydroxyl group(s) on the alkyl chain. As an example of the neutral group, the synthesis is presented for (S)-(2,3,dihydroxypropyl)adenine (DHPA), a compound with multiple biological effects in proliferating systems. Its synthesis consists of alkylation of adenine with a suitable chiral synthon based on 1,2-O-isopropylideneglycerol. Another group of structurally related biologically active compounds are the 9-alkyladenines bearing both hydroxyl and carboxyl functions. Large-scale cyanohydrin reaction of the adenine-containing acetaldehyde intermediate yields 3-(adenine-9-yl)-2-hydroxypropanoic acid (AHPA). Lastly, one of the alternative syntheses of its homolog, the nucleoside antibiotic eritadenine (with a D-erythro-2,3-dihydroxybutanoic acid side-chain) is described starting from d-ribose. Procedures for preparation of all intermediates as well as the purification of the resulting crude material are described in detail. All these adenine derivatives inhibit SAM-dependent methylation reactions via inhibition of SAH hydrolase.

Synthesis of base substituted 2-hydroxy-3-(purin-9-yl)-propanoic acids and 4-(purin-9-yl)-3-butenoic acids

Alkylation of 6-chloropurine and 2-amino-6-chloropurine with bromoacetaldehyde diethyl acetal afforded 6-chloro-9-(2,2-diethoxyethyl)purine (3a) and its 2-amino congener (3b). Treatment of compounds 3 with primary and secondary amines gave the N6-substituted adenines (5a-5c) and 2,6-diaminopurines (5d-5f). Hydrolysis of 3 resulted in hypoxanthine (6a) and guanine (6b) derivatives, while their reaction with thiourea led to 6-sulfanylpurine (7a) and 2-amino-6-sulfanylpurine (7b) compounds. Treatment with diluted acid followed by potassium cyanide treatment and acid hydrolysis afforded 6-substituted 3-(purin-9-yl)- and 3-(2-aminopurin-9-yl)-2-hydroxypropanoic acids (8-10). Reaction of compounds 3 with malonic acid in aqueous solution gave exclusively the product of isomerisation, 6-substituted 4-(purin-9-yl)-3-butenoic acids (15).

New 2-Alkynyl Derivatives of the Acyclic Nucleoside 9-(2,3-Dihydroxypropyl)adenine and Their 6-Guanidinopurine Counterparts as Potential Effectors of Adenosine Receptors

A series of the new 2-alkynyl derivatives of the acyclic nucleoside 9-(2,3-dihydroxypropyl)- adenine and their 6-guanidinopurine analogues were prepared by the Sonogashira coupling. The effect of the prepared compounds on A1 and A2A receptors was examined.

Synthesis of Acyclic Adenine 8,N-Anhydronucleosides

9-(4-Hydroxybutyl)adenine (10) was obtained by reaction of adenine with 4-[(2-tetrahydropyran-2-yl)oxy]butyl chloride (7) in the presence of DBU. 8-Bromo-9-(4-hydroxybutyl)adenine (13) was prepared by bromination of 10 or by alkylation of 8-bromoadenine (11) with 4-bromoethyl acetate followed by methanolysis. Tosylation of compound 13 afforded the 4-tosyloxy derivative 15 which gave on heating with methylamine or cyclopropylamine 6-methyl- (17a) or 6-cyclopropyl-7,8,9,10-tetrahydro-6H-[1,3]diazepino[1,2-e]purin-4-amine (17b), while the reaction with hydrazine afforded 7,8,9,10-tetrahydro-6H-[1,3]diazepino[1,2-e]purine-4,6-diamine (17d). Treatment of compound 13 with thionyl chloride gave 9-(4-chlorobutyl)-8-chloroadenine (18) as the main product which was transformed to 17b, 6-propyl-7,8,9,10-tetrahydro-6H-[1,3]diazepino[1,2-e]purin-4-amine (17c) or 7,8,9,10-tetrahydro-6H-[1,3]diazepino[1,2-e]purin-4-amine (17e) by reaction with cyclopropylamine, propylamine or ammonia, respectively. Compound 17e was quite stable both in acid and alkaline solutions, at room temperature or at 90 °C. Compound 13 was converted to 9-(4-hydroxybutyl)-8-methylaminoadenine (19) by reaction with methylamine. Compound 19 failed to undergo intramolecular cyclization to diazepine 17a on treatment with diphenyl carbonate, bis(4-nitrophenyl) carbonate or 1,1'-carbonyldiimidazole.

