Diastereoselective cycloaddition of bromonitrile oxide to sugar derived chiral alkenes. A possible route for the synthesis of higher deoxysugars

Abstract

Bromonitrile oxide formed in situ from dibromoformaldoxime reacts with the sugar derived alkenes 1, 2, 3, 4, to give bromoisoxazolines in satisfactory yields. All the reactions show high regio-and stereoselectivity. Reactions with the ω-unsaturated alkenes 1 and 2 are regiospecific and diastereoselective affording a pair of diastereomers. The reaction with furanone 4 is regioselective and stereospecific affording one pair of regioisomers, whereas the reaction with the glycal 3 is both regiospecific and stereospecific and gives only one isomer. The possible utility of the obtained isoxazolines as useful synthetic intermediates is further proved by transformation of isoxazoline 7 to 7-deoxy octose derivative 16.