Consecutive elongation of alanine oligopeptides at the second time range under hydrothermal conditions using a microflow reactor system.

During the course of the study of the hydrothermal stability of alanine oligopeptides, a small amount of oligopeptides longer than the starting oligopeptides was found in the reaction products. On the basis of this unexpected finding and the investigation of the reaction mechanism, the elongation of oligopeptides using (Ala)3, (Ala)4, and (Ala)5 was attempted in aqueous solution at 275-310 degrees C within the second time range using a microflow reactor system. The elongation of (Ala)4 and (Ala)5 succeeded in the presence of an excess amount of Ala monomer. This is probably due to the fact that the elongation rate is competitive or somewhat faster than the degradation of peptide bonding. On the contrary, the elongation of (Ala)3 was not possible since it was immediately converted to diketopiperazine.