New synthesis of 3′--substituted nucleosides

Glucose-derived 3'-(carboxymethyl)-3'-deoxyribonucleosides and 2', 3'-lactones as synthetic precursors for amide-linked oligonucleotide analogues

Treatment of a 1,2-O-isopropylidene-3-ketopentofuranose derivative (obtained from D-glucose) with [(ethoxycarbonyl)methylene]triphenylphosphorane and catalytic hydrogenation of the resulting alkene gave stereodefined access to 3-(carboxymethyl)-3-deoxy-D-ribofuranose derivatives. Esters of 5-O-acetyl- or 5-azido-5-deoxy-3-(carboxymethyl)-D-ribofuranose were coupled with nucleobases to give branched-chain nucleoside derivatives. Ester saponification and protecting group manipulation provided 2'-O-(tert-butyldimethylsilyl) ethers of 5'-azido-5'-deoxy- or 5'-O-(dimethoxytrityl) derivatives of 3'-(carboxymethyl)-3'-deoxyribonucleosides that are effective precursors for synthesis of amide-linked oligoribonucleosides.

Synthesis and antiviral activity of 3'-C-branched-3'-deoxy analogues of adenosine

The synthesis of some 3'-C-branched-3'-deoxy adenine nucleosides is described. Starting from the known 3-deoxy-3-C-(hydroxymethyl)-1,2;5,6-di-O-isopropylidene-alpha-D-allof uranose (1), a versatile glycosylating agent, namely 1,2-di-O-acetyl-5-O-benzoyl-3-deoxy-3-C-(mesyloxymethyl)-beta-D-ri bofuranose (6), was prepared in three steps. Condensation of the latter with bis(trimethysilylated) N6-benzoyladenine in the presence of tin(IV) chloride gave the N9-beta-nucleoside 7. Compound 7 was converted into (i) 9-[3-C-(azidomethyl)-3-deoxy-beta-D-ribofuranosyl]adenine (10), (ii) 9-[3-C-(azidomethyl)-2,3-dideoxy-beta-D-glycero-pent-2-enofuran osyl]adenine (14) and 9-[2-azido-3-C-(azidomethyl)-2,3-dideoxy-beta-D-arabinofuranosyl]a denine (15), and (iii) 9-[3-deoxy-2-O,3-C-(methylene)-beta-D-ribofuranosyl]adenine (16). None of the tested nucleosides showed marked cytostatic or antiviral activity in vitro.

Stereoselective synthesis, chemistry and antiviral evaluation of 1-(2,3-dideoxy-3-C-hydroxymethyl-beta-D-threo-pentofuranosyl)thymine derivatives

A series of novel 3'-C-branched 2',3'-dideoxynucleosides have been synthesized and evaluated as anti-HIV agents. Hydroboration of 2',3'-dideoxy-3'-C-methylene nucleoside proceeded regio- and stereoselectively to give 1-(2,3-dideoxy-3-C-hydroxy methyl-5-O-trityl-beta-D-threo-pentofuranosyl)thymine (5) after oxidation. 3'-C-Chloromethyl and 3'-C-iodomethyl 5'-O-protected 2',3'-dideoxynucleosides 9 and 12 were obtained from 5 by reaction with carbon tetrachloride/triphenylphosphine and methyltriphenoxyphosphonium iodide, respectively. Arbuzov reaction of 12 with triethyl phosphite afforded 3'-C-(diethyl-phosphono)methyl 5'-O-protected 2',3'-dideoxynucleoside 14. Compounds 5, 9, 12 and 14 were detritylated to give 1-(3-C-chloromethyl-2,3-dideoxy-beta-D-threo-pentofuranosyl)thymine (10), 1-(2,3-dideoxy-3-C-hydroxymethyl-beta-D-threo-pentofuranosyl)-thymine (11), 1-(2,3-dideoxy-3-C-iodomethyl-beta-D-threo-pentofuranosyl)thymine (13) and 1-(2,3-dideoxy-3-C-(O,O'-diethylphosphono)methyl-beta-D-threo- pentofuranosyl)thymine (15), respectively. These nucleoside analogues were evaluated for antiviral activity against human immunodeficiency virus type 1 (HIV-1) and herpes simplex virus type 1 (HSV-1) in vitro. Compound 5 demonstrated selective antiviral activity against HIV-1 but not HSV-1.