Structure dependence in the solvolysis kinetics of amino acid esters

To better understand acyl transfer reactions of oligopeptides, seventeen N-acyl amino acid esters were solvolyzed in mildly basic methanol-d4. All show pseudo-first-order kinetics by 1H NMR. The rate constant varies up to 400-fold with the identity of the amino acid and up to 6200-fold with the identity of the N-acyl group. The impact of the N-acyl group on the rate constant is discussed in terms of crowding, amide conformation, and amide CO bond character.