Ambiguous Base Pairing of 1-(2-Deoxy-β-D-Ribofuranosyl)imidazole-4-carboxamide During PCR

Abstract

The use of 5′-triphosphate of 1-(2-deoxy-β-D-ribofuranosyl)imidazole-4-carboxamide (dYTP) in DNA amplification reaction in place of dATP or dGTP yielded mutations frequencies of 3–4×10^?2 per base per amplification. A reasonable proportion of transversions (11–15%) was observed in the absence of deletions and insertions.     

Synthesis of Carbocyclic 1-[4-(Hydroxymethyl)cyclopent-2-enyl]-1,2,4-triazole-3-carboxamide and Its Derivatives

Abstract

The synthesis of carbocyclic 1-[4-(hydroxymethyl)cyclopent-2-enyl]-1,2,4-triazole-3-carboxamide (6a) and its derivatives was achieved from triol 10 in excellent overall yield. This route involves a Pd(0)-catalyzed coupling reaction as a key step.     

SYNTHESIS OF HOMO-N-NUCLEOSIDE WITH 1,2,4-TRIAZOLE-3-CARBOXAMIDE

On the basis of potent biological activities of ribavirin and homo-N-nucleosides, a novel homo-N-1,2,4-triazole-3-carboxamide derivative 1 was synthesized starting from 2,3,5-tri-O-benzoyl-ribofuranosyl-1-acetate as a potential antiviral agent.     

Nucleosides and Nucleotides. 98. Synthesis and Antitumor Activities of 5-Ethynylimidazole-4-carboxamide and -carbonitrile Derivatives

Abstract

5-Ethynyl-1-(2-deoxy-β-D-ribofuranosyl)imidazole-4-carbonitrile (4) and -carboxamide (5) and 5-ethynyl-1-(5-deoxy-β-D-ribofuranosyl)imidazole-4-carbonitrile (11) and -carboxamide (12) have been synthesized from the corresponding 5-iodo derivatives 2 and 7 by a palladium-catalyzed cross-coupling reaction with (tri-methylsilyl)acetylene. The aglycons, 5-ethynylimidazole derivatives 14 and 15 were synthesized by the hydrolytic cleavage of the corresponding nucleosides. The antileukemic activity of these nucleosides and base analogues are also described.     

Synthesis and Biological Activity of 4-Amino-1-(β-D-ribofuranosyl)imidazo[4,5-d]pyridazin-7-one

Abstract

The Lewis acid catalyzed ribosylation of 5(4)-cyano-4(5)-(5-methyl-1,2,4-oxadiazol-3-yl)-1H-imidazole (2) with 1-O-acetyl-2,3,5-tri-O-benzoyl-B-D-ribose gave only 4-(5-methyl-1,2,4-oxadiazol-3-yl)-1-(2,3,5-tri-O-benzoy 1-B-D-ribofuranosyl)imidazole-5-carbonitrile (3). Treatment of 3 with methanolic ammonia gave 4-(5-methyl-1,2,4-oxadiazol-3-yl)-1-(6-D-ribofuranosyl)imidazole-5-carbonitrile (4). Treatment of 4 with hydrogen peroxide in ammonia gave -(5-methyl-1,2,4-oxadiazol-3-yl)-1-(B-D-ribofuranosyl)imidazole-5-carboxamide (5). When 5 was treated with sodium hydride in dimthyl-sulfoxide a rearrangement (mononuclear heterocyclic rearrangement, m.h.r.) occurred to give a modest 17% yield of 4-acetamido-1-(B-D ribofuranosyl)imidazo[4,5-d]pyridazin-7-one (6). Treatment of 6 with aqueous ammonia gave4-amino-l-(B-D-ribofuranosyl)imidazo[4,5-d]pyridazin-7-one (1). The synthesis of compound 1 using the m.h.r. for the preparation of a single regioisomer of the imidazo[4,5-d]pyridazin-7-one ring system, has demonstrated the potential of this methodology. Neither compound 5 nor 6 affected the growth or replication of human foreskin fibroblasts (HFF cells) or human cytomegalovirus (HCMV). In contrast, compound 1 inhibited the replication of HCMV (IC₅₀=29 μM) but produced visual cytotoxicity in uninfected HFF cells (IC₅₀=70μM). Compound 1 also inhibited the proliferation of L1210 murine leukemic cells (IC₅₀=25μM), whereas the precursors 4 and 6 did not.     

