Hydroxyindole-O-methyltransferase. 3. Influ- ence of the phenyl moiety on the inhibitory activities of some N-acyltryptamines.

During previous studies on the inhibition of hydroxyindole-O-methyltransferase, several N-acyltryptamines have been found to be good inhibitors of this enzyme. Substitution of the benzyl or phenyl moiety of N-phenylacetyltryptamine or N-benzoyltryptamine with halogen atoms further enhanced the inhibitory activity. Among all the halogen-substituted inhibitors, the 3,4-dichloro substitution offered the highest activity. An increase in inhibition of the enzyme was also observed when a fluorine or bromine atom was placed on C-5 position of the indole nucleus. A combination of the 5-bromo and 3,4-dichlorobenzoyl substitutions resulted in the most active inhibitor.