Optically active catecholimidazolines: a study of steric interactions at .alpha.-adrenoreceptors

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Abstract
The optical isomers and deoxy form of 2-(3,4,.alpha.-trihydroxybenzyl)imidazoline hydrochloride (1) were examined for their .alpha.-adrenergic activity on rat aorta. The rank order of stimulant activity was deoxy (2) .simeq. (R)-(-)-1 > (S)-(+)-1. For catecholamines, the order of activity is (R)-(-)-epinephrine > (S)-(+)-epinephrine = epinine (deoxyepinephrine). The relative order of potency for the isomers of 2-(3,4,.alpha.-trihydroxybenzyl)imidazoline is different than that predicted by the Easson-Stedman theory for stereoisomers of catecholamines. Substitution of the deoxy compound 2 with substituents, methyl or benzyl, in the 4-position lowers the .alpha.-adrenergic agonist activity, and differences observed between optimal isomers were small.