to investigate the structural determinants for chymotrypsin suicide inactivation with haloenol lactones , we prepared a series of nine lactones , differing in ring size ( 6-membered valerolactones and 5-membered butyrolactones ) and in the nature of the aromatic substituent ( phenyl and alpha-naphthyl ) , and the halogen ( bromine and iodine ) .
C0018544
halogen
C0006223
bromine