Design, synthesis, and antiviral evaluation of 2-deoxy-D-ribosides of substituted benzimidazoles as potential agents for human cytomegalovirus infections

Stereoselective glycosylation of 2,5,6-trichlorobenzimidazole (1b), 2-bromo-5,6-dichlorobenzimidazole (1c), 5,6-dichlorobenzimidazole (1d), 5,6-dichlorobenzimidazole-2-thione (1e), 5,6-dichloro-2-(methylthio)benzimidazole (1f), 2-(benzylthio)-5,6-dichlorobenzimidazole (1g), and 2-chloro-5,6-dimethylbenzimidazole (1h) with 2-deoxy-3,5-di-O-p-toluoyl-alpha-D-erythro-pentofuranosyl chloride was achieved to give the desired beta nucleosides 2b-h. Subsequent deprotection afforded the corresponding free beta-D-2-deoxyribosides 3b-h. The 2-methoxy derivative 3i was synthesized by the treatment of 2b with methanolic sodium methoxide. Displacement of the 2-chloro group of 2b with lithium azide followed by a removal of the protective groups gave the 2-azido-5,6-dichlorobenzimidazole derivative (5). The 2-amino derivative (6) was obtained by hydrogenolysis of 5 over Raney nickel. 5,6-Dichloro-2-isopropylamino-1-(2-deoxy-beta-D-erythro- pentofuranosyl)benzimidazole (10) was prepared using 2'-deoxyuridine (7), N-deoxyribofuranosyl transferase and 1d followed by functionalization of the C2 position. Antiviral evaluation of target compounds established that compounds 3b and 3c were active against human cytomegalovirus (HCMV) at non-cytotoxic concentrations. The activity of these 2-deoxy ribosides, however, was less than the activity of the parent riboside, 2,5,6-trichloro-1-beta-D-ribofuranosylbenzimidazole (TCRB). Compared to TCRB, 3b and 3c were somewhat more cytotoxic and active against herpes simplex virus type 1. Compounds 3d-i with other substituents in the 2-position were inactive against both viruses and non-cytotoxic. In contrast, compounds with amine substituents in the 2-position (5, 6, 10) were active against HCMV albeit less so than TCRB. These results establish that 2-deoxy-D-ribosyl benzimidazoles are less active against the DNA virus HCMV than are the corresponding D-ribosides.     

Design,Synthesis and Antiviral Activity of α-L-Arabinofuranosyl Derivatives of 2-Substituted-5,6-dichlorobenzimidazoles

Abstract

A number of 2-substituted-5,6-dichloro-l-(α-L-arabinofuranosyl)benzimidazoles have been prepared by condensation of 2-bromo-5,6-dichlorobenzimidazole or 2,5,6-trichlorobenzimidazole with tetra-O-acetyl-L-arabinofuranose. 2-Alkylamino derivatives were prepared by a substitution of the 2-chloro group with the appropriate amines. All target compounds were evaluated for activity against HCMV and HSV-1. The 2-chloro and 2-bromo derivatives showed moderate activity against HCMV at non-cytotoxic concentrations.     

Design,Synthesis, and Antiviral Evaluation of Some Polyhalogenated Indole C-nucleosides

2,5,6-Trichloro-1-(β-D-ribofuranosyl)benzimidazole (TCRB), 2-bromo-5,6-dichloro-1-(β-D-ribofuranosyl)benzimidazole (BDCRB) and 2-benzylthio-5,6-dichloro-1-(β-D-ribofuranosyl)benzimidazole (BTDCRB) are benzimidazole nucleosides that exhibit strong and selective anti-HCMV activity. Polyhalogenated indole C-nucleosides were prepared as 1-deaza analogs of the benzimidazole nucleosides TCRB and BDCRB. A mild Knoevenagel coupling reaction between an indol-2-thione and a ribofuranose derivative was developed for the synthesis of 2-benzylthio-5,6-dichloro-3-(β-D-ribofuranosyl)indole (12). 3-(β-D-ribofuranosyl)-2,5,6-trichloroindole (16) was prepared from 12 in 4 steps. A Lewis acid-mediated glycosylation method was then developed to prepare the targeted 2-haloindole C-nucleoside 16 stereoselectively in four steps from the corresponding 2-haloindole aglycons. Only 12 was active against HCMV but it also was somewhat cytotoxic.     

