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; RCH 3 , C 2 H 5 , CH 2 CHCH 2 , CH 2 C 6 H 5 .