Synthesis and biological evaluation of C-2 halogenated analogs of salvinorin A.
Bioorganic & medicinal chemistry letters October 1, 2010 David Y W Lee, Lu Yang, Wei Xu et al.
Salvinorin A, the main active ingredient of Salvia divinorum, is a potent and selective κ opioid receptor (KOPR) agonist. Researchers synthesized a series of C-2 halogenated analogs of salvinorin A as molecular probes to investigate the binding pocket at the C-2 position, particularly the effects of α versus β configuration. Binding and functional studies showed that β isomers generally bind better than α isomers, except for iodinated analogs. None of the C-2 halogenated analogs improved KOPR binding affinity compared to the parent compound. Functional assays characterized one analog, 6b, as a partial agonist with a maximum effect of 46% of the full agonist U50,488H at 250 nM. Affinity to the kappa receptor increased with atomic radius (I>Br>Cl>F), consistent with halogen bonding interactions.