Synthesis and Biological Evaluation of Some 5-Nitro- and 5-Amino Derivatives of 2′-Deoxycytidine, 2′,3′-Dideoxyuridine,and 2′,3′-Dideoxycytidine

Abstract

In this article, we describe the synthesis of 5-nitro-1-(2-deoxy-α-D-erythro-pentofuranosyl)cytosine (4α), 5-nitro-1-(2-deoxy-β-D-erythro-pentofuranosyl)cytosine (4β), 5-amino-1-(2-deoxy-α-D-erythro-pentofuranosyl)cytosine (5α), 5-nitro-1- (2-deoxy-β-D-erythro-pentofuranosyl)cytosine (5β), 5-nitro-1-(2,3-dideoxy-β- D-ribofuranosyl)uracil (6β), 5-amino-1-(2,3-dideoxy-α,β-D-ribofuranosyl)uracil (7), 5-nitro-1-(2,3-dideoxy-α,β-D-ribofuranosyl)cytosine (8) and 5-amino-1-(2,3-dideoxy-β-D-ribofuranosyl)cytosine (9β). The prepared compounds were tested for their activity against HIV and HBV viruses, but they did not show significant activity.     

Synthesis of New 5″-Sulfonylamido Derivatives of 3″-Azido-3″-Deoxythymidine (AZT)

Abstract

A series of 5′-N-methanesulfonyl derivatives of 3′-azido-5′-(alkylamino)-3′,5′-dideoxythymidine was synthesised. The first step of the synthesis involved the reaction of 1-(2,5-dideoxy-5-O-tosyl-β-D-threo-pentofuranosyl)thymine 1 with an appropriate amine to give 1-[5-(alkylamino)-2,5-dideoxy-β-D-threo-pentofuranosyl]thymines 2a-e and 1-(2,5-dideoxy-β-threo-pent-4-enofuranosyl)thymine 3 as a by-product. Compounds 2a-e were treated with an excess of methanesulfonyl chloride to yield intermediates 1-[5-(dimethylamino)-3-O-methanesulfonyl-2,3,5-trideoxy-β-D-threo-pentofuranosyl]-thymine 4a and 1-[5-(N-alkyl-N-methanesulfonyl)-3-O-methanesulfonyl-2,3,5-trideoxy-β-D-threo-penfuranosyl]thymines 4b-e. The reaction of 4a-e with lithium azide in dimethyl-formamide afforded the final compounds 1-[3-azido-5-(N-methyl-N-methanesulfonyl)-2,3,5-trideoxy-β-D-erythro-penofuranosyl]thymine 5a and 1-[3-azido-5-(N-alkyl-N-methanesulfonyl)-2,3,5-trideoxy-β-D-erythro-penofuranosyl]thymines 5b-e. The independent synthesis of 4′,5′-unsaturated product 3 was also described.     

Stereoselective Synthesis of 6-Methyl-9-(2-Deoxy-β-D-Erythro-Pentofuranosyl)purine

Abstract

The coupling of the sodium salt of 6-methylpurine with 2-deoxy-3,5-di-O-p-toluoyl-α-D-erythro-pentofuranosyl chloride in acetonitrile gives the di -O-p-toluoyl protected 9-β nucleoside regio- and stereo-selectively in good yield. Methoxide deprotection followed by preparative hplc then affords pure 6-methyl-9-(2-deoxy-β-D-erythro-pentofuranosyl)purine.     

Nucleosides and Nucleotides. 106. Synthesis and Biological Activity of 1-(2-Deoxy-2-hydroxyimino- or Methoxyimino-β-D-erythro-pentofuranosyl)-thymine and -Cytosine§,1

Abstract

Reaction of 1-(3,5-Otetraisopropyldisiloxan-1,3-diyl-β-D-erythro-2-pentofuran-2-ulosyl)uracil (8) with hydroxylamine hydrochloride in pyridine at room temperature for 24 h or at 80°C for 3 h gives the 2′-deoxy-2′-hydroxyiminouridine derivative 9 in good yield. Similarly, oximation of 8 with methoxyamine has been done to obtain 2′-deoxy-2′-methoxyimino derivatives 11 in a high yield. Compound 9 was converted into 1-(2-deoxy-2-hydroxyimino-β-D-erythro-pentofuranosyl)cytosine (3). Cytotoxicity in vitro of these nucleosides against murine leukemia L1210 cells was also examined.     

