The naphyrone story: The alpha or beta-naphthyl isomer?

Naphyrone (naphthylpyrovalerone, O-2482) has been recently advertised for purchase on a number of websites. This compound has been viewed as a so-called 'legal high' and was classified as a controlled drug under the UK Misuse of Drugs Act 1971 in mid-July 2010. So far, naphyrone is commonly equated with 1-naphthalen-2-yl-2-pyrrolidin-1-yl-pentan-1-one (β-naphyrone) but analytical characterization of two naphyrone samples revealed the existence of a novel isomer consistent with 1-naphthalen-1-yl-2-pyrrolidin-1-yl-pentan-1-one (α-naphyrone). Analyses of both α- and β-naphyrone were carried out using gas chromatography ion trap (EI/CI) mass spectrometry and 1D/2D nuclear magnetic resonance spectroscopy. This provides the first report of α-naphyrone in the scientific literature and the ability to differentiate it from the β-isomer should be of interest to forensic and clinical communities.