Nucleosides. 1. 9-(3'-Alkyl-3'-deoxy-beta-D-ribofuranosyl)adenines as lipophilic analogues of cordycepin. Synthesis and preliminary biological studies.

A series of lipophilic 9-(3'-alkyl-3'-deoxy-beta-D-ribofuranosyl)adenines of increasing chain length was synthesized from the corresponding branched sugars via titanium chloride catalyzed ribosylation of chloromercuri-6-benzamidopurine. Enhanced growth inhibitory activity was observed against (CCRF-CEM human lymphoblastic leukemia cells in culture as the length of the alkyl side chain in the sugar and the resultant lipophilic character of the nucleoside were increased. Experiments involving incorporation of radiolabeled uridine, thymidine, and leucine revealed that in contrast to cordycepin (1) the 3'-n-butyl and 3'-n-hexyl analogues 5 and 6 markedly inhibit not only RNA synthesis but DNA and protein synthesis as well.     

9-{[3-fluoro-2-(hydroxymethyl)cyclopropylidene]methyl}adenines and -guanines. Synthesis and antiviral activity of all stereoisomers1

All stereoisomers of adenine and guanine methylene-3-fluoromethylenecyclopropane analogues of nucleosides 9a, 9b, 10a, 10b, 11a, 11b, 12a, and 12b were synthesized and their antiviral activities were evaluated. A highly convergent approach permitted the synthesis of all these analogues using a single intermediate 15. Reaction of aldehyde 13 with fluorotrichloromethane and tri-n-butylphosphine gave fluoroalkenes 14a+14b (83:17). Addition of carbene derived from ethyl diazoacetate gave cyclopropane 15 as the major product. Reduction (19), bromination (20), and phenylselenenylation (21), followed by Se oxidation and beta-elimination gave cis-methylenecyclopropane 22. Addition of bromine provided the reagent 23 for alkylation-elimination. Reaction of 23 with adenine led to an isomeric mixture 25a+26a that after deprotection afforded analogues 9a and 10a. The 2-amino-6-chloropurine furnished 25e+26e and after deblocking (9e and 10e) and hydrolysis gave targets 9b and 10b. Intermediate 15 provided, after debenzylation (27), 2-nitrophenylselenenylation (28), reduction (29), benzylation (30), and oxidation-elimination trans-methylenecyclopropane 31. Addition of bromine gave reagent 32. Further transformations followed the sequence outlined for analogues 9a, 9b, 10a, and 10b. Analogue 9b was effective against human cytomegalovirus (HCMV; Towne) with EC50 2.9 microM. The trans-isomer 10b inhibited AD169 strain of HCMV (EC50 15 microM) and the murine virus MCMV (EC50 2.5 microM). Compound 12a was effective against Epstein-Barr virus (EC50<0.03 microM). Analogue 9a inhibited varicella zoster virus (EC50 5.9 microM) and human immunodeficiency virus type 1 (EC50 5.2 microM). Analogues 9a, 10a, and 11a are moderate substrates for adenosine deaminase. The structure-activity relationships will be discussed in context with other methylenecyclopropane analogues.     

Synthesis and antiviral activity of 9-alkoxypurines. 1. 9-(3-Hydroxypropoxy)- and 9-[3-hydroxymethyl)propoxy]purines

Reaction of hydroxyl-protected derivatives of hydroxyalkoxyamines (3a,b,c) with either 4,6-dichloro-2,5-diformamidopyrimidine (5) or 4,6-dichloro-5-formamidopyrimidine (31) and subsequent cyclization of the resultant 6-(alkoxyamino)pyrimidines (6, 17, 32, 35) by heating with diethoxymethyl acetate afforded 9-alkoxy-6-chloropurines (7, 18, 33, 36), which were converted subsequently to 9-(3-hydroxypropoxy)- and 9-[3-hydroxy-2-(hydroxymethyl)propoxy] derivatives of guanine, 2-amino-6-chloropurine, 2-amino-6-alkoxypurines, 2-aminopurine, 2,6-diaminopurine, adenine, hypoxanthine, and 6-methoxypurine (8, 12, 13, 19-21, 23-26, 34, 37-39). Carboxylic acid esters (9-11, 14-16, 27-29) and a cyclic phosphate derivative (22) of the 9-(hydroxyalkoxy)guanines (8, 21) and 2-amino-9-(hydroxyalkoxy)purines (13, 26) were also prepared. The guanine derivatives (8, 21) showed potent and selective activity against herpes simplex virus types 1 and 2 and varicella zoster virus in cell cultures and 8 is more active than acyclovir. Although without significant antiviral activity in cell cultures, the 2-aminopurines (13, 14-16, 26-29) and 2-amino-6-alkoxypurines (12, 23-25) are well absorbed after oral administration to mice and are converted efficiently to the antiviral guanine derivatives (8, 21) in vivo.     