Isomérisation des 5-bromo-5,6-dihydro-6-hydroxythymidines. Préparation des formes anomères de la thymidine et de la 1-(2-désoxy-D-érythro-pentofuranosyl)thymine

The trans 5-(R), 6-(R) and 5-(S), 6-(S) diastereoisomeric forms of 5-bromo-5,6-dihydro-6-hydroxythymidine were obtained by the action of bromine upon thymidine in aqueous solution. Treatment of these compounds with warm M hydrobromic acid both rearranges the sugar moiety and cleaves the glycosylamine bond; the yields of both processes were determined. Reduction of the halohydrins gave three isomeric compounds derived from thymidine : 1-(2-deoxy-α-D-erythro-pentofuranosyl)thymine, 1-(2-deoxy-β-D-erythro-pentopyranosyl)thymine and 1-(2-deoxy-α-D-erythro-pentopyranosyl)thymine. These isomerisations were also shown in the treatment of thymidine with hydrobromic acid, but, in the latter case, the process is less productive than in the former one. A mechanism for these reactions is discussed.     

Synthesis of N-1β-D-Arabinofuranosyl and N-1-2′-Deoxy-β-D-erythro-pentofuranosyl Thieno [3,2-d] Pyrimidine Nucleosides

Abstract

Synthetic methods for 1-(β-D-arabinofuranosyl) and 1-(2-deoxy-β-D-erythro-pentofuranosyl)thieno[3,2-d]pyrimidine-2,4-diones from the orresponding 1-(β-D-ribofuranosyl) nucleoside have been developed in this report. These compounds were tested against HIV-1 in CEM cl 13 cell cultures, but none of them exhibited significant inhibitory activity against this virus.     

Synthesis and Structural Analysis of Oxadiazole Carboxamide Deoxyribonucleoside Analogs

Two novel C-linked oxadiazole carboxamide nucleosides 5-(2′-deoxy-3′,5′-β-D-erythro-pentofuranosyl)-1,2,4-oxadiazole-5-carboxamide (1) and 5-(2′-deoxy-3′,5′-β-D-erythro-pentofuranosyl)-1,2,4-oxadiazole-3-carboxamide (2) were successfully synthesized and characterized by X-ray crystallography. The crystallographic analysis shows that both unnatural nucleoside analogs 1 and 2 adapt the C2′-endo (“south”) conformation. The orientation of the oxadiazole carboxamide nucleobase moiety was determined as anti (conformer A) and high anti (conformer B) in the case of the nucleoside analog 1 whereas the syn conformation is adapted by the unnatural nucleoside 2. Furthermore, nucleoside analogs 1 and 2 were converted with high efficiency to corresponding nucleoside triphosphates through the combination chemo-enzymatic approach. Oxadiazole carboxamide deoxyribonucleoside analogs represent valuable tools to study DNA polymerase recognition, fidelity of nucleotide incorporation, and extension.

     

8-Aza-1-deazapurine Nucleosides as Antiviral Agents

Abstract

2′,3′-Dideoxy-8-aza-1-deazaadenosine (21) and its α-anomer (20) were synthesized via glycosylation of 7-chloro-3H-1,2,3-triazolo[4,5-b]pyridi-ne with 2,3-dideoxy-5-O-[(1, 1)-dimethylethyl)diphenylsilyl]-D-glycero-o-pen-tofuranosyl chloride. The reaction gave a mixture of α- and β-anomers of N³-, N⁴- and N¹-glycosylated regioisorners (12–15). The α- and β-anomers of the N⁴-glycosylated isomer 26 and 27 were also synthesized through the glycosylation of 8-aza-1-deazaadenine with 1-acetoxy-2,3-dideoxy-5-O-f(1,1-di-methylethyl)dimethylsilyl]-D-glycero-pentouranose. These dideoxynucleo-sides and a series of previously synthesized 8-aza-1-deazapurine nucleosidcs were tested for activity against several DNA and RNA viruses, HIV-1 included. The α- and β-anomers of 7-chloro-3-(2-deoxy-D-erythro-pentofuranosyl)-3H-1,2,3-triazolo[4,5-b]pyridine (3a and 4) showed activities against Sb-1 and Coxs viruses. The α- and β-anomers of 2′,3′-dideoxy-8-aza-1-deazaadenosine (20 and 21) were found active as inhibitors of adenosine deaminase.     

