Crystallographic investigations of select cathinones: emerging illicit street drugs known as `bath salts'

Abstract

The name `bath salts', for an emerging class of synthetic cathinones, is derived from an attempt to evade prosecution and law enforcement. These are truly illicit drugs that have psychoactive CNS (central nervous system) stimulant effects and they have seen a rise in abuse as recreational drugs in the last few years since first having been seen in Japan in 2006. The ease of synthesis and modification of specific functional groups of the parent cathinone make these drugs particularly difficult to regulate. MDPV (3,4-methylenedioxypyrovalerone) is commonly encountered as its hydrochloride salt (C16H21NO3·HCl), in either the hydrated or the anhydrous forms. This `bath salt' has various names in the US,e.g.`Super Coke', `Cloud Nine', and `Ivory Wave', to name just a few. We report here the structures of two forms of the HCl salt, one as a mixed bromide/chloride salt, C16H22NO3+·0.343Br−·0.657Cl−[systematic name: 1-(benzo[d][1,3]dioxol-5-yl)-2-(pyrrolidin-1-ium-1-yl)pentan-1-one bromide/chloride (0.343/0.657)], and the other with the H7O3+cation, as well as the HCl counter-ion [systematic name: hydroxonium 1-(benzo[d][1,3]dioxol-5-yl)-2-(pyrrolidin-1-ium-1-yl)pentan-1-one dichloride, H7O3+·C16H22NO3+·2Cl−]. This is one of a very few structures (11 to be exact) in which we have a new example of a precisely determined hydroxonium cation. During the course of researching the clandestine manufacture of MDPV, we were surprised by the fact that a common precursor of this illicit stimulant is known to be the fragrant species piperonal, which is present in the fragrances of orchids, most particularly in the case of the vanilla orchid. We found that MDPV can be made by a Grignard reaction of this heliotropin. This may also explain the unexpected appearance of the bromide counter-ion in some of the salts we encountered (C16H21NO3·HBr), one of which is presented here [systematic name: 1-(benzo[d][1,3]dioxol-5-yl)-2-(pyrrolidin-1-ium-1-yl)pentan-1-one bromide, C16H22NO3+·Br−]. Complexation of MDPV with a forensic crystallizing reagent, HAuCl4, yields the tetrachloridoaurate salt of this drug, (C16H22NO3)[AuCl4]. The heavy-metal complexing agent HAuCl4has been used for over a century to identify common quarternary nitrogen-containing drugsviamicroscopic identification. Another street drug, called ethylone (3,4-methylenedioxyethylcathinone), is regularly sold and abused as its hydrochloride salt (C12H15NO3·HCl), and its structure is herein described (systematic name:N-{1-[(benzo[d][1,3]dioxol-5-yl)carbonyl]ethyl}ethanaminium chloride, C12H16NO3+·Cl−). Marketed and sold as a `bath salt', `plant feeder', or `cleaning product', this drug is nothing more than a slight chemical modification of the banned drug methylone (3,4-methylenedioxymethcathinone). As with previously popular synthetic cathinones, the abuse of ethylone has seen a recent increase due to regulatory efforts on previous generations of cathinones that are now banned.