Synthesis of 3-Aminoimidazo[4,5-c]pyrazole Nucleoside via the N-N Bond Formation Strategy as a [5:5] Fused Analog of Adenosine

3-Amino-6-(β-D-ribofuranosyl)imidazo[4,5-c]pyrazole (2) was synthesized via an N-N bond formation strategy by a mononuclear heterocyclic rearrangement (MHR). A series of 5-amino-1-(5-O-tert-butyldimethylsilyl-2,3-O-isopropylidene-β-D-ribofuranosyl-4-(1,2,4-oxadiazol-3-yl)imidaz-oles (6a-d), with different substituents at the 5-position of the 1,2,4-oxadiazole, were synthesized from 5-amino-1-(β-D-ribofuranosyl)imidazole-4-carboxamide (AICA Ribose, 3). It was found that 5-amino-1-(5-O-tert-butyldimethylsilyl-2,3-O-isopropylidene-β-D-ribofuranosyl)-4-(5-methyl-1,2,4-oxadiazol-3-yl)imidazole (6a) underwent the MHR with sodium hydride in DMF or DMSO to afford the corresponding 3-acetamidoimidazo[4,5-c]pyrazole nucleoside(s) (7b and/or 7a) in good yields. A direct removal of the acetyl group from 3-acetamidoimidazo[4,5-c]pyrazoles under numerous conditions was unsuccessful. Subsequent protecting group manipulations afforded the desired 3-amino-6-(β-D-ribofuranosyl)imidazo[4,5-c]pyrazole (2) as a 5:5 fused analog of adenosine (1).     

Design and Synthesis of Heterocyclic Carboxamides as Natural Nucleic Acid Base Mimics

Abstract

A series of heterocyclic carboxamides have been designed as mimics for the natural nucleic acid bases. The nucleosides 1-(2′-deoxy-β-d-ribofuranosyl)imidazole-4-carboxamide (1), 1-(2′ -deoxy-β-d-ribofuranosyl)pyrazole-3-carboxamide (2), and 1-(2′ -deoxy-β-d-ribofuranosyl)pyrrole-3-carboxamide (3) were synthesized and their structures confirmed by spectroscopic and analytical means.

     

Synthesis,structure, and antifungal evaluation of some novel 1,2,4-triazolylmercaptoacetylthiosemicarbazide and 1,2,4-triazolylmercaptomethyl-1,3,4-thiadiazole analogs

Novel 1-[[4-(4-bromophenyl)-5-(2-furyl)-4H-1,2,4-triazole-3-yl]mercaptoacetyl]-4-alkyl/aryl-3-thiosemicarbazides (5–12) were synthesized by the reaction of 4-(4-bromophenyl)-5-(2-furyl)-4H-1,2,4-triazole-3-ylmercaptoacetylhydrazide (4) with substituted isothiocyanates. Cyclodehydration of thiosemicarbazides with concentrated sulfuric acid yielded 2-[4-(4-bromophenyl)-5-(2-furyl)-4H-1,2,4-triazole-3-yl]mercaptomethyl-5-alkyl/arylamino-1,3, 4-thiadiazoles (13–17). The new compounds were evaluated for in vitro antifungal activity using the microdilution method. The tested compounds showed varying degrees of activity against Microsporum gypseum NCPF-580, Microsporum canis, Trichophyton mentagrophytes, Trichophyton rubrum, and Candida albicans ATCC 10231 (MIC 8–4 μg/mL).     

Chemoenzymatic method of 1,2,4-triazole nucleoside synthesis: Possibilities and limitations

Possibilities and limitations of chemoenzymatic synthesis of novel structural analogues of an antiviral preparation of Ribavirin (1-β-D-ribofuranosyl-1,2,4-triazole-3-carboxamide) were established. A synthesis of various amides of 1H-1,2,4-triazole-3-carboxylic acid and its 5-substituted analogues—potential substrates of purine nucleoside phosphorylase—has been described. Comparative efficiency of preparation methods of these amides, as well as the methods of introduction of functional groups to the C5 position of heterocyclic system, were investigated. Novel analogues of Ribavirin containing various substitutes in the carboxamide group were synthesized. A biotechnological method was developed for the preparation of 1-β-D-ribofuranozyl-1,2,4-triazole-3-carbonitryl, an intermediate in the synthesis of Viramidine, the modern analogue of Ribavirin.     

