Abstract With the assistance of inorganic phosphorus, a-amino acids could self-assemble into a series of oligopeptides, so it could provide a new route to synthesize peptides. In this paper, the self-assembly reaction of L-trytophan mediated by phosphorus oxychloride was monitored by using ESI-MS. The proper condition of the self-assembly reaction of L-Try was reported. The reaction products were purified by RP-HPLC and the fragmentation pathway ...