Abstract 1-Substituted 5, 6-dihydrouracils (VI) and 1-substituted 5, 6-dihydrocytosines (V) were prepared by cyclization of N-substituted N-β-cyanoethyl ureas (IV) in acid and basic medium, respectively. Compounds N were synthesized from cyanic acid and β-(substituted amino) propionitriles (III), the latter in turn were prepared from primary amines (I) and acrylonitrile (II).
