Condensation Reaction Between α-Amino Acid Phenylhydrazides and Carbonyl Compounds

The natural α-amino acid phenylhydrazides 1a-d readily react with the aldehydes 2a-d and ketones 2e-h to produce the 3-(phenylamino)imidazolidin-4-one derivatives 4 in good yields. Their structures were confirmed by X-ray structural analysis. Polycyclic systems were obtained from the reaction of L-tryptophan phenylhydrazide (1d) and L-histidine phenylhydrazide (1e) with benzaldehyde (2c), which gave 1,10-diphenyl-2-(phenylamino)-2,9,10a-triazacyclopenta[b]fluoren-3-one (5dc) and 4,6-diphenyl-7-(phenylamino)-3,4,6,7,8a,9-hexahydro-8H-diimidazo [1,5-a:4′,5′-d]pyridin-8-one (5ec), respectively.