Synthetic cannabinoids and their semi-systematic naming developed in Europe – Overview of the chemical diversity and practical guidelines

Abstract

A nomenclature for the naming of synthetic cannabinoids (SC) notified to the EMCDDA was developed. The harmonized names shall convey the structural features of SCs accurately and consistently without the need for a complex systematic name. SCs are the largest group of new psychoactive substances monitored by the EMCDDA and are heterogeneous in their structural makeup. Consistent, concise, and informative naming of SCs has been an ongoing challenge. Over time, several naming conventions have been employed to refer to SCs to avoid the complex but unambiguous systematic IUPAC name, which gives clear hints at the molecular features. Each naming approach aims to make SCs accessible to and recognizable by non-chemists/non-experts/regulators. However, ease of pronunciation and simplicity comes at the cost of detailed information on the structure accessible through the assigned name. All compounds classified as cannabinoids monitored by the EMCDDA were analyzed, and the four building blocks in each SC were identified and abbreviated using consistent letter codes. Inconsistencies in the formerly used names were reviewed and included in developing new consistent letter codes. Rules of the nomenclature and an expanded syntax that combines the letter codes abbreviating the structural features, were developed. The developed nomenclature enables the consistent naming of SCs, which is easy to understand and can be applied by the forensic community, researchers, clinical practitioners, and policy-makers alike. The framework is presented with hands-on guidelines and examples. The chemical diversity of SCs is visualized and made accessible through an electronic data file on all 227 SCs covered. The nomenclature was built on the established letter code system for the molecular building blocks (core, linker, linked group, and tail) implemented by the EMCDDA in 2011 and was expanded to incorporate more structural features through substitution. The main principle of the nomenclature is to reuse previously assigned letter codes, making it easier to recognize the molecular structures. The overall vocabulary is limited by sharing abbreviations of common features across building blocks. Whenever a letter code has to be derived for a new moiety, all previous building blocks and the derived letter codes are taken into account to maximize consistency and minimize complexity. The time of notification of an SC significantly impacts the letter code assigned to the molecular structure. Because of this, the scope of application for the nomenclature has intentionally been limited to SCs which have emerged on the drug market. The developed nomenclature streamlines the process of assigning letter codes to SCs. The nomenclature has already been used to assign names to the most recent SCs detected in the EU. The formerly used name (common name) will continue to be available for reference purposes.