Analogs of the cytostatic cyclic tetrapeptide chlamydocin. Synthesis of N.beta.-(N-maleoylglycyl) and N.beta.-(tert-butyloxycarbonyl) derivatives of cyclo(Gly-L-Phe-D-Pro-L-Dap)

Abstract
The synthesis of analogs of the cytostatic [antitumor] cyclic tetrapeptide chlamydocin is described. The maleoyl cyclic tetrapeptide did not inhibit [3H]thymidine incorporation into calf thymus lymphocytes at concentrations 1000-fold higher than the IC50 for chlamydocin (6 nM).