Synthesis of 4,6-diedoxy- d- and - l-hexoses from racemic and meso-dipropenylglycol

Abstract

Rac- and meso-divinylglycols offer, via site-selective epoxidation, a versatile strategy for the synthesis of optically pure sugars. This is exemplified in this paper by the synthesis of 4,6-dideoxyhexoses. Starting from mono- O-benzyl di-(1-propenyl)glycol, readily obtained from racemic-di-1-propenylglycol[(±)- 1] with the help of Sharpless epoxidation, the 3 d and 3 l diol-epoxides, respectively, were synthesized in enantiomeric pure form. Regioselective reductive cleavage of the epoxide ring and ozonolysis of the CC-double bond gave 2- O-4,6-dideoxy- d- and - l- xylo-hexose ( 5 d and 5 l) respectively, in only four steps from racemate[(±)- 1]. The transformation of compound 5 l into l-chalcose is described. Similarly, mono- O-benzylation of meso-dipropenylglycol and subsequent Sharpless epoxidation in the presence of diethyl (+)-tartrate gave selectively an l-diolepoxide, which was transformed readily into 4,6-dideoxy- l- lyxo-hexose and 4,6-dideoxy-3- O-methyl- l- lyxo-hexose.