Deprotonation of N‐protected alanine esters with LDA, and subsequent addition of various metal salts, most likely results in the formation of chelated metal enolates. Aldol reactions of these enolates with aldehydes afford the anti isomers of α‐methyl α‐amino‐β‐hydroxy acid derivatives in a highly diastereoselectiv fashion. Best results are obtained with tin enolates of N‐sulfonylated alanine esters, which give excellent results with both aliphatic and aromatic aldehydes. Employing the SES‐protected derivatives which show the same good yield and diastereoselectivity as the corresponding Ts‐protected esters, allows the preparation of the free α‐methylserines.

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