Synthesis of chiral pyranocyclohexane, oxepanocyclohexane, and furylpyran and -oxepane systems by the application of intramolecular nitrone and nitrile oxide cycloaddition of carbohydrate derivatives

Abstract

Chiral nonracemic pyranocyclohexanes 7 and 8 and oxepanocyclohexane 11 and 12 were obtained from a single 1,2-isopropylidene-3- O-cyclohexenyl carbohydrate aldehyde 4 via intramolecular nitrile oxide cycloaddition, and were converted to 2-(2′-tetrahydrofuryl)pyran 28, which incorporates the lasalocid skeleton, and the related oxepane derivative 32 respectively, through modification of the furanoside ring by applying 2- O-allyl carbohydrate nitrone cycloaddition.