Reaction of aminoquinolines with maleic acid and its diethyl ester gave N-quinolylaspartic acids or their esters. In aqueous media 4-aminoquinoline formed a maleate or betaine. Hydrazides of aspartic acids were prepared, and N-(3- and 6-quinolyl)aspartic acids were converted into 5-carboxymethyl-1- quinolylimidazolidin-4-one-2-thiones.