Convenient Syntheses of 6-Methylpurine and Related Nucleosides

Abstract

Efficient methods for the synthesis of 6-methylpurine (3), 9-(2-deoxy-β-D-erythro-pentofuranosyl)-6-methylpurine (8), and 6-methyl-9-β-D-ribofuranosylpurine (5) are described. Methodology involving the (Ph₃P)₄Pd catalyzed cross-coupling reaction of CH₃ZnBr with several different 6-chloropurine derivatives is described in high yield. This methodology now provides a facile and high-yielding synthesis of 8, which is needed in significant amounts for studies in cancer gene therapy.     

Design, synthesis, and antiviral evaluation of some polyhalogenated indole C-nucleosides

2,5, 6-Trichloro-1-(beta-D-ribofuranosyl)benzimidazole (TCRB), 2-bromo-5, 6-dichloro-1-(beta-D-ribofuranosyl)benzimidazole (BDCRB) and 2-benzylthio-5,6-dichloro-1-(beta-D-ribofuranosyl)benzimidazole (BTDCRB) are benzimidazole nucleosides that exhibit strong and selective anti-HCMV activity. Polyhalogenated indole C-nucleosides were prepared as 1-deaza analogs of the benzimidazole nucleosides TCRB and BDCRB. A mild Knoevenagel coupling reaction between an indol-2-thione and a ribofuranose derivative was developed for the synthesis of 2-benzylthio-5, 6-dichloro-3-(beta-D-ribofuranosyl)indole (12). 3-(beta-D-ribofuranosyl)-2,5,6-trichloroindole (16) was prepared from 12 in 4 steps. A Lewis acid-mediated glycosylation method was then developed to prepare the targeted 2-haloindole C-nucleoside 16 stereoselectively in four steps from the corresponding 2-haloindole aglycons. Only 12 was active against HCMV but it also was somewhat cytotoxic.     

Chemo-enzymatic Synthesis of 3-Deoxy-β-D-ribofuranosyl Purines and Study of Their Biological Properties

Abstract

9-(3-Deoxy-β-d-erythro-pentofuranosyl)-2,6-diaminopurine (2) was synthesized by an enzymatic transglycosylation of 2,6-diaminopurine using 3′-deoxycytidine (1) as a donor of the sugar moiety. Nucleoside 2 was transformed to 3′-deoxy guanosine (3), 9-(3-deoxy-β-d-erythro-pentofuranosyl)-2-amino-6-oxopurine (3′-deoxyisoguanosine; 4), and 9-(3-deoxy-β-d-erythro-pentofuranosyl)-2-fluoroadenine (5). Compounds 2–5 were evaluated for their anti-HIV activity.     

Synthesis of a Novel C-Nucleoside, 2-Amino-7-(2-deoxy-β- D-erythro-pentofuranosyl)-3H,5H-pyrrolo-[3,2-d]pyrimidin-4-one (2′-Deoxy-9-deazaguanosine)

Abstract

A synthesis of the C-nucleoside, 2-amino-7-(2-deoxy-β-D-erythro-pentofuranosyl)-3H,5H-pyrrolo[3,2-d]pyrimidin-4-one (9-deaza-2′-deoxyguanosine) was achieved starting from 2-amino-6-metnyl-3H-pyrimidin-4-one (5) and methyl 2-deoxy-3,5-di-O-(p-nitrobenzoyl)- D-erythro-pento-furanoside (11). The anomeric configuration of the C-nucleoside was established by ¹H NMR, NOEDS and ROESY. This C-nucleoside did not inhibit the growth of T-cell lymphoma cells.     

