Oxidation with selenium dioxide: the first report of solvent-selective steroidal aromatization, efficient access to 4β,7α-dihydroxy steroids, and syntheses of natural diaromatic ergosterols

Selenium dioxide oxidation of cholesterol reveals a solvent-dependent product selectivity and facile one-pot synthesis of three derivatives, including aromatic analogues of naturally occurring ergosterol. Efficient access to 4β,7α-dihydroxy cholesterol is described. Analogous chemistry of β-sitosterol and diosgenin is also reported. The protocol is found effective to synthesize two diaromatic ergosterol natural products. A brief description of the molecular structures of the representative diaromatic cholesterol derivative and the triacetylated 4β,7α-dihydroxy cholesterol derivative are proven by X-ray crystallography.