6,7,8,9-Tetrahydro-N,N-di-n-propyl-3H-benzindol-8-amines. Derivatives as potent and orally active serotonin 5-HT1A receptor agonists.

Derivatives and isosteric derivatives of the potent 5-HT1A agonist 8-(di-n-propylamino)-6,7,8,9- tetrahydro-3H-benz[e]indole-1-carbaldehyde (5) were prepared and evaluated in vivo and in vitro for serotonergic and dopaminergic activity. The 1-cyano analog 8 was found to be almost equipotent to 5 and the previously described 2-cyano derivative 6, while a 1-chloro and 1-(1,1,1-trifluoroethyl) substituent (9 and 10, respectively) formed less potent derivatives. The isosteric 6,7,8,9-tetrahydro-1H-benz[g]indoles 4 and 12-15 showed surprisingly low affinity or activity at both serotonergic and dopaminergic systems. The interpretations of these results by means of drug-receptor interactions at the 5-HT1A subtype are discussed. Compounds 6 and 8 were found to have high oral bioavailability in the rat (63% and 54%, respectively).