synthesis of new 2',3'-dideoxy-C-nucleosides structurally related to didanosine has been achieved. Their preparation involved condensation of a suitably substituted, lithiated 2- or 4-picoline with 2',3'-dideoxy-5'-benzylribonolactone, followed by borohydride reduction of the resulting hemiacetals, intramolecular Mitsunobu cyclization of the derived diols, formation of the pyrazolo[3,4-c] or [4,3-b]pyridine