Stereospecific synthesis of nucleosides by the fusion reaction

Abstract

A study of the fusion of 1-O-acetyl-2,3,5-tri-O-benzoyl-D-arabinofuranose [α/β(4:1)] with 2,6-dichloro-purine or 7-methylthio-ν-triazolo[4,5-d]pyrimidine to produce 9-(2,3,5-tri-O-benzoyl-α-D-arabinofuranosyl)-2,6-dichloropurine and 1-, 2-, and 3-(2,3,5-tri-O-benzoyl-α-D-arabinofuranosyl)-7-methylthio-ν-triazolo[4,5-d]pyrimidines, respectively, revealed that the β-anomer of the starting sugar was unreactive in the fusion reaction (without acid catalyst), presumably owing to the inability of the 2-O-benzoyl group effectively to provide anchimeric assistance in the presence of a cis-OAc group at the reaction site.