Synthesis and antiviral activity of 3'-C-cyano-3'-deoxynucleosides

A series of 3'-C-cyano-3'-deoxynucleosides have been synthesized and evaluated as antiviral agents. Reaction of 2',5'-bis-O-(tert-butyldimethylsilyl)-beta-D-erythro-pentofuranos- 3'-ulosyl derivatives of uracil, 4-N-acetylcytosine, and adenine with sodium cyanide gave a mixture of epimeric cyanohydrins, which after 3'-deoxygenation yielded the corresponding 3'-C-cyano-3'-deoxy-beta-D-xylo-pentofuranosyl derivatives 10. These compounds were epimerized to the corresponding beta-D-ribo-pentofuranosyl derivatives 11. Desilylation of 10 and 11 gave the deprotected 3'-C-cyano-3'-deoxy-beta-D-xylo- and -ribo-pentofuranosyl nucleosides. These derivatives of uridine, cytidine, and adenine, as well as the 3'-C-cyano-3'-deoxy-beta-D-xylo- and -ribo-pentofuranosyl, 3'-C-cyano-2',3'-dideoxy-beta-D-threo- and -erythro-pentofuranosyl, and 3'-C-cyano-2',3'-dideoxy-beta-D-glycero-pent-2'-enofuranosyl derivatives of thymine, were evaluated for their antiviral activity. None of the compounds proved active against the replication of retroviruses (human immunodeficiency virus, murine sarcoma virus) at concentrations that were not toxic to the host cells. However, the 3'-C-cyano-3'-deoxy-beta-D-xylo- (12e) and -ribo-pentofuranosyl (13e) derivatives of adenine showed activity against some DNA (i.e., vaccinia) and RNA (i.e., Sindbis, Semliki forest) viruses at concentrations well below the cytotoxicity threshold.     

Synthesis and antiviral activity of 9-alkoxypurines. 2. 9-(2,3-Dihydroxypropoxy)-, 9-(3,4-dihydroxybutoxy)-, and 9-(1,4-dihydroxybut-2-oxy)purines.

Reaction of alkenoxyamines (3,5) or (R,S)-, (R)-, and (S)-hydroxy-protected derivatives of hydroxyalkoxyamines (20a,b, 37a-c) with 4,6-dichloro-2,5-diformamidopyrimidine (4) and cyclization of the resultant 6-[(alkenoxy)amino]-and 6-(alkoxyamino)pyrimidines (6,7,21a,b, 38a,b,c) by heating with diethoxymethyl acetate afforded 9-alkenoxy- and 9-alkoxy-6-chloropurines (9,10,22a,b, 39a-c, 40a). These were subsequently converted to 9-(2,3-dihydroxypropoxy), 9-(3,4-dihydroxybutoxy), and 9-(1,4-dihydroxybut-2-oxy) derivatives of guanine and 2-aminopurine (13-16, 25-28, 41a-c, 42a). A 2-amino-6-methoxypurine derivative (17) was also prepared. The racemic guanine derivative 13 showed potent and selective activity against herpes simplex virus types 1 and 2 (HSV-1 and HSV-2), but was less active against varicella zoster virus (VZV). Its antiviral activity is attributable to the S isomer (28), which was found to be more active than acyclovir against HSV-1 and HSV-2 and about 4 times less active than acyclovir against VZV. The S enantiomer of 9-(1,4-dihydroxybut-2-oxy)guanine (41c) also showed noteworthy antiviral activity in cell culture. Although this acyclonucleoside (41c) is only weakly active against HSV-1 and inactive against HSV-2, it is about twice as active as acyclovir against VZV.     

Synthesis of some glycoside analogs and related compounds from 9-amino-6-(methylthio)-9H-purine.

Additional information on the anticancer activity of 9-amino-9H-purine-6(1H)-thione and its derivatives was sought by the synthesis of some 9-(substituted amino)-6-(methylthio)-9H-purines in which the 9-substituent contained functional groups capable of either reversible or irreversible binding with an enzymatic site. Condensation of 9-amino-6-(methylthio)-9H-purine (1) with some carbonyl compounds followed by hydride reduction of the azomethine linkage in the intermediates leads to the 2-pyrrolylmethyl (8), 2,3,4-trihydroxybutyl (10), and the 1,5-dihydroxy-2- and 3-pentyl (11 and 12) compounds. A 4-hydroxybutyl derivative (13) was obtained by alkylation of 18, the 9-acetyl derivative of 1, with 4-chlorobutyl acetate followed by saponification. The cyclization of 13 and 11 with a sulfonyl chloride gave the 9-pyrrolidin-1-yl (27) and the 9-[2-(tosyloxymethyl)pyrrolidin-1-yl] (28), respectively. Acylation of 1 with ethyl L-2-pyrrolidine-5-carboxylate and ethyl 1-methyl-5-pyrrolidone-3-carboxylate, respectively, in Me2SO containing NaH gave the corresponding amides 15 and 17. Alkylation of 18 with 1-bromo-2-chloroethane and epichlorohydrin gave the N-(2-chloroethyl) and N-(1,2-epoxy-3-propyl) derivatives 19 and 20. The chloro group of the chlorobutyl derivative of 18 was displaced with KSCN and NaN3, respectively, to give the thiocyanate and azido derivatives 23 and 24. Hydrogenation of the latter gave the amine (25), which was acylated with ethyl chloroformate to give the (ethoxycarbonyl)amino compound 26. None of these compounds showed activity against L1210 leukemia cells implanted ip in mice on a single-dose schedule, suggesting that the activity observed in the simpler 9-aminopurines resulted from cleavage of the hydrazino linkage to give pH-purine-6(1H)-thione.     

