title: The 2-alkyl-2H-indazole regioisomers of synthetic cannabinoids AB-CHMINACA, AB-FUBINACA, AB-PINACA, and 5F-AB-PINACA are possible manufacturing impurities with cannabimimetic activities.
abstract: Indazole-derived synthetic cannabinoids (SCs) featuring an alkyl substituent at the 1-position and l-valinamide at the 3-carboxamide position (e.g., AB-CHMINACA) have been identified by forensic chemists around the world, and are associated with serious adverse health effects. Regioisomerism is possible for indazole SCs, with the 2-alkyl-2H-indazole regioisomer of AB-CHMINACA recently identified in SC products in Japan. It is unknown whether this regiosiomer represents a manufacturing impurity arising as a synthetic byproduct, or was intentionally synthesized as a cannabimimetic agent. This study reports the synthesis, analytical characterization, and pharmacological evaluation of commonly encountered indazole SCs AB-CHMINACA, AB-FUBINACA, AB-PINACA, 5F-AB-PINACA and their corresponding 2-alkyl-2H-indazole regioisomers. Both regioisomers of each SC were prepared from a common precursor, and the physical properties,1H and13C nuclear magnetic resonance spectroscopy, gas chromatography-mass spectrometry, and ultraviolet-visible spectroscopy of all SC compounds are described. Additionally, AB-CHMINACA, AB-FUBINACA, AB-PINACA, and 5F-AB-PINACA were found to act as high potency agonists at CB1(EC50= 2.1-11.6 nM) and CB2(EC50= 5.6-21.1 nM) receptors in fluorometric assays, while the corresponding 2-alkyl-2H-indazole regioisomers demonstrated low potency (micromolar) agonist activities at both receptors. Taken together, these data suggest that 2-alkyl-2H-indazole regioisomers of AB-CHMINACA, AB-FUBINACA, AB-PINACA, and 5F-AB-PINACA are likely to be encountered by forensic chemists and toxicologists as the result of improper purification during the clandestine synthesis of 1-alkyl-1H-indazole regioisomers, and can be distinguished by differences in gas chromatography-mass spectrometry fragmentation pattern.
authors.affiliation: School of Chemistry, The University of Sydney, Sydney, NSW 2006 Australia.
authors.forename: Mitchell
authors.initials: M
authors.lastname: Longworth
authors.affiliation: School of Chemistry, The University of Sydney, Sydney, NSW 2006 Australia.|Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA USA.
authors.forename: Samuel D
authors.initials: SD
authors.lastname: Banister
authors.affiliation: Department of Chemistry, Stanford University, Stanford, CA USA.
authors.forename: James B C
authors.initials: JBC
authors.lastname: Mack
authors.affiliation: School of Medical Sciences, The University of Auckland, Auckland, New Zealand.
authors.forename: Michelle
authors.initials: M
authors.lastname: Glass
authors.affiliation: Department of Biomedical Sciences, Macquarie University, Sydney, Australia.
authors.forename: Mark
authors.initials: M
authors.lastname: Connor
authors.affiliation: School of Chemistry, The University of Sydney, Sydney, NSW 2006 Australia.|Faculty of Health Sciences, The University of Sydney, Sydney, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Kassiou
keywords: 2H-indazole regioisomer; CHMINACA; FUBINACA; Indazole synthetic cannabinoid; Manufacturing impurity with cannabinoid activity; PINACA