Enzymatic Production of Ribavirin from Orotidine by Erwinia carotovora AJ 2992

Microorganisms that produce ribavirin (1-β-d-ribofuranosyl-1,2,4-triazole-3-carboxamide; virazole^®) directly from orotidine and 1,2,4-triazole-3-carboxamide (TCA) were screened from our stock cultures. Of the 425 strains, Erwinia carotovora AJ 2992 was found to possess potent ribavirin-producing ability, from orotidine and TCA. In the presence of intact cells of E. carotovora AJ 2992, 183 mm ribavirin was produced from 300 mm orotidine and 300 mm TCA on 48 hr reaction.     

Synthesis of 2′,3′-Dideoxyribavirin

Abstract

A synthesis of 1-(2,3-dideoxy-β-D-ribofuranosyl)-1,2,4-triazole-3-carboxamide (2′,3′-dideoxyribavirin, ddR) is described. Glycosylation of the sodium salt of 1,2,4-triazole-3-carbonitrile (5) with 1-chloro-2-deoxy-3,5-di-0-p-toluoyl-α-D-erythro-pentofuranose (1) gave exclusively the corresponding N-1 glycosyl derivative with β-anomeric configuration (6), which on ammonolysis provided a convenient synthesis of 2′-deoxyribavirin (7). Similar glycosylation of the sodium salt of methyl 1,2,4-triazole-3-carboxylate (2) with 1 gave a mixture of corresponding N-1 and N-2 glycosyl derivatives (3) and (4), respectively. Ammonolysis of 3 furnished yet another route to 7. A four-step deoxygenation procedure using imidazolylthiocarbonylation of the 3′-hydroxy group of 5′-0-toluoyl derivative (9a) gave ddR (11). The structure of 11 was proven by single crystal X-ray studies. In a preliminary in vitro study ddR was found to be inactive against HIV retrovirus.     

Microbiological synthesis of virazole by immobilized cells]

Based on the isotherms of adsorption of the cells of Xanthomonas campestris B-610 to glass and polyvinyl fibers, immobilized systems were produced, in which the cell content was sufficient for enzymatic synthesis of Virazole (1-[beta-D-ribofuranosyl]-1,2,4-triazole-3-carboxamide) using adenosine as a donor of ribose (50-60% conversion of 1,2,4-triazole-3-carboxamide). The immobilized cells thus obtained retain their enzymatic activity for six months and can be used repeatedly.     

Enzymatic Production of Ribavirin from Pyrimidine Nucleosides by Enterobacter aerogenes AJ 11125

Microorganisms that produce ribavirin(1-β-d-ribofuranosyl-1,2,4-triazole-3-carboxamide; virazole^®) directly from pyrimidine nucleosides and TCA (1,2,4-triazole-3-carboxamide) were screened from our stock cultures. Of the 400 strains tested, 16 were isolated as ribavirin-producers from uridine or cytidine. In particular, Enterobacter aerogenes AJ 11125, Bacillus brevis AJ 1282 and Sarcina lutea AJ 1212 were found to possess potent activities of ribavirin production from them. In the presence of intact cells of Enterobacter aerogenes AJ 11125, which was selected as the best strain, 110.2mm and 67.6 mm ribavirin were produced from uridine and cytidine, respectively, on 96 hr reaction at 60°C. In addition, this strain could also produce ribavirin from guanosine, but could not produce it from orotidine, which is also a pyrimidine nucleoside.     

Nucleosides. II. Synthesis and Properties of 3,4-Diaryl-4,5-dihydro-1-(β-D-ribofuranosyl)-1,2,4-triazole-5-thiones

Abstract

3,4-Diaryl-4,5-dihydro-1,2,4-triazole-5-thiones (1a-c) were silylated to give compounds (2a-c) which were condensed with 1-O-acetyl-2,3,5-tri-O-benzoyl-β-D-ribofuranose (3) in the presence of trimethylsilyl trifluoromethane sulfonate to afford the corresponding nucleosides 4a-c. Treatment of 4a-c with sodium methoxide in methanol at room temperature afforded the debenzoylated nucleosides 5a-c. The reaction of 5a with acetone in the presence of p-toluenesulfonic acid gave the 2′, 3′-isopropylidene derivative (6a). Phosphorylation of 6a with phosphoryl chloride and triethylphosphate followed by treatment with barium hydroxide afforded barium 3,4-diphenyl-4,5-dihydro(β-D-ribofuranosyl)-1,2,4-triazole-5-thione-5′- monophosphate, which gave after lyophilization the free acid (7a)     