Inhibitory activity of S-adenosylhomocysteine hydrolase inhibitors against human cytomegalovirus replication

Various acyclic and carbocyclic adenosine analogues, which are apparently targeted at the S-adenosylhomocysteine (AdoHcy) hydrolase have been reported to inhibit the replication of a number of pox-, rhabdo-, paramyxo-, arena-, and reoviruses. Here we show that this activity spectrum extends to human cytomegalovirus (HCMV). Of the compounds tested, neplanocin A, 3-deazaneplanocin A, 6'-C-methylneplanocin A and 5'-noraristeromycin were found to be the most potent inhibitors of HCMV replication in vitro. Their 50% inhibitory concentration ranged from 0.05 to 1.35 micrograms/ml. In general, the anti-HCMV activity of the adenosine analogues correlated well with their affinity (Ki) for AdoHcy hydrolase, suggesting that AdoHcy hydrolase may be considered as a target enzyme for anti-HCMV agents. For four compounds (3-deazaneplanocin A, 6'-C-methylneplanocin A (isomers I and II) and 3-deazaadenosine), anti-HCMV potency was greater than could be expected solely from their interaction with AdoHcy hydrolase, suggesting that these compounds may be functioning by an additional mechanism.

Antiviral agents: characteristic activity spectrum depending on the molecular target with which they interact

The target protein (enzyme) with which antiviral agents interact determines their antiviral activity spectrum. Based on their activity spectrum, antiviral compounds could be divided into the following classes: (1) sulfated polysaccharides (i.e., dextran sulfate), which interact with the viral envelope glycoproteins and are inhibitory to a broad variety of enveloped viruses (i.e., retro-, herpes-, rhabdo-, and arenaviruses): (2) SAH hydrolase inhibitors (i.e., neplanocin A derivatives), which are particularly effective against poxvirus, (-)RNA viruses (paramyxovirus, rhabdovirus), and (+/-)RNA virus (reovirus); (3) OMP decarboxylase inhibitors (i.e., pyrazofurin) and CTP synthetase inhibitors (i.e., cyclopentenylcytosine), which are active against a broad range of DNA, (+)RNA, (-)RNA, and (+/-)RNA viruses; (4) IMP dehydrogenase inhibitors (i.e., ribavirin), which are also active against various (+)RNA and (-)RNA viruses and, in particular, ortho- and paramyxoviruses; (5) acyclic guanosine analogs (i.e., ganciclovir) and carbocyclic guanosine analogs (i.e., cyclobut-G), which are particularly active against herpesviruses (i.e., HSV-1, HSV-2, VZV, CMV); (6) thymidine analogs (i.e., BVDU, BVaraU), which are specifically active against HSV-1 and VZV because of their preferential phosphorylation by the virus-encoded thymidine kinase; (7) acyclic nucleoside phosphonates (i.e., HPMPA, HPMPC, PMEA, FPMPA), which, depending on the structure of the acyclic side chain, span an activity spectrum from DNA viruses (papova-, adeno-, herpes-, hepadna-, and poxvirus) to retroviruses (HIV); (8) dideoxynucleoside analogs (i.e., AZT, DDC), which act as chain terminators in the reverse transcriptase reaction and thus block the replication of retroviruses as well as hepadnaviruses; and (9) the TIBO, HEPT, and other TIBO-like compounds, which interact specifically with the reverse transcriptase of HIV-1 and thus block the replication of HIV-1, but not of HIV-2 or any other retrovirus.

Correlation between the antiviral activity of acyclic and carbocyclic adenosine analogues in murine L929 cells and their inhibitory effect on L929 cells S-adenosylhomocysteine hydrolase

For a series of acyclic and carbocyclic adenosine analogues, a close correlation was found between their inhibitory effect on murine L929 cell S-adenosylhomocysteine (AdoHcy) hydrolase and their inhibitory effects on the replication of vaccinia virus and vesicular stomatitis virus (r: 0.993 and 0.988, respectively). In terms of their increasing inhibitory action against both virus replication and AdoHcy hydrolase activity the compounds ranked as follows: (S)-9-(2,3-dihydroxypropyl)adenine less than (RS)-3-adenin-9-yl-2-hydroxypropanoic acid (isobutyl ester) less than 3-deazaneplanocin A approximately carbocyclic 3-deazaadenosine less than adenosine dialdehyde less than neplanocin A. These findings point to AdoHcy hydrolase as the target for the antiviral action of these adenosine analogues.