Peptides Containing Aminophosphonic Acids. II. The Synthesis of Tripeptide Analogs

Abstract The synthesis of tripeptides containing aminophosphonic acid was attempted as follows. Diethyl phthalylimidomethyl phosphonate (I) was chlorinated with phosphorus pentachloride to the phosphonomonochloridate (II), which was then coupled with amino acid ethyl esters to give the corresponding dipeptides (IIIa—c). The phthalyl groups of III were removed with hydrazine, and the resulting free amines were subsequently combined with phthalyl-amino acids by means of dicyclohexylcarbodiimide to produce the tripeptide analogs (IVa—c) in good yields.