Diastereoselectivity in Epoxidation of Carbohydrate Fused [13]-Macro-dilactones

DMDO epoxidation of carbohydrate fused [13]-macro-dilactones was found to be highly diastereoselective. Facial selectivity of the epoxidation depended on the identity of the fused carbohydrate. Gluco-configured macro-dilactones gave the R,R epoxide, whereas the galacto- configuration gave the S,S epoxide. The epoxide stereochemisty was confirmed by independent syntheses of dimethyl 4R,5R-epoxyoctanedioate via Shi epoxidation of dimethyl E-oct-4-enedioate and by transesterification of the epoxide derived from the gluco-[13]-macro-dilactone. We demonstrate diastereoselectivity in alkene reactivity driven by remote rather than adjacent stereocenters.