61638-07-1

A series of phenethylamine derivatives with various ring substituents and with or without N-methyl and/or C-α methyl or ethyl groups was synthesized and assayed for their ability reversibly to inhibit monoamine oxidase A (MAO-A) and monoamine oxidase B (MAO-B). Several compounds showed potent and selective MAO-A inhibitory activity (IC50 in the submicromolar range) but none showed appreciable activity toward MAO-B. A three-dimensional quantitative structure-activity relationship study for MAO-A inhibition was performed on the series using comparative molecular field analysis (CoMFA). The resulting model gave a cross-validated q2 of 0.72 and showed that in this series of compounds steric properties of the substituents were more important than electrostatic effects. Molecular modeling based on the recently published crystal structure of inhibitor-bound MAO-A provided detailed evidence for specific interactions of the ligands with the enzyme, supported by previous references and consistent with results from the CoMFA. On the basis of these results, structural determinants for selectivity of substituted amphetamines for MAO-A are discussed.

The syntheses and physical properties are described for 2,5 dimethoxy 4 methylthiophenylethylamine and 2,5 dimethoxy 4 methylthiophenylisopropylamine. The latter compound is the sulfur analog of the psychotomimetic phenylisopropylamines 2,4,5 trimethoxyphenylisopropylamine and 2,5 dimethoxy 4 methylphenylisopropylamine wherein the methylthio group replaces a methoxy group or a methyl group, respectively. This compound is predicted to be about 30 times as active as mescaline.