Thesis (Ph. D.)--Case Western Reserve University, 2008. / [School of Medicine] Department of Biochemistry. Includes bibliographical references.

While there are a variety of therapeutics that interact with the opioid receptor system, they are not without side effects; including constipation, dysphoria and respiratory depression. A better understanding of the opioid receptor system may yield therapeutic agents with a limited side effect profile. The neoclerodane diterpene, salvinorin A, appears to interact at opioid receptors through a unique mode of action. A better understanding of its interactions with opioid receptors will yield valuable information about the opioid system. In order to probe further how salvinorin A interacts at opioid receptors, a series of novel analogues modified at the C-2 and furan ring were synthesized and evaluated for their ability to interact at opioid receptors. Synthetic methods were identified to modulate the furan ring, including the synthesis of Diels-Alder cycloadducts and phenyl rings derived from a reductive elimination. The cycloadducts are one of the first reported examples of Diels-Alder chemistry being applied to modify a neoclerodane while the phenyl ring analogues are the first to have aromatic rings directly off the salvinorin A core. C-2 sulfonate analogues were found to interact differently then their ester counterparts at opioid receptors while several of the cycloadduct analogues maintained affinity and efficacy demonstrating the furan is not required for opioid receptor activity. These findings demonstrate that salvinorin A is amenable for chemical modification, illustrating its potential as a novel scaffold for the development of opioid ligands.

No description available.

Salvinorin A [(2S,4aR,6aR,7R,9S,10aS,10bR)-9-(acetyloxy)-2-(3-furanyl)-dodecahydro-6a,10b-dimethyl-4,10-dioxo-2H-naptho[2,1-c]pyran-7-carboxylic acid methyl ester] is a trans-neoclerodane diterpene from the leaves of the hallucinogenic Mexican sage Salvia divinorum and has been identified as the principal psychoactive component in this plant of traditional spiritual importance. Salvinorin A is the most potent naturally occurring hallucinogen found so far and is reported to act selectively as a ƒÛ-opioid receptor agonist. Synthetic modification of the natural product has contributed to a number of proposed pharmacophores to identify the key structural features necessary for biological activity and a direct strategy for the asymmetric synthesis of the natural product is desirable since it allows access to a more diverse range of analogues. An ambitious retrosynthetic study of salvinorin A indicated the C(3)-heterosubstituted furan as an appropriate starting material for a Diels-Alder approach towards the ketone ring of the natural product. An expedient and high yielding methodology for the preparation of 3-furylamines is described, allowing the flexible introduction of alkyl substituents in the C(5) position. Optically pure ephedrine isomers have been explored as chiral amine auxiliaries and have been successfully attached as 3-furylamine substituents using the general methodology described. The 3-furylamines are electron rich dienes that are highly reactive towards Diels-Alder cycloaddition reactions with methyl acrylate. Diastereoisomers of the 7-oxanorbornane species methyl 1-methyl-5-oxo-7-oxa-bicyclo[2.2.1]heptane-2-carboxylate were prepared as new compounds from the hydrolysis of Diels-Alder cycloadducts and are functionalised bicyclic intermediates to access the ketone of the natural product. Diels-Alder reactions between the non-racemic (2S)-ephedrine-derived furans and methyl acrylate gave spiro-oxazolidine adducts that underwent hydrolysis to give the desired ketone. X-ray crystallography data for the derivatised cycloadduct established diastereoselectivity in favor of the (1S,4S)-enantiomer, as desired for the asymmetric natural product synthesis. A procedure for the ether cleavage of methyl 1-methyl-5-oxo-7-oxa-bicyclo[2.2.1]heptane-2-carboxylate was required to access the convergent precursor methyl 5-acetoxy-2-methyl-4-oxocyclohex-2-enecarboxylate. Successful C-O cleavage was achieved using Lewis-acid catalysis with BBr3 followed by mixing with the hindered base 2,4,6-collidine to yield methyl 5-hydroxy-2-methyl-4-oxocyclohex-2-enecarboxylate albeit only at high dilution. Acetylation proceeded in excellent yield in the same reaction vessel to give methyl 1-methyl-5-oxo-7-oxa-bicyclo[2.2.1]heptane-2-carboxylate in excellent yield. The devised synthetic pathway is shown to successfully construct the ketone ring of salvinorin A and stereoselectivity for the (1S,4S)-enantiomer can be achieved using the ephedrine derived furans as desired for the asymmetric natural product synthesis. The ƒÔ-lactone ring 6-(furan-3-yl)-5,6-dihydro-4-methyl-3-vinylpyran-2-one was derived from rudimentary precursors as a convergent reagent to introduce the lactone ring of salvinorin A. A short synthesis for the racemic compound is described starting from the aldol reaction between 3-furaldehyde and acetone to give the 3-furfurol, 4-(furan-3-yl)-4-hydroxybutan-2-one in quantitative yield. The 3-furfurol was reacted to form the ƒÑ-bromovinyl ester, 1-(furan-3-yl)-3-oxobutyl 2-bromobut-3-enoate using a deconjugation/esterification protocol with 2-bromobut-3-enoyl chloride. Intramolecular ring closure to the ƒÔ-lactone was achieved using a Reformatsky reaction and dehydration under acidic conditions yielded the racemic convergent precursor 6-(furan-3-yl)-5,6-dihydro-4-methyl-3-vinylpyran-2-one in high yield. A possible strategy for joining the ketone and lactone fragments for the total synthesis of salvinorin A is proposed.

