The synthesis of new 4-(trifluoromethy1) benzoic acid derivatives 2-10 and their coupling with amino acids and peptides 12, 13, 15 is described. They serve as precursors for the synthesis of the hitherto unknown demethyl (trifluoromethy1) actinocin dimethyl esters 11, demethyl-trifluoromethyl-actinocinyl peptides 14, 16, 18 and the demethyl-trifluoromethyl- actinomycins 17. Although spacially comparable with the methyl residues, the 4-and 6- ...