Asymmetric aza-[2,3]-Wittig sigmatropic rearrangements: Chiral auxiliary control and formal asymmetric synthesis of (2S, 3R, 4R)-4-hydroxy-3- methylproline and (-)-kainic acid

Article abstract of DOI:10.1039/b506198a

A survey of 16 different chiral auxiliaries and a variety of strategies found that an (-)-8-phenylmenthol ester of a glycine derived migrating group can control the absolute stereochemistry of aza-[2,3]-Wittig sigmatropic rearrangements with diastereoselectivities of ca. 3 : 1 with respect to the auxiliary. In two specific examples, ca. 50% yields of enantiomerically pure products were obtained after chromatographic purification. These were synthetically manipulated with no erosion of stereochemistry into intermediates that completed formal asymmetric syntheses of (+)-HyMePro and (-)-kainic acid. The Royal Society of Chemisrry 2005.