Synthesis of Quaternary α-Methyl α-Amino Acids by Asymmetric Alkylation of Pseudoephenamine Alaninamide Pivaldimine

The utility of pseudoephenamine as a chiral auxiliary for the alkylative construction of quaternary alpha-methyl alpha-amino acids Is demonstrated. The method is notable for the high diastereoselectivities of the alkylation reactions, for its versatility with respect to electrophilic substrate partners, and for its mild hydrolysis conditions, which provide alpha-amino acids without salt contaminants. Alternatively, alpha-amino esters can be obtained by direct alcoholysis.