Identification and characterization of a putative new psychoactive substance, 2‐(2‐(4‐chlorophenyl)acetamido)‐3‐methylbutanamide, in Spain

The term ‘new psychoactive substances’ (NPS) refers to synthetically changed natural compounds or newly designed compounds intended to elicit a psychotropic response such as stimulation, hallucination or sedation. According to the European Monitoring Centre for Drugs and Drug Addiction of the European Union, more than 560 NPS are currently being monitored, and 98 of these substance were reported for the first time in 2015. Despite that, there are still many NPS that are not being monitored, and therefore their health effects are not yet studied. Hence, many cases of intoxication and death related to NPS have been reported in the past few years, highlighting the public health risks of these substances. One of the challenges of monitoring NPS is the continuous structural evolution to evade regulation, so when one substance is banned or controlled, several new compounds replace it in the market. NPS are usually found with various appearances, like incenses, bath salts, herbal blends or party pills, sold through an unregulated market, different websites or smart-shops. These products are typically known as ‘legal highs’. Synthetic cannabinoids, synthetic cathinones and amphetamines constitute the largest groups of NPS, although opioids, tryptamines, benzodiazepines, piperazines and phenethylamines are also common. Synthetic cathinones and amphetamines are sold as replacements for stimulants, and have been reported in pills, crystal and sniff powder. Synthetic cannabinoids are commonly sold as herbal blends or spices, replacing cannabis. Forensic laboratories, universities, research institutes, public health centres and law enforcement agencies play an important role in monitoring these types of substances, which are also encountered in customs seizures and medical emergencies. Various analytical approaches have been reported for the analysis of NPS in legal highs samples. Gas chromatography coupled to mass spectrometry (GC–MS) using electron ionization (EI) is a fast and reliable technique for the identification of these compounds based on the use of spectral libraries. However, fragmentation spectra of novel NPSmay not be available. Moreover, some of these compounds are non-volatile and thermolabile, requiring additional derivatization steps in GC–MS analysis. Liquid chromatography (LC) coupled to high-resolution MS (HRMS) has proven to be a powerful technique for the screening of NPS in legal highs samples. Moreover, HRMS allows screening analyses without reference standards being available (tentative identification). HRMS/MS also has potential application in the compound structural elucidation of unknown substances by using accurate-mass fragmentation data. As complementary tools to HRMS instruments, additional spectroscopic techniques can be used for the unequivocal characterization of NPS. Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy are useful for a fast evaluation of molecules, identifying functional groups without destroying the sample and with reasonable running costs. Nuclear magnetic resonance (NMR) spectroscopy has proved to be one of the most powerful techniques for the structural elucidation and characterization of organic molecules, and has been applied to the identification and characterization of synthetic cannabinoids and synthetic cathinones. X-ray crystallography, especially single-crystal X-ray diffraction, allows an unequivocal characterization of the structure of a molecule, but only if the compound can be formed as X-ray-suitable crystals. Thus, the combination of spectroscopic and mass spectrometric techniques provides a versatile workflow for structural elucidation, characterization and identification of unknown substances. The aim of the work reported here was the determination of the main compound present in a crystal sample from an anonymous Spanish consumer. The structure of a new designer drug derivate was elucidated after an exhaustive analysis using various analytical techniques. Characterization of the molecule was performed by GC–MS, LC-HRMS using hybrid quadrupole time-of-flight (QTOF) mass analyser, NMR and single-crystal X-ray diffraction. Additionally, melting point determination, FTIR and ultraviolet