Author ORCID Identifier
Doctor of Philosophy
Synthetic cathinones and related agents represent an international drug abuse problem, and at the same time an important class of clinically useful compounds. Structure-activity relationship studies are needed to elucidate molecular features underlying the pharmacology of these agents. Illicit methcathinone (i.e., MCAT), the prototype of the synthetic cathinone class, exists as a racemic mixture. Though the differences in potency and target selectivity between the positional and optical isomers of synthetic cathinones and related agents have been demonstrated to have important implications for abuse and therapeutic potential, the two MCAT isomers have never been directly compared at their molecular targets: the monoamine transporters (MATs). Additionally, previous studies have found that the carbonyl oxygen atom can be replaced with a methoxy group, but this results in two chiral centers (i.e., four possible optical isomers for synthesis and evaluation). Here, the individual isomers of MCAT, their racemate, and achiral MCAT analogs were prepared where necessary, and examined in vitro and in silico at the MATs. All agents were active as substrates, with a rank order of potency suggesting that α-position chirality, in either configuration, is favored but not required, with the S(-) configuration slightly preferred. Either chiral center removal approach resulted in a reduction in potency, suggesting both favorable interactions with the α-methyl, and limited bulk tolerance. To further investigate this possibility, docking studies were conducted using homology models of the MATs. Common binding modes were identified that were similar to the binding mode of S(+)amphetamine co-crystallized at drosophila DAT. Taken together, these studies supported our conclusions, as steric hindrance was observed in the α-methyl region of the proposed binding site for the R(+)MCAT isomer.
Inclusion of the original synthetic cathinones among Schedule I controlled substances has driven the clandestine development of a second generation of agents, resulting in an array of new synthetic cathinones diverse in structure and effect.Pyrrolidinophenones are a major constituent of second-generation bath salts. Little is known about their structure-activity relationships. Here, we have synthesized and examined a series of aryl-substituted pyrrolidinophenone analogs, as well as an achiral pyrrolidinophenone analog, utilizing novel synthetic chemistry and an innovative cell-based epifluorescence Ca2+ imaging technique. Herein, we evaluated the neurochemical properties of these novel compounds at the dopamine transporter (DAT), considered to exert a major role in actions of drugs of abuse.
For future structure-activity relationship studies, additional analogs of synthetic cathinone-related agents were produced using novel synthetic approaches, including analogs and isomers of known amphetamine drugs of abuse.
Finally, though much has been learned about the role of the dopamine and serotonin transporters in the mechanisms of action of synthetic cathinones, the role of the norepinephrine transporter is poorly understood. Homology models of the human norephinephrine transporter were built and docking studies conducted to inform the study of MAT ligand selectivity, activity, and binding.
In conclusion, these studies represent progress towards the establishment of comprehensive structure-activity relationships for synthetic cathinones and related agents. Particular emphasis was placed on the SAR of the phenylalkylamine α-carbon in the synthetic cathinone context, and the role of the norepinephrine transporter in their activity.
© Rachel A. Davies, 2019 All Rights Reserved
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Available for download on Wednesday, July 08, 2020
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