The title anions, when a-alkyl substituted, alkylate selectively in the y-position with hindered a-bromoesters. A lower degree of hindrance in either or both reactants tends to favour a-alkylation. The alkylation of the anion of Schiff bases derived from a-aminoesters has been widely exploited' since its development by the Stork group2 as a convenient route to various asubstituted a-aminoacids. In all reported cases the alkylation of the ambident anion (1) appears to be regiospecific, giving only the a-alkylated product. During the synthesis of novel a,a-disubstituted a-aminoacids, we reacted the lithium salt (2) of N-benzylidenealanine benzyl ester with i-butyl 2-bromo-3-phenylpropionate (3) under the usual conditions2 C-78', HMPTA-THF, LiN(_iPr)2] and hydrolysed the crude product with 1M aqueous citric acid to selectively remove the benzylidene function. Chromatography of the citric acid-soluble basic products gave, to our surprise, none of the desired aalkylated product (4). Instead, two new amine diastereoisomers were isolated in 221jm.p. 38-g') and 14% (m.p. 94-5') yield. In each case, 'H n.m.r. indicated the absence of the benzyl ester function and the a-methyl group derived from the anion and the presence of two phenyl rings, corresponding to the structure (5).' These isomers must result from v-alkylation in a selective process which is, to the best of our knowledge, unprecedented in this system. From the neutral hydrolysis products, benzyl pyruvate was isolated in 30% yield,a