Bicyclic nucleoside analogues, 3'-O,4'-C-methyleneribonucleosides 1, includ
ing thymine, cytosine, adenine and guanine nucleobases, were conveniently s
ynthesized from D-glucose, and the ribofuranose ring of 1 was found to exis
t predominantly in a S-conformation by means of H-1 NMR and X-ray analysis.