Preparation of arenesulfinic esters of 1,2:5,6-Di-O-cyclohexylidene-α-D-glucofuranose, and their conversion into optically active sulfoxides

Abstract

Arenesulfinyl chlorides react readily with 1,2:5,6-di-O-cyclohexylidene-α-D-glucofuranose in the presence of pyridine to afford the corresponding arenesulfinates. The ratio of diastereoisomeric sulfinates formed exceeds 2 : 1 with the major diastereoisomer possessing the (R)-configuration at sulfur. The diastereoisomeric esters are oils and were separable only in the case of the mesityl derivative when the crystalline, optically pure (R)-mesitylenesulfinic ester was isolated.

Treatment of the diastereoisomeric sulfinates with Grignard reagents gives optically active sulfoxides in enantiomeric excess corresponding to the diastereoisomeric excess in the esters. Careful recrystallization of these optically impure sulfoxides leads to optically enriched products in favourable cases.