The Schiff base derived from glycine ethyl ester and p-chlorobenzaldehyde can be alkylated by the ion-pair extraction method as well as under catalytic liquidliquid or solid-liquid phase-transfer conditions. This imine is compared with the corresponding benzophenone Schiff base.
Alkylation of glycine synthons represents an attractive
route for the synthesis of structurally diversified amino acids , especially when both L-and D-isomers are needed. Recently several examples of the direct alkylation of activated glycine esters have been described. 2 Initial studies have shown that the Schiff base 1 derived from benzaldehyde and glycine ethyl ester can be alkylated in the presence of strong bases under anhydrous condtions. 2a A more practical method involves the alkylation of the very stable Schiff base &prepared from benzophenone imine and glycine ethyl ester,under phase-transfer conditions.3 Although this ketimine is readily available,4 for practical considerations especially on a large scale, it would be even more convenient to alkylate aldimines derived from glycine esters. However, this could have presented difficulties due to the lower stability and acidity' of these Schiff bases.