A Convenient Synthesis of D-Psicofuranosyl Nucleosides1

Abstract

As part of our studies on the synthesis of conformationally restricted nucleosides of types 1 and 2, where X = CH₂, O or S, we required access to differentially substituted D-psicofuranosyl nucleosides such as 3. As shown in the table, we have developed a convenient approach to such compounds that depends on the direct condensation of the 1,2:3,4-di-O-isopropylidene-β-D-psicofuranose derivative 4 with an appropriate silylated purine or pyrimidine base.² Although the α and β anomers of 3 are formed in a 1:1 ratio, the yields of the β anomers are generally comparable with earlier condensation methods that use psicofuranosyl- halide², 2-benzoates⁴ or 2-nitro derivative⁵. However, the present method has the advantage that the starting sugar 4 is more readily accessible. The precursor 6′-alcohol can be prepared in very large amounts from D-fructose using the method of Prisbe et al.⁴     

A Convenient Approach to the Synthesis of Azido-Acyclic Nucleosides

Abstract

The azidation of unprotected acyclic nucleosides (4) was carried out in a one-pot reaction by means of the reagent triphenylphosphine-carbon tetraiodide-sodium azide to give the corresponding mono-azido-acyclic nucleosides (6) in good yields without by-products such as the di-azido-acyclic nucleosides.     

Synthetic Studies on Guanofosfocin: Glycosylation of 8-Oxo-purine Nucleosides via Mitsunobu Reaction

Abstract

In model studies directed to the total synthesis of guanofosfocins, a unique glycosidic bond formation between the 8-oxo-purine nucleosides and mannopyranose derivatives under Mistunobu conditions is described.     

Electrochemical Oxidations of Some Purine Nucleosides. Formation of Some Novel Purine Oligonucleosides

Abstract

The electrochemical oxidation of the purine nucleosides xanthosine and guanosine at carbon electrodes has been studied. The initial electrochemical event is a 1e-, 1H+ oxidation to give free radicals which undergo a series of follow-up chemical and electrochemical reactions which lead to formation of a new class of purine oligonucleosides.     

Carboxyamidation of Purine Nucleosides: New Secondary 8-Carboxamidopurine Nucleosides

Abstract

Palladium catalyzed carboxyamidation at the 8-position of 8-bromoadenosine and 8-bromoguanosine nucleosides is a versatile reaction, which allows primary, secondary, heterocyclic, aromatic mine and amino acids to be incorporated into purine nucleosides.     

Synthesis of 1,5-Anhydro-D-Mannitol Nucleosides with a Purine Base Moeety

Abstract

D-Mannitol nucleosides with a purine base moiety have been conveniently synthesized strating from 1,5-anhydro-4,6-O-benzylidene-D-glucitol. The 3-OH function of 1,5-anhydro-4,6-O-benzylidene-D-glucitol was selectively protected with t-butyldimethylsilyl group and subsequently converted to the corresponding 0-triflate derivative for the introduction of the nucleobase moietes. These nucleoside derivatives were transformed to 1,5-Anhydro-6-O-MMTr-2-(N⁶-benzoyladenin-9-yl)-2-deoxy-3-O-TBDMS-D-mannitol and 1,5-Anhydro-6-O-MMTr-2-(N²-isobutyryl-guanin-9-yl)-2-deoxy-3-O-TBDMS-D-mannitol, useful as the building blocks for oligonucleotide synthesis. Also, the synthesis of the corresponding fully deprotected anhydrohexitol nucleosides were achieved for evaluation of antiviral activity test.     

Transglycosylation Reactions of Purine Nucleosides. A Review

Abstract

Mechanism, regio- and stereoselectivity, reversibility as well as some practical applications of transglycosylation reactions in the chemistry of purine nucleosides are reviewed. There are two main reaction pathways of glycosylation and transglycosylation in the purine series; i) the better known and generally accepted 3→9 sequence of adenine and its derivatives ii) the equally conceivable 7?9 mechanism for guanine and other 6-oxopurines, which is hereby supported by the author's study.

     

Synthesis and Bioactivity of Novel Trisubstituted Triazole Nucleosides

A series of novel trisubstituted 1,2,3-triazole purine nucleosides were efficiently synthesized via Huisgen 1,3-dipolar cycloaddition in good yields. Bioactivity against cytomegalovirus (CMV) and varicella-zoster virus (VZV) in human embryonic lung cell cultures was evaluated and all compounds show low antiviral activity.     

A Novel Route for the Synthesis of Fluorodeoxy Sugars and Nucleosides

Abstract

Ring-fluorination of α- and β-D-pentofuranosides containing free secondary hydroxyl groups by (diethylamino)sulfur trifluoride (DAST) was studied.     

Novel Acyclic Analogues of Purine Nucleosides: 2,3-Dihydroxy-1-Methoxypropyl and 3-Hydroxy-1-Methoxypropyl Derivatives

Abstract

Novel purine nucleoside analogues in which the N-9 ribosyl moiety is replaced by a 2,3-dihydroxy-1-methoxypropyl or 3-hydroxy-1-methoxypropyl substituent and their N-7 substituted isomers have been synthesized and tested for antiviral activity.     

