Unexpected formation of oxetanes during the synthesis of dodeco-6,7-diuloses

Abstract

During the synthesis of symmetrical dodeco-6,7-diuloses that are potential candidates for inhibition of glycosidases, an unanticipated epoxide-oxetane rearrangement was observed. A bicyclic sugar consisting of a glycal moiety and an anomeric esterified furanose was oxidized under epoxidation conditions (mCPBA/KF). The isolation of the pure epoxide was not possible since a rapid reversible conversion accompanied by the migration of the ester group took place and resulted in the formation of an unusual oxetane-bridged disaccharide scaffold. X-ray diffractometric structure elucidation and the suggested mechanism of the rearrangement are provided.