Antineoplastic agents. 2. Structure-activity studies on N-protected vinyl, 1,2-dibromoethyl, and cyanomethyl esters of several amino acids.

Previously reported work on N-protected activated esters of phenylalanine has been extended to include N-protected vinyl, dibromoethyl, and cyanomethyl esters of several other amino acids. These compounds have been synthesized and evaluated in Ehrlich ascites carcinoma, Walker 256 carcinosarcoma, and and P388 lymphocytic leukemia tests. Among compounds tested were derivatives of tyrosine, tryptophan, glycine, leucine, proline, aspartic acid, glutamic acid, 4-aminobutyric acid, and 6-aminocaproic acid. Compounds of greatest potential interest from this study are N-carbobenzoxyglycine 1,2-dibromoethyl ester and N-carbobenzoxy-L-leucine 1,2-dibromoethyl ester. Both compounds were highly active in Ehrlich ascites test systems (33 mg/kg/day). The glycine derivative was also active in the Walker 256 test (2.5 mg/kg/day. Values for LD50's in mice were 148 mg/kg (0.37 mmol/kg) and 225 mg/kg (0.50 mmol/kg) for glycine and leucine derivatives, respectively; therefore, these compounds do not appear to be toxic at effective dose levels.