Conjugates of 3‐hydroxy‐ 3‐methoxy‐ and the 3‐phenoxybenzoic acids, (the major metabolites of many pyrethroid pesticides) with acetyl‐ and benzoylornithine were synthesized by means of succinimidyl ester method orN‐ethyl‐N'‐(3‐dimethylaminopropyl)carbodiimide mediated couplings. Methyl esters were removed by alkaline hydrolysis. Hydrogenolysis of N2‐substituted N5‐benzyloxy‐carbonylornithine methyl ester derivatives gave corresponding 3‐acylaminopiperidones. The glycylvaline methyl esters were prepared by stepwise lengthening starting with valine methyl ester usingN‐ethyl‐N‘‐(3‐dimethylaminopropyl)carbodiimide as coupling reagent to introduce N‐t‐butyloxycarbonylglycine followed by coupling with the appropriate acid after the N‐t‐butyloxycarbonyl group removal.