No description available.

Salvinorin A is a non-nitrogenous, selective kappa opioid receptor agonist with potent hallucinogenic properties. Because Salvinorin A has no basic nitrogen, it does not readily adhere to the “message-address” concept of selectivity for the opioid receptors. Therefore, a better understanding of how salvinorin A and its analogs interact with the kappa opioid receptor may shed some light on how salvinorin A obtains its potency and selectivity. The structure-affinity relationships (SAFIR) of salvinorin A and its analogs along with a discussion of the selectivity of the opioid receptors, is presented. A fragment of salvinorin A, methyl-3-acetoxy-4-oxocyclohexanecarboxylate, was synthesized to determine if the B, C and D rings are or are not necessary for binding to the opioid receptors. The fragment was found not to bind to the kappa, delta or mu receptor which reinforces the importance of the B, C and D rings in the binding of salvinorin A to the kappa opioid receptor. Homology models of the kappa, delta and mu opioid receptors were constructed based on inactive bovine rhodopsin, light-activated bovine rhodopsin and the human beta-2 adrenergic receptors. The program MODELLER was also used to construct the kappa opioid receptor. Two comparative molecular field analysis (CoMFA) studies are then presented which compared three different types of alignment methods. The alignment methods employed included a receptor-docked alignment in which the salvinorin A analogs were docked into a model of the kappa opioid receptor using the program GOLD. The docked poses for this alignment were chosen based on their similarity to our postulated model of salvinorin A in the kappa opioid receptor. In our model the furan oxygen forms hydrogen bonds with Q115(2.60) and Y320(7.43), the methoxy oxygen of the C-4 position ester group may form a hydrogen bond with Y312(7.35) and the methyl group of the C-2 position acetoxy moiety forms a hydrophobic interaction with Y313(7.36). These interactions are consistent with mutagenesis studies. The other alignment methods employed were a FlexS alignment and a realignment of the receptor-docked poses using the Fit Atoms function within SYBYL. Only the receptor-docked alignment method resulted in robust and predictive CoMFA models which indicates that the analogs may bind to the kappa opioid receptor in a similar but non-identical way. In addition, information from the CoMFA models based on the receptor-docked alignment led to a postulated binding mode for a set of amine analogs of salvinorin A which were not part of the original data set. Docking studies have the positively charged C-2 position amine group interacting with E209(XL2.49) while the furan oxygen and C-4 position ester group interacts with the same residues as in our model of salvinorin A in the kappa opioid receptor. The studies presented here not only support our postulated model of salvinorin A binding to the kappa opioid receptor but may also explain the trend of the beta epimers of the amine analogs to have a higher affinity than the corresponding alpha epimers. Site-directed mutagenesis studies could provide data to support or refute the postulated models of the amines docked in the kappa opioid receptor presented here.

Salvia divinorum is a hallucinogenic sage used to treat illness by the Mazatec Indians of Mexico. Salvinorin A (1a), a neoclerodane diterpenoid isolated from the plant, is a potent, selective agonist at the kappa opioid receptor (KOR), and is the first non-nitrogenous opioid. The plant is used recreationally as a hallucinogen, but is unpopular due to its dysphoric effects. 1a has been prohibited in Australia under an invalid systematic name. An early report of psychoactive alkaloids in S. divinorum proved to be irreproducible. Similarly, tests in mice suggesting the presence of psychoactive compounds other than 1a were confounded and therefore unreliable. In this work, an improved isolation method for 1a was developed, using filtration through activated carbon to decolourise the crude extract. Six new diterpenoids were isolated: salvinorins D–F (1d–1f) and divinatorins A–C (28a–28c). Five known terpenoids not previously reported from this species were also isolated. The structure–activity relationships of 1a were evaluated via selective modifications of each functional group. Useful synthetic methods are reviewed, including the first thorough review of furanolactone hydrogenations. Testing of the derivatives at the KOR suggests that the methyl ester and furan ring of 1a are required for activity, but that the lactone and ketone functionalities are not. Other compounds from S. divinorum did not bind to the KOR, suggesting that 1a is the plant’s active principle.

<p>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. </p><p>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-HT_1Areceptor and one agonist with 29 fold greater selectivity over the serotonin 5-HT_1Areceptor. Thus the present series constitutes a starting point for developing highly selective ligands for the 5-HT₇ receptor. </p><p>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 <i>Pseudomonas fluorescens</i> was identified as having stereoselectivity high enough to generate a % <i>ee </i>value above 98%. We have also developed a route for the introduction of a hydroxyl functionality in the γ position of α,β-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.</p>

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 γ position of α,β-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.