A Novel and Practical Synthesis of<scp>l</scp>-Hexoses from<scp>d</scp>-Glycono-1,5-lactones

Abstract

A novel and efficient conversion of d -glycono-1,5-lactones into the corresponding l -sugars is described. The important intermediate, δ-hydroxyalkoxamates, was provided by a practical alkoxyamination of d -glycono-1,5-lactones mediated by Me 3 Al. In contrast to the preparation of β-lactam skeletons from β-hydroxyalkoxamates, the cyclization of δ-hydroxyalkoxamates under Mitsunobu conditions resulted in O -alkylation rather than N -alkylation. It is noteworthy that δ-hydroxyalkoxamates derived from d -mannono-1,5-lactones afforded the O -alkylation product in 91% yield. None of the N -alkylation product was detected in this case. These O -cyclized oximes, in which the inversion of the configuration at C5 was secured, were efficiently converted into the l -sugars.