2-DEOXY-3-C-(HYDROXYMETHYL)-D-PENTOFURANOSE DERIVATIVES - STEREOSELECTIVE SYNTHESIS AND CONVERSION INTO A NOVEL CLASS OF NUCLEOSIDE ANALOGS

Oxidation of pure anomers of 5-O-monoprotected methyl 2-deoxy-D-ribofu ranosides 3-6 followed by Lombardo methylenation afforded the novel 3- C-methylene pentofuranosides 11-14. Subsequent osmium tetraoxide-catal yzed dihydroxylations of 11, 13, and 14 afforded a mixture of erythro- and three-configured S-C-hydroxymethyl furanosides 15/16, 18/19, and 20/21, respectively. However, analogous dihydroxylation of 5-O-(4-phen ylbenzoyl)-protected beta-anomer 12 proceeded with complete stereosele ctivity to give 3-C-(hydroxymethyl)-beta-D-erythro pentofuranoside 17 in 76% yield. Conversion of 17 to the corresponding primary tosylate 2 2, followed by base-catalyzed nucleophilic attack by the nucleobases a denine and thymine, afforded after deprotection compounds 25 and 26, r espectively, as the first examples of a novel class of nucleoside anal ogues.