Antihistaminic and other biological activities of 2-methylpropanamide and benzamide derivatives of carboxyterfenadine

In the present study the 2-methylpropanamide and benzamide derivatives of carboxyterfenadine, have been synthesized by nucleophilic substitution at carboxylic acid moiety (C-33) of tertiary carbon C-19 substituted with benzene ring. The proficient and high yielding series was carried out in two steps by continuous monitoring with TLC. The carboxylic group was utilized in the formation of 2-methylpropanamide and benzamide derivatives of carboxyterfenadine. The derivatives were characterized by spectroscopic techniques including mass. The starting material (2-[4-[1-hydroxy-4-[4-(hydroxydiphenylmethyl)piperidino]butyl]phenyl]-2-methylpropanoic acid) itself is H1 receptor antagonist. Hence, all these compounds A-E were biologically evaluated for antihistaminic and anticholinergic activity, using isolated guinea pig ileum tissues.