Synthesis of Molecular Probes for Exploring the Human Consciousness, 5-HT7 Ligands and Salvinorins

Abstract: In this study, we have addressed the serotonergic and the opioid system within the CNS. Both systems are of outmost importance in the etiology of disease states, especially mental disorders. In our investigation of the serotonergic system, we have synthesized novel enantiomerically pure 6-aryl-3-amino- and 8-aryl-3-aminochromans as ligands for the 5-HT7 receptor. One reason for the lack of understanding of the physiological functionality of the serotonin 5-HT7 receptor, the most recently discovered member of the serotonin receptor family, is the absence of partial agonists and agonists. In this series, we have identified partial agonists with more than189 fold selectivity over the 5-HT1A receptor and one agonist with 29 fold greater selectivity over the serotonin 5-HT1A receptor. Thus the present series constitutes a starting point for developing highly selective ligands for the 5-HT7 receptor. In our investigation of the opioid system, our focus has been on the natural product salvinorin A, which is a highly selective kappa opioid receptor agonist. In the total synthesis of salvinorin A, we have accomplished the synthesis of a key intermediate, 6-(3-furyl)-4-methyl-5,6-dihydro-pyran-2-one via ring closing metathesis. Furthermore, synthetic methodologies have been developed as a part of the total synthesis. Several lipases have been screeened for their ability to generate enantiomerically pure 1-(3-Furyl)-3-buten-1-ol via bio-catalyzed hydrolysis of the corresponding acetate. The lipase from Pseudomonas fluorescens was identified as having stereoselectivity high enough to generate a % ee value above 98%. We have also developed a route for the introduction of a hydroxyl functionality in the ? position of ?,?-unsaturated cyclic ketones by the regioselective oxidation of 1-silyloxy-1,3-dienes using dimethyldioxirane. We have initiated the investigation of the pharmacophore responsible for the kappa opioid activity by synthesizing simplified analogues of salvinorin A. A synthetic route providing easy access to simplified analogues of salvinorin A have been established.