Synthesis and in vitro and in vivo functional studies of ortho-substituted phenylpiperazine and N-substituted 4-N-(o-methoxyphenyl)aminopiperidine analogues of WAY100635.

WAY100635 (2), N-[2-[4-(2-methoxyphenyl)-1-piperazinyl]ethyl]-N-(2-pyridinyl)cyclohe xanecarboxamide, is a silent serotonin 5-HT(1A) antagonist, which is now widely used to study the 5-HT(1A) receptor both in vivo and in vitro. In this paper, we describe the synthesis and in vitro (5-HT(1A) affinity and pA(2) values at guinea pig ileum strips) and in vivo (hypothermia and ultrasonic vocalization) pharmacology at the serotonin 5-HT(1A) receptor of several closely related analogues of 2. Test compounds 12 and 14, in which the arylpiperazine moiety of 2 has been replaced by an arylaminopiperidine moiety, showed no affinity or antagonistic activity at the 5-HT(1A) receptor. Substitution of the o-methoxy group of 2 by larger fluoroalkoxy or sulfonyloxy substituents did not alter the in vitro or in vivo pharmacology to any great extent; in vivo both the fluoropropyl analogue 5 and the triflate analogue 7 are equipotent to WAY100635 itself. The O-desmethyl analogue 3 proved to be the most potent antagonist at the serotonin 5-HT(1A) postsynaptic receptor sites in this series.