Regioselective and stereoselective glycidic oxirane ring opening: a new entry to optically pure #alpa#-alkyl #alpha#-hydroxy #beta#-amino acid derivatives

摘要

The BF_3.OEt_2 catalyzed oxirane ring opening of glycidic estrs or amides with acetonitrile afforded the corresponding 2-oxazolines under very mild conditions in good yields. The reactions are completely regioselective (the nitrogen attacks the #beta#-carbon) and stereoselective (with inversion of configuration) starting from 2-alkyl or 2,3-dialkyl glycidic derivatives, but the stereoselectivity is lost and the regioselectivity is completely inverted from 2-aryl derivatives. The 2-oxazolines obtained are readily hydrolyzed into #beta#-amino, #alpha#-hydroxy esters or amides.