Synthesis of septanosides through an oxyglycal route.

A new route to synthesize septanoside derivatives from protected 2-hydroxyglycals is reported. Ring expansion of a pyranoside to a septanoside was achieved through key reactions of a cyclopropanation, ring opening, oxidation, and reduction. Methyl septanoside derivatives, namely, methyl alpha-D-glycero-D-talo-septanoside and methyl alpha-D-glycero-l-altro-septanoside, were synthesized in an overall yield of 35% and 46%, respectively, from the corresponding protected 2-hydroxy glycals.