Stereospecific C=β-Glycosidation and Synthesis of 4,7-Anhydro-5,6-isopropylidene-4 (S), 5(S), 6(R), 7(R)-Tetrahydroxyoxocan-2-one

Abstract

Wittig reaction of 2,3-O-isopropylidene-5-O-panisyldiphenylmethyl-β-D-ribofuranose (2) with methoxycarbonyl-methylene triphenylphosphorane was accompanied by spontaneous cyclization to generate 3 stereospecifically. Deprotection of 5-OH followed by mild base hydrolysis and cyclization with Py-Ac₂O-DBU then yielded 4,7-anhydro-5,6-isopropylidene-4(S), 5(S), 6(R), 7(R)-tetrahydroxyoxocan-2-one (5) in good overall yield.