Glycosylation of nucleoside bases with 2,3-dideoxy-1-thio-D-glycero-pento-2-enofuranosides.

Both intermolecular and intramolecular glycosylation of thymine using phenyl 2,3-dideoxy-1-thio-D-glycero-pent-2-enofuranoside as a glycosyl donor was investigated. When the reaction was carried out intermolecularly in the presence of NBS as the promoter, the corresponding 2',3'-unsaturated beta-nucleosides were obtained stereoselectively. On the other hand, the intramolecular glycosylation employing a 5-O-(2-pyrimidyl) derivative of similar thioglycoside afforded an unexpected product, in which thymine was incorporated at the C-3' position.