Synthesis of Oxepines and 2-Branched Pyranosides from a <scp>d</scp>-Glucal-Derived <i>gem</i>-Dibromo-1,2-cyclopropanated Sugar

Abstract

The conversion of cyclopropane-fused carbohydrates into oxepines is an attractive method for accessing diverse members of the septanoside family of carbohydrate mimetics. 2-Bromooxepines are obtained through silver(I)-promoted thermal ring expansion of a d-glucal-derived gem-dihalocyclopropanated sugar. In contrast, cyclopropane ring cleavage under basic conditions leads to 2-C-branched pyranosides, not the 2-bromooxepine structures assigned in an earlier report.