A re‐examination of the synthesis and some properties of the in vitro metabolite, N ‐hydroxyphenmetrazine

The reported synthesis of N ‐hydroxyphenmetrazine from phenmetrazine by the action of m ‐chloroperbenzoic acid could not be repeated. When the synthetic procedure was modified N ‐hydroxyphenmetrazine was obtained in low yield. The product had different properties from those claimed previously, but was identical to metabolically produced N ‐hydroxyphenmetrazine. It was characterized by means of thin‐layer chromatography, combined gas chromatography and mass spectrometry, preparation of a t ‐butyldimethylsilyl derivative and oxidation to a mixture of nitrones. Mass spectrometry was also used to characterize these derivatives.