title: Exploration of synthetic approaches and pharmacological evaluation of PNU-69176E and its stereoisomer as 5-HT2C receptor allosteric modulators.
abstract: Allosteric modulators of the serotonin (5-HT) 5-HT(2C) receptor (5-HT(2C)R) present a unique drug design strategy to augment the response to endogenous 5-HT in a site- and event-specific manner with great potential as novel central nervous system probes and therapeutics. To date, PNU-69176E is the only reported selective positive allosteric modulator for the 5-HT(2C)R. For the first time, an optimized synthetic route to readily access PNU-69176E (1) and its diastereomer 2 has been established in moderate to good overall yields over 10 steps starting from commercially available picolinic acid. This synthetic approach not only enables a feasible preparation of a sufficient amount of 1 for use as a reference compound for secondary pharmacological studies, but also provides an efficient synthesis of key intermediates to develop novel and simplified 5-HT(2C)R allosteric modulators. Compound 1 and its diastereomer 2 were functionally characterized in Chinese hamster ovary (CHO) cells stably transfected with the 5-HT(2C)R using an intracellular calcium (Ca(i) (2+)) release assay. Compound 1 demonstrated efficacy and potency as an allosteric modulator for the 5-HT(2C)R with no intrinsic agonist activity. Compound 1 did not alter 5-HT-evoked Ca(i) (2+) in CHO cells stably transfected with the highly homologous 5-HT(2A)R. In contrast, the diastereomer 2 did not alter 5-HT-evoked Ca(i) (2+) release in 5-HT(2A)R-CHO or 5-HT(2C)R-CHO cells or exhibit intrinsic agonist activity.
authors.affiliation: Chemical Biology Program, Department of Pharmacology and Toxicology, University of Texas Medical Branch, 301 University Boulevard, Galveston, Texas 77555, USA.
authors.forename: Chunyong
authors.initials: C
authors.lastname: Ding
authors.forename: Nicole M
authors.initials: NM
authors.lastname: Bremer
authors.forename: Thressa D
authors.initials: TD
authors.lastname: Smith
authors.forename: Patricia K
authors.initials: PK
authors.lastname: Seitz
authors.forename: Noelle C
authors.initials: NC
authors.lastname: Anastasio
authors.forename: Kathryn A
authors.initials: KA
authors.lastname: Cunningham
authors.forename: Jia
authors.initials: J
authors.lastname: Zhou
mesh_terms: D000494:Allosteric Regulation / Q000187:drug effects / Q000502:physiology; D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D006224:Cricetinae; D003412:Cricetulus; D004353:Drug Evaluation, Preclinical / Q000379:methods; D005697:Galactosides / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology*; D006801:Humans; D010880:Piperidines / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology*; D044405:Receptor, Serotonin, 5-HT2C / Q000378:metabolism* / Q000502:physiology; D013237:Stereoisomerism
chemical_list: D005697:Galactosides; D010880:Piperidines; D044405:Receptor, Serotonin, 5-HT2C; C475727:methyl-7-chloro-6,7,8-trideoxy-6-(((4-undecyl-2-piperidinyl)carbonyl)amino)-1-thiomonohydrochloride (2S-cis), L-threo-alpha-D-galacto-octopyranoside; D002118:Calcium