N-PENTENYL GLYCOSIDES AS MEDIATORS IN THE ASYMMETRIC-SYNTHESIS OF MONOSUBSTITUTED CHIRAL NONRACEMIC TETRAHYDROFURANS AND GAMMA-LACTONES

N-Pentenyl glycosides can be oxidatively hy-drolyzed by treatment with N-bromosuccinimide, previous work having been focused on the usefulness of the resulting glycosyl moiety. In this paper, attention is focused on asymmetric induction in the 2-(bromomethyl)furan that is liberated. The enantiomeric excess depends strongly on the orientations at the anomeric centers and at C2, as well as on the protecting group on the C2 oxygen. a-Anomers display higher asymmetric induction, and rationalization of this observation is based on the assumption that the molecule reacts from the favored ground-state orientation, wherein the exo anomeric effect is displayed. The usefulness of this route to optically active furans has been probed by a synthesis of an insect pheromone from the Bledius species. © 1990, American Chemical Society. All rights reserved.