Alkylation of Amino Acids without Loss of Optical Activity: α‐ and β‐Alkylation of an Aspartic Acid Derivative

The α-alkylation of β-heterosubstituted carbonyl compounds leads to a surprising result in the case of L-(+)-N-formylaspartic acid di-tert-butyl ester: A mixture of the β- and α-substituted aspartic acid derivatives (1) and (2) (ca. 7:2) is obtained. The erythro-isomers of (1) are formed stereospecifically, while, interestingly, an enantiomer of (2) is formed in excess; RCH3, C2H5, CH2CHCH2, CH2C6H5.