ASYMMETRIC DIELS-ALDER REACTIONS EMPLOYING MODIFIED CAMPHOR-DERIVED OXAZOLIDIN-2-ONE CHIRAL AUXILIARIES

Transposition of the dormant methyl group from C-1 in chiral oxazolidi n-2-one 2 to C-7 in a six step synthetic sequence from (1R)-camphor 5 creates a novel transfigomer 4 with sufficient pi-topological bias to induce excellent levels of asymmetric induction in Lewis-acid catalyse d Diels-Alder reactions of its alpha,beta-unsaturated carboximide deri vatives with cyclopentadiene. Further modification of 4 by replacement of the C-7 methyl group with an ethyl substituent raises the level of diastereoselectivity for the acrylate derivative 11a from 81 to >95% d.e..