Syntheses and in vitro evaluation of 4-(2-aminoethyl)-2(3H)-indolones and related compounds as peripheral prejunctional dopamine receptor agonists

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Abstract
A series of (.beta.-aminoethyl)indolones and related compounds was synthesized and evaluated in vitro as peripheral prejunctional dopaminergic agonists in the field-stimulated isolated perfused rabbit ear artery. 4-[2-(Di-n-propylamino)ethyl]-7-hydroxy-2(3H)-indolone (26) was the most potent compound (ED50 = 2 .+-. 0.3 nM) tested, while the related secondary amine 24 and the des-OH derivatives 28 and 34 were only slightly less potent. 4-Methoxybenzenethanamine and 2-methyl-3-nitrophenylacetic acid were employed as starting materials for the synthesis of the 4-(.beta.-aminoethyl)indolones. The ring-opened 3-acylamino analogues 46 and 47 were prepared via nitration of the phenethylamine 43 derived from 4-methoxyphenylacetic acid. The inactive isomeric indolones 38, 39, and 41 were derived from 4-nitrobenzeneethanamine and from indolone-6-acetic acid (13).