Induction and inhibition of the in vitro N1-oxidation of 9-benzyladenine and isomeric 9-(nitrobenzyl)adenines

The present study investigated some aspects of the enzymology of the in vitro N1-oxidation of 9-benzyladenine (BA) and isomeric 9-(nitrobenzyl)adenines (NBAs) using various potential inducers and inhibitors of cytochrome P-450 (CYP). When incubated with phenobarbital-induced rabbit hepatic microsomes, the N1-oxidation rates of BA and 9-(4-nitrobenzyl)adenine were about 6- and 2-fold higher than that of the control, respectively; while the N1-oxidation of 9-(2-nitrobenzyl)adenine and 9-(3-nitrobenzyl)adenine was not markedly affected. In contrast, beta-naphthoflavone and Arochlor 1254 showed no inductive effects towards the N1-oxidation of any of these substrates. Using 12 typical CYP inhibitors, it was found that nifedipine (CYP3A inhibitor) and haloperidol (CYP2D inhibitor) showed significant inhibition towards the N1-oxidation of BA and NBAs. Therefore, the N1-oxidation of BA and NBAs is probably catalysed by CYP3A and CYP2D subfamilies. Furthermore, when 9-(4-nitrobenzyl)adenine was incubated with compounds which possessed a certain chemical similarity to the adenine substrate, various degrees of inhibition of N1-oxidation of 9-(4-nitrobenzyl)adenine were observed. These observations allowed a preliminary indication as to the structure-metabolism relationship of 9-substituted adenine derivatives.     

4（R）—（6—氨基—9—嘌呤基）—2（R）—（羟甲基）四氢呋喃—3（R）—醇的合成

为寻找抗免疫缺陷病毒化合物,以D－核糖为原料,经甲基化、硅烷基化、还原裂解反应制得重要中间体1－脱氧核糖（5）,再通过形成环状亚砜化合物,与NaN3发生反应后,经过还原、缩合、环合、氨化、脱保护基反应制得异脱氧腺嘌呤核苷（1）,各步反应收率均超过70％。     

Synthesis and antirhinovirus activity of 8-substituted analogues of 6-(dimethylamino)-9-(4-methylbenzyl)-2-(trifluoromethyl)-9H-purine.

Several 8-substituted analogues of 6-(dimethylamino) -9-(4-methylbenzyl)-2-(trifluoromethyl)-9H-purine (1) were synthesized and tested for activity against rhinovirus type 1B. Among 16 8-substituted analogues, the 8-amino (3) and 8-bromo (2) analogues were most active with IC50s of 0.36 and 1.4 microM, respectively, under conditions where 1 had an IC50 of 0.03 microM.     

Synthesis and antirhinovirus activity of 6-(dimethylamino)-2-(trifluoromethyl)-9-(substituted benzyl)-9H-purines

A series of 6-(dimethylamino)-2-(trifluoromethyl)-9-(substituted benzyl)purines was synthesized and tested for antirhinovirus activity. Most of the compounds were synthesized by alkylation of 6-chloro-2-(trifluoromethyl)-9H-purine with the appropriate benzyl halide followed by displacement of the chloro group with dimethylamine. Alternatively, 6-(dimethylamino)-2-(trifluoromethyl)purine was alkylated with the appropriate benzyl halide. Although several different aryl substituents provided compounds with IC50's = 0.03 microM against rhinovirus serotype 1B, no congener was significantly more active than the parent 2. Twenty-three compounds were tested against 18 other serotypes, but none exhibited a uniform profile of activity.     

Synthesis of 5'-N-(alpha-amino-beta-mercaptoacyl)amino-5'-deoxynucleosides as potential antiviral compounds.

5'-N-(alpha-Amino-beta-mercaptoacyl)amino-5'-deoxynucleosides have been synthesized by coupling of N-formylthiazolidines derived from D- and L-penicillamine, and D- and L-cysteine to 5'-amino-5'-deoxynucleosides using the DCC/HOSu method, followed by deprotection in N HCl in MeOH under argon. Although these compounds were designed as potential anti-HIV-1 agents, none of them showed anti-HIV-1 activity in MT-4 cells or antiviral effect against some other viruses, at concentrations below the cytotoxicity threshold.