A Review: Synthesis of Aryl C-Glycosides Via the Heck Coupling Reaction

In this article, we focus on the synthesis of aryl C-glycosides via Heck coupling. It is organized based on the type of structures used in the assembly of the C-glycosides (also called C-nucleosides) with the following subsections: pyrimidine C-nucleosides, purine C-nucleosides, and monocyclic, bicyclic, and tetracyclic C-nucleosides. The reagents and conditions used for conducting the Heck coupling reactions are discussed. The subsequent conversion of the Heck products to the corresponding target molecules and the application of the target molecules are also described.     

Screening of Catalytically Active Microorganisms for the Synthesis of 6-Modified Purine Nucleosides

Modified nucleosides can be prepared by microbial transglycosylation from cheaper nucleoside precursors using free or immobilised whole cells. An efficient screening method to find transglycosylation activity in␣microorganisms was developed for the synthesis of 6-modified purine nucleosides, such as 6-chloro-, 6-methoxy-, 6-iodo- and 6-mercaptopurine ribonucleoside. Out of 100 microorganisms screened, Bacillus stearothermophilus ATCC 12980 was the best for this purpose.     

Synthesis of Some Novel Acyclolumazine N-1 Nucleosides

Abstract

Reactjon of (2-acetoxyethoxy)methyl bromide with the silylated lumazine bases (1-6) in the presence of n-Bu₄NI leads to the formation of the nucleosides 8, 10, 12, 14, 16 and 18 respectively. Deacetylation with methanolic ammonia afforded the free nucleosides 9, 11, 13, 15, 17 and 19, respectively, in good yields. Structural proofs of the newly synthesized compounds are based on elemental analyses, UV and ¹H-NMR spactra. None of the acyclic nucleosides exhibited antiviral activity against HSV-1 in vitro.     

Synthesis and Anti-HIV Activity of Different Novel Nonclassical Nucleosides

Abstract

A series of different novel nonclassical nucleosides have been synthesised and evaluated for their inhibitory activity against human immunodeficiency virus (HIV) replication in MT-4 cells.     

The Synthesis of Novel 5-Trifluoroethoxy Pyrimidine Nucleosides

Abstract

The syntheses of 5-(2, 2, 2-trifluoroethoxy)uracil, 5-(2, 2, 2-trifluoroethoxy)arabinouridine and 5-(2, 2, 2-trifluoroethoxy) uridine are described.     

Synthesis and Antiviral Activities of Some Novel Carbocyclic Nucleosides

Abstract

cis-3-Aminomethylcyclopentylmethanol (4), prepared from norbornene (5) in four steps and 51 % overall yield, was used as a precursor in the synthesis of carbocylic nucleosides 13–18 containing guanine and 8-azaguanine bases. None of these compounds had appreciable activity against fourteen viruses in the concentration range tested. Compounds 13 and 16 showed cytotoxicity to all or part of the cell lines used.     

Synthesis of Novel Fluoro Carbocyclic Purine Nucleoside Analogues

Abstract

ABSTRACT: The synthesis of four isomerically pure fluoro-carbocyclic adenosine and guanosine analogues is described.     

The Synthesis of Derivatives of 2-Arylamino ara-Carbocyclic Purine Nucleosides as Potential Anti-Viral Agents

Abstract

A general synthetic method into 2-arylamino ara-carbocyclic purine nucleosides from 2,4,6-mchloropyrimidine is described.     

Synthesis of Novel Olefinic Carbocyclic Purine Nucleoside Analogues

Abstract

The synthesis of optically pure unsaturated carbocyclic nucleoside analogues is described. (3,4S)-Bis(t-butyldiphenyl silyloxymethyl)-1R and 1S cyclopent-2-en-1-ol were coupled with 6-chloropurine and 2-amino-6-chloropurine respectively, using a modified Mitsunobu reaction. The products were reacted further using standard procedures to give compounds 12, 14, 16 and 18.     

Synthesis and Antimicrobial Evaluation of Novel Pyrazolones and Pyrazolone Nucleosides

The synthesis of a novel series of 4-arylhydrazono-5-methyl-1,2-dihydropyrazol-3-ones 4a–h, and their N ²-alkyl and acyclo, glucopyranosyl, and ribofuranosyl derivatives is described. K₂CO₃ catalyzed alkylation of 4a–h with allyl bromide, propargyl bromide, 4-bromobutyl acetate, 2-acetoxyethoxymethyl bromide, and 2,3,4,6-tetra-O-acetyl-α-D-glucopyranosyl bromide proceeded selectively at the N ²-position of the pyrazolinone ring. Glycosylation of 4a with 1,2,3,5-tetra-O-acetyl-β-D-ribofuranose under Vorbruggen glycosylation conditions gave the corresponding N ²-4-arylhydrazonopyrazolone ribofuranoside 9a in good yield. Conventional deprotection of the acetyl protected nucleosides furnished the corresponding 4-arylhydrazonopyrazolone nucleosides in good yields. Selected numbers of the newly synthesized compounds were screened for antimicrobial activity. Compounds 4b, 12a, and 14d showed moderate activities against Aspergillus flavus, Penicillium sp., and Escherichia coli.