Synthesis of some new hybride molecules containing several azole moieties and investigation of their biological activities

1,2,4-Triazole-3-one prepared from tryptamine was converted to the corresponding carbothioamides by several steps. Their treatment with ethyl bromoacetate or 4-chlorophenacyl bromide produced the corresponding 5-oxo-1,3-thiazolidine or 3-(4-chlorophenyl)-1,3-thiazole derivatives. Acetohydrazide derivative that was obtained starting from tryptamine, was converted to the corresponding Schiff basis and sulfonamide by the treatment with suitable aldehydes and benzensulphonyl chloride, respectively. 2-[(4-Amino-5-thioxo-4,5-dihydro-1H-1,2,4-triazole-3-yl)methyl]-4-[2-(1H-indole-3-yl)ethyl]-5-methyl-2,4-dihydro-3H-1,2,4-triazole-3-one was synthesized starting from hydrazide via the formation of the corresponding 1,3,4-oxadiazole compound, while the other bitriazole compounds were obtained by intramolecular cyclisation of carbothioamides in basic media. The treatment of 1,2,4-triazole or 1,3,4-oxadiazole compound with several amines generated the corresponding Mannich bases. Ethyl (2-amino-1,3-thiazole-4-yl)acetate was converted to the corresponding 1,3,4-oxadiazole derivative, arylidenehydrazides, 1,2,4-triazole-3-one and 5-oxo-1,3-oxazolidine derivatives by several steps. The structural assignments of new compounds were based on their elemental analysis and spectral (FT IR, ¹H NMR, ¹³C NMR and LC-MS) data. The antimicrobial, antilipase and antiurease activity studies revealed that some of the synthesized compounds showed antimicrobial, antilipase and/or antiurease activity.     

Compounds similar to acyclovir. VII. Attempts to construct an anti-herpetic agent (6-hydroxy-2-oxa-4-hexenyl derivatives of nucleic bases

Based on the available data on the acyclovir's mechanism of action we attempted to predict the antiherpetic activity of 6-hydroxy-2-oxahexen-4-yl derivatives of nucleic bases. In terms of this model 9-(6-hydroxy-2-oxahexen-4-yl) guanine might be active. 6-Hydroxy-2-oxahexen-4-yl derivatives of adenine, guanine, cytosine, thymine, uracil, 1,2,4-triazole-3 and 1,2,4-triazole-5-carboxamide have been synthesized and their activity against herpes virus I investigated. The guanine derivative proved to possess rather high activity (chemotherapeutical index 8).     

An Unusual Iodine Monochloride Chlorination of an Imidazole Nucleoside

Abstract

The reaction of iodine monochloride with the imidazole nucleoside, 5-amino-1-(2,3,5-tri-0-acetyl-α-D-ribofuranosyl)imidazole-4-carboxamide, provides the 2-chloroimidazole nucleoside in good yield.     

Synthesis and antiviral activity of amino acid esters of ribavirin

The synthesis and antiviral activity of amino acid esters of 1-(β-D-ribofuranosyl)-1,2,4-triazole-3-carboxamide (ribavirin,1) is described.     

Oligodeoxynucleotides Embodying the Ambiguous Base Z, 5-Amino-imidazole-4-carboxamide

Abstract

Short oligomers containing 5-amino-1-(2-deoxy-β-D-ribofuranosyl)imidazole-4-carboxamide (dZ) were synthesized in solution using the phosphotriester methodology. Usual acyl groups were used for the canonical bases. For the exocyclic amino function of Z residue, the hydrogenolyzable benzyloxycarbonyl group was introduced.     

The broad spectrum antiviral agent ribavirin inhibits capping of mRNA.

Ribavirin (1-β-D-ribofuranosyl-1,2,4-triazole-3-carboxamide) is a broad spectrum antiviral substance active against a wide range of both DNA and RNA viruses. It is, however, virtually inactive against polio virus. Its pharmacological mechanism of action was obscure. A possible common target for a chemotherapeutic agent in both DNA and RNA viruses is the “capping” reaction of mRNAs which $\text{inter}\text{alia}$ involves the formation of a guanine pyrophosphate structure at the 5′ terminus by mRNA guanylyl transferase. We have observed that Ribavirin triphosphate is a potent competitive inhibitor of the capping guanylation of viral mRNA. This finding could account for the antiviral potency of the drug against both DNA and RNA viruses and its ineffectiveness against a virus in which the mRNAs derived from them are not capped.