Amides of carbobenzoxyglycine, carbobenzoxyalanine, and carbobensoxyphenylalanine have been found to react with carbonyl compounds (isobutyraldehyde, benzaldehyde, and cyclohexanone), in the presence of a sulfonic acid catalyst, to give two types of products: 1- carbobenzoxy-4imidazolidinones (111) and carbobenzoxyamino acid 1-isobutenylamides (IV). The structure of the products is predetermined by the structure of the amide and that ...