Synthesis and structural characterization of an oxaziridine derived from 6-azadiosgenin

•The first spirostanic oxaziridine 18 was synthesized from diosgenin.•Derivatives 12 and 16 are valuable for subsequent modifications on the steroid core.•Cyclization of the isocyanate 15 precursor can be tuned to give mainly 16 or 17.•The stereochemistry of the oxaziridine 18 was established as β-configuration.•X-ray of compound 11a confirmed the preferred α-epoxy orientation at C-5 and C-6. The synthesis of the first spirostanic oxaziridine 18 derived from diosgenin (9) is described, this novel compound is very interesting due to its potential utility in oxaziridine chemistry. Compound 18 was obtained through formation of the 5,6-secoteroid intermediate 12, which after four steps provided 6-azasteroid 16. Notably, depending on the reaction conditions used to carry out the cyclization of the isocyanate 15 to 6-azadiosgenin 16, formation of 16, as the main product, or of 6-azadiene 17 can be favored. Moreover, a mechanistic proposal for the formation of compound 16is discussed. The structures of the products were established by 1D and 2D NMR analysis and in the case of epoxy compound 11a, its structure with α orientation was confirmed by analysis X-ray. [Display omitted]