The k-opioid receptor (KOR)-dynorphin system has been implicated in the control of affect, cognition, and motivation, and is thought to be dysregulated in mood and psychotic disorders, as well as in various phases of opioid dependence. KOR agonists exhibit analgesic effects, although the adverse effects produced by some KOR agonists, including sedation, dysphoria, and hallucinations, have limited their clinical use. Interestingly, KOR-mediated dysphoria, assessed in rodents as aversion, has recently been attributed to the activation of the p38 mitogen-activated protein kinase pathway following arrestin recruitment to the activated KOR. Therefore, KOR-selective G protein-biased agonists, which do not recruit arrestin, have been proposed to be more effective analgesics, without the adverse effects triggered by the arrestin pathway. As an initial step toward identifying novel biased KOR agonists, we applied a multifaceted screening strategy utilizing both in silico and parallel screening approaches. We identified several KORselective ligand scaffolds with a range of signaling bias in vitro. The arylacetamide-based scaffold includes both G protein-and b-arrestin-biased ligands, while the endogenous peptides and the diterpene scaffolds are G protein biased. Interestingly, we found scaffold screening to be more successful than library screening in identifying biased ligands. Many of the identified functionally selective ligands are potent selective KOR agonists that are reported to be active in the central nervous system. They therefore represent excellent candidates for in vivo studies aiming at determining the behavioral effects mediated by specific KORmediated signaling cascades.

Salvinorin A, the most potent naturally occurring hallucinogen, has gained increasing attention since the κ-opioid receptor (KOR) was identified as its principal molecular target by us (Roth et al, PNAS, 2002). Here we report the design, synthesis and biochemical characterization of novel, irreversible, salvinorin A-derived ligands suitable as active state probes of the KOR. Based on prior substituted cysteine accessibility and molecular modeling studies, C315 7.38 was chosen as a potential anchoring point for covalent labeling of salvinorin A-derived ligands. Automated docking of a series of potential covalently-bound ligands suggested that either a haloacetate moiety or other similar electrophilic groups could irreversibly bind with C315 7.38 . 22-thiocyanatosalvinorin A (RB-64) and 22-chlorosalvinorin A (RB-48) were both found to be extraordinarily potent and selective KOR agonists in vitro and in vivo. As predicted based on molecular modeling studies, RB-64 induced wash-resistant inhibition of binding with a strict requirement for a free cysteine in or near the binding pocket. Mass spectrometry (MS) studies utilizing synthetic KOR peptides and RB-64 supported the hypothesis that the anchoring residue was C315 7.38 and suggested one biochemical mechanism for covalent binding. These studies provide direct evidence for the presence of a free cysteine in the agonist-bound state of KOR and provide novel insights into the mechanism by which salvinorin A binds to and activates KOR.Salvinorin A, the active ingredient of the hallucinogenic plant Salvia divinorum, is the most potent known naturally-occurring hallucinogen (1,2). In 2002, we discovered that the κ-opioid receptor (KOR) was the molecular target for the actions of salvinorin A in vitro (3). Studies with KOR knock-out mice (4) unequivocally demonstrated that the KOR was also the site of † This research was supported in part by NIH R01DA017204 (to B . NIH Public Access Author ManuscriptBiochemistry. Author manuscript; available in PMC 2010 July 28. Published in final edited form as:Biochemistry. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript action of salvinorin A in vivo-a finding which has been widely replicated (see (5) and (6) for reviews). Subsequently, salvinorin A emerged as an attractive lead compound for drug discovery and during the past few years, hundreds of salvinorin A derivates have been synthesized (6). Some of these analogues present interesting pharmacological profiles, from full KOR agonist to partial δ-opioid receptor (DOR) or µ-opioid receptor (MOR) agonists and antagonists (7) (8) (9) (10) (11). However, most of the hundreds of analogues displayed decreased affinity (or even no affinity) to KOR. The present challenge now is to use the knowledge about salvinorin A-KOR interactions (12) (13) to design unique salvinorin A derivatives with novel pharmacological profiles and therapeutic potential. In recent years, covalently-bound ligands emerged as a new class of receptor ligands with unique pharmacologi...

To study drug-receptor interactions, new thio-derivatives of salvinorin A, an extremely potent natural kappa-opioid receptor (KOR) agonist, were synthesized. Obtained compounds were examined for receptor binding affinity. Analogs with the same configuration at carbon atom C-2 as in natural salvinorin A showed higher affinity to KOR than their corresponding epimers.

Novel semisynthetic analogs of salvinorin A, a full agonist having extraordinary affinity as well as selectivity for the κ-opioid receptor (KOR), were obtained in good yields. The derivatives are remarkable for their unusual and unique hemiacetal structure in the salvinorin series of compounds. The formation of the hemiacetal occurs with epimerization at C-12, thus preserving the original configuration of salvinorin A. The dimethyl ester derivative of the hemiacetal was found to have an affinity for both KOR and MOR (μ-opioid receptor).Keywords salvinorin A; KOR ligands; hemiacetal; dual afinity Salvinorin A, a secondary metabolite isolated from the leaves of Salvia divinorum, is a neoclerodane diterpenoid with a strong hallucinogenic activity. It has been shown to have high affinity and selectivity for KOR. 1 Salvinorin A represents an attractive lead compound for drug development due to its strong effects on human mood and low toxicity. In the last two years numerous derivatives and analogs of salvinorin A were synthesized showing a broad range of KOR affinities. 2 Synthesis of new analogs of salvinorin A is important for generating structure-receptor affinity data and for design of agents with therapeutic potential. Some of the chemical modifications of salvinorin A have produced analogs with changed pharmacological profiles from full κ-agonist to partial δ-or μ-agonists or antagonists. 2i,2m,3 Recently, modifications of the furan ring yielded the first analogs with κ-antagonistic activity. 2bIn this paper we report the synthesis of the hemiacetal (2) and its derivatives starting from salvinorin A. Refluxing 1 with 5% aqueous KOH surprisingly gave only one product according to thin-layer chromatography. 4 (Scheme 1).

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hormones hormones U 1000 47 -194 Prostanoids. Part 82. Synthesis of Key Precursors of 9-LO Thromboxans -[synthesis of pyranoside (I) and enedione (II) as potential building blocks for the preparation of 9-LO thromboxanes]. -(AKHMETVALEEV, R. R.; BIKBULATOV, R. V.; BELOGAEVA, T. A.; AKBUTINA, F. A.; MIFTAKHOV, M. S.; Russ.

hormones hormones U 1000 -193Prostanoids. Part 81. Synthesis of (±)-2-Decarboxy-2-ethyl-19,20dinor-18-carboxyprostaglandin E 1 (II).--(AKHMETVALEEV, R. R.; BIKBULATOV, R. V.; BELOGAEVA, T. A.; AKBUTINA, F. A.; MIFTAKHOV, M. S.; Russ.