For the last four years, our research group has been concerned with the interaction of aldehydes and ketones with amino acids and simple peptides and their derivatives. Thus far, we have studied a fairly general reaction between carbonyl compounds (acetone, cyclohexanone, cyclopentanone, or isobutyraldchyde) and dipeptides' which has afforded novel imidazolidine ring systems. In general, polyhalogenated ketones react quite ...