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Several dihydro and carbocyclic analogues of tryptamine were evaluated in order to determine the role of the heterocyclic portion of the indole nucleus on the interaction of indolealkylamines with the serotonin receptors of the rat fundus. Reduction of the C2--C3 double bond or replacement of the indole nitrogen with an sp3-hybridized carbon atom results in a 50% decrease in receptor affinity. Complete removal of the five-membered ring of N,N-dimethyltryptamine reduces affinity by an order of magnitude. It appears that an intact indole nucleus, though not entirely necessary, results in an optimal receptor interaction for the indolealkylamines examined.

Several alkylpiperazines, monocyclic subfragments of known tricyclic neuroleptic agents, were evaluated as dopamine antagonists in the isolated rabbit ear artery preparation. Compound prepared and evaluated are of the general structure Ar-X-(CH2)n-Y, where X = C, O, and N, n = 1-3, and Y, for the most part, was 4-methylpiperazine. Those compounds where X - NH, n = 3, and X = (Z)-CH - CH, n = 2, with an electron-withdrawing group meta to the side chain, possess dopamine antagonist activity comparable to that of clozapine. It is concluded that the entire tricyclic structure of phenothiazine-like agents (or at least more than a monocyclic ring system) is necessary for optimal activity as a dopamine antagonist in the receptor preparation used in this study.

This communication outlines the development of a novel, general synthetic route to substituted α‐tetralones 5, their subsequent conversion to the α,β‐unsaturated ketones 11, and an improved, one‐step transformation of 11 to the tricyclic title compounds 1. Thus, substituted derivatives of 1 can be prepared in six steps from simple benzaldehydes, or, in three steps from more readily available α‐tetralones.