4-[2-(Di-n-propylamino)ethyl]-2(3H)-indolone: a prejunctional dopamine receptor agonist.

4-[2-(Di-n-propylamino)ethyl]-2(3H)-indolone (1c) (SK&F 101468) is a potent and selective prejunctional dopamine receptor agonist. It caused a dose-related inhibition of the constrictor response to electrical stimulation in the isolated perfused rabbit ear artery (EC50 = 100 nM), and this response was antagonized by (S)-sulpiride (KB = 7 nM). Compound 1c did not stimulate or block dopamine-sensitive adenylate cyclase and did not produce stimulation of the central nervous system in rats. It was prepared from (2-methyl-3-nitrophenyl)acetic acid in a multistep sequence based on the Reissert indole synthesis.