Highly enantioselectlve phase-transfer-catalytic alkylation of 2-phenyl-2-oxazoline-4-carboxylic acid tert-butyl ester for the asymmetric synthesis of α-alkyl serines

Abstract

A facile synthesis of chiral α-alkyl serines 3 involves the asymmetric alkylation of substrates 1 with alkyl halides (RX) under phase-transfer catalysis (PTC), followed by acidic hydrolysis of the alkylation products 2. The phenyl oxazoline moiety enhances the acidity of the α proton of the ester and is an excellent protecting group for both the amino and hydroxy functions of the serine ester.