Abstract PX-α-cyano-β-styrenyl esters (X= H, Cl, CF 3, NO 2) of N-benzyloxycarbonyl valine were prepared. The rate constant for amide formation with methyl valinate was assayed; it increases with increasing electron attracting power of the para substituent. The N- hydroxysuccinimidoyl ester and the pH-α-cyano-β-styrenyl ester of valine have comparable reactivities.
