Chiral separation of methylone and pentedrone and synthesis of key metabolites: toward a comprehensive understanding of synthetic cathinone toxicity

Background: Synthetic cathinones, such as methylone and pentedrone, are new psychoactive substances that pose a significant health threat due to their widespread accessibility and limited toxicological data available [1]. For a deeper understanding of their toxicological effects, it is essential to consider synthetic cathinones as a whole, including their stereochemistry and structural modifications resulting from biotransformation. Being chiral compounds, their enantiomers constitute individual distinct chemical entities that can exhibit different properties, as demonstrated in previous studies [2,3]. Likewise, metabolites should be considered alongside the parent compounds, as they may also contribute to overall activity or toxicity [4]. Despite the metabolism of synthetic cathinones being well reported, involving pathways such as β-keto reduction and N-demethylation [5,6], the specific effects of their metabolites remain largely underexplored. Objective: The primary aim of this study is to investigate the influence of chirality and metabolism on the toxicological profile of methylone and pentedrone. Specifically, this work seeks to isolate both single enantiomers and to synthesize key metabolites. Methods: Semi-preparative enantioseparation and evaluation of enantiomeric purity were conducted by chiral liquid chromatography (cLC) using amylose-based columns. Dihydro-metabolites were synthesized by β-keto reduction of parent drugs, while nor-metabolites by 5 synthetic steps starting from benzaldehyde derivatives. Structure elucidation was performed by spectroscopic methods (1H- and 13C-NMR and IR). Results: Optimized cLC conditions provided Rs and α values above 1.5 and 1.2, respectively. Enantiomers were obtained with enantiomeric ratios over 95% and recovery rates over 60%. Metabolites and intermediates were synthesized with yields of 48-94%. Conclusions: Both enantiomers of methylone and pentedrone were isolated with high enantiomeric purity. Dihydro- and nor-metabolites were successfully synthesized, with good yields. Isolated enantiomers and synthesized metabolites will serve as key tools in future metabolomic studies to evaluate the enantioselective effects and the role of metabolites toward a comprehensive understanding of synthetic cathinones toxicity.