Synthesis, biological evaluation, and quantitative structure-activity relationship analysis of [.beta.-(aroylamino)ethyl]piperazines and -piperidines and [2-[(arylamino)carbonyl]ethyl]piperazines, -piperidines, -pyrazinopyridoindoles, and -pyrazinoisoquinolines. A new class of potent H1 antagonists

Some [beta-(Aroylamino)ethyl]piperazines and -piperidines and [2-[(Arylamino)carbonyl]ethyl]piperazines, -piperidines, -pyrazinopyridoindoles, and -pyrazinoisoquinolines have been synthesized and their H1-antagonistic activity studied in isolated guinea pig ileum. Quantitative structure-activity relationship analysis indicates that the hydrophobicity of the side chain of these compounds plays a major role in their activity while steric and electronic factors are of secondary importance. All these compounds act on a common receptor and appear to interact similarly with the receptor.