Optimization of a benzyl piperazine pharmacophore produced N-acyl-4-indanyl-piperazines that bind with high affinity to melatonergic MT2 receptors.(R)-4-(2, 3-dihydro-6-methoxy-1H- inden-1-yl)-N-ethyl-1-piperazine-carboxamide fumarate (13) is a water soluble, selective MT2 agonist, which produces advances in circadian phase in rats at doses of 1–56 mg/kg that are no different from those of melatonin at 1 mg/kg. Unlike melatonin, 13 produced ...