Synthesis of analogues of the melanocyte-stimulating hormone release-inhibiting factor containing 2-oxoimidazolidine-1-carboxylic acid

2-Oxoimidazolidine-1-carbonyl-leucyl-glycine amide (I), 2-oxoimidazolidine-1-carbonyl-leucyl-β-alanine amide (II), and 2-oxoimidazolidine-1-carbonyl-leucine amide (III) were synthesized by the acylation of corresponding dipeptide or amino-acid esters with 2-oxoamidazolidine-1-carbonyl chloride and following ammonolysis. Analogues I and II, containing 2-oxoimidazolidine-1-carboxylic acid instead of proline, exhibited the antiamnestic activity in the doses of 1 mg per kg subcutaneously, III was without effect.