Identification of steroid isoxazole isomers marketed as designer supplement

The product Orastan-A from Gaspari Nutrition was analyzed for its steroid content. According to the labeling, it is supposed to contain "5a-Androstano[2,3-c]furazan-17b-tetrahydropyranol ether", also called furazadrol-THP ether. The GC-MS analyses of the liberated steroids (after extraction from the capsule matrix and cleavage of the THP ether, TMS-derivative and underivatized) revealed mass spectra of two components, both inconsistent with the labeling. Thus, the steroids were characterized by different analytical techniques such as mass spectrometry, nuclear magnetic resonance spectroscopy and X-ray crystal structure analysis. They were identified as 17beta-hydroxyandrostano[3,2-c]isoxazole and -[2,3-d]isoxazole.