Formation of an Unexpected 2-Deoxy-α-D-Threo-Pentofuranosyl Azide by Reaction of O2,3′-Anhydro-5′-O-trityl-2′-deoxycytidine with Lithium Azide

Abstract

Reaction of 0²,3′-anhydro-5′-0-trityl-2′-deoxycytidine (1) with LiN₃s in DMF resulted in the formation of 1-(3-azido-2,3-dideoxy-5-0-trityl-β-D-erythro-pentofuranosyl) cytosine (2) and 3-0-(4-amino-1,3-pyrimidin-2-yl)-5-0-trityl-2-deoxy-α-D-threo-pentofuranosyl azide (3) (2:3 = 1:1) in 88% yield. Compound 3 was deprotected with 80% aqueous AcOH yielding 4     

Synthesis of a C-nucleoside analog of the antibiotic cordycepin

A C-nucleoside analog of cordycepin, 6-amino-8-(3-deoxy-β-D-erythro-pentofuranosyl)purine (6), has been synthesized. 3-Deoxy-2,5-di-O-(p-nitrobenzoyl)- β-D-erythro-pentofuranosyl bromide reacted with mercuric cyanide in nitromethane to give 2,5-anhydro-4-deoxy-3,6-di-O-(p-nitrobenzoyl)-D-ribo-hexononitrile which, after acid hydrolysis and removal of the protecting groups, afforded 2,5-anhydro-4-deoxy-D-ribo-hexonic acid. Reaction of this acid with 4,5,6-triaminopyrimidine gave the corresponding amide, which was pyrolyzed to give compound 6. The mass- and n.m.r.-spectral data for the synthesized analog are quite similar to those of the natural antibiotic.     

6-Azathymidine-4′-thionucleosides: synthesis and antiviral evaluation

The synthesis of dideoxy-6-azathymidine 4′-thionucleoside 1-(2,3-dideoxy-4-thio-β-D-erythro-pentofuranosyl)-(6-azathymidine) (2), and the L-nucleoside, 1-(4-thio-β-L-erythro-pentofuranosyl)-(6-azathymidine) (3) and their evaluation against a wide panel of antiviral assays are described. The L-thionucleoside (3) was devoid of antiviral activity. The dideoxy-thionucleoside (2) was moderately active against vaccinia virus (VV) and the herpes simplex virus strains HSV-1 (strain KOS) and HSV-2 (strain G) (MIC 12 μM) and retained inhibitory activity vs a thymidine kinase-deficient strain HSV-1/TK^–, suggesting that (2) is not dependent on viral TK-catalysed phosphorylation for antiviral activity and/or may use an alternative metabolic activation pathway.     

8-Aza Analogues of Deaza Purine Nucleosides. Synthesis and Biological Evaluation of 8-Aza-1-deazaadenosine and 2′-Deoxy-8-aza-1-deazaadenosine

Abstract

The syntheses of 7-amino-3-(β-D-ribofuranosyl)-3H-1,2,3-triazolo[4,5-b]pyridine (8-aza-1-deazaadenosine) (2) and 7-amino-3-(2-deoxy-β-D-erythro-pentofuranosyl)-3H-1,2,3-triazolo[4,5-b]pyridine (2′-deoxy-8-aza-1-deazaadenosine) (3) by glycosylation of the anion of 7-chloro-3H-1,2,3-triazolo[4,5-b]pyridine are described. The anomeric configuration as well as the position of glycosylation were determined by ¹H, ¹³ NMR, UV and N.O.E. difference spectroscopy. The cytotoxicity of these nucleosides against several murine and human tumor cell lines is discussed. Compounds 2 and 3 proved to be good inhibitors of adenosine deaminase.     

Studies Designed to Increase the Stability and Antiviral Activity (HCMV) of the Active Benzimidazole Nucleoside,TCRB

Abstract

The potent activity of 2,5,6-trichloro-1-(ß-D-ribofuranosyl)benzimidazole (TCRB) against Human Cytomegalovirus with the concomitant low cellular toxicity at concentrations that inhibit viral growth prompted considerable interest in this research area. This interest was moderated by the pharmacokinetic studies of TCRB in rats and monkeys that revealed the instability of TCRB in vivo. These studies suggested that the instability was due to a cleavage of the glycosidic bond in vivo which released the heterocycle (2,5,6-trichlorobenzimidazole) into the bloodstream. This prompted us to initiate synthetic studies designed to increase the stability of the glycosidic bond of TCRB and BDCRB. Several synthetic approaches to address this and other problems are presented.