Synthesis and antitumor activity of N-terminal proline-containing peptide-(chloroethyl)nitrosoureas

The N alpha-(2-chloroethyl)-N-nitrosocarbamoyl derivatives of H-Pro-Lys(X)-Pro-Val-NH2 (X: tert-butyloxycarbonyl, formyl, (2-chloroethyl)nitrosocarbamoyl) were synthesized. It was found that the bis-substitution of the urea N3 in these derivatives does not decrease the antitumor activity influenced mainly by the nature of the carrier molecule as a whole.