Steroidal sulphur compounds. Part II. Pyrolysis, absolute configuration, and optical rotatory dispersion of steroidal methyl sulphoxides

Abstract

Chirality at sulphur in (R)- and (S)-4β-methylsulphinyl-5α-cholestane, (R)- and (S)-5α-methylsulphinylcholestane, and 3β-acetoxy-(R)- and (S)-5α-methylsulphinylcholestane has been determined by the pyrolytic method. Base-catalysed epimerization of the 4β-sulphoxides gave (R)- and (S)-4α-methylsulphinyl-5α-cholestane. Chirality at sulphur in 3β-acetoxy-(R)- and (S)-5α-methylsulphinylcholestane was also determined by an interpretation of intramolecular reactions involving the sulphoxide group. Two Cotton effects of opposite sign near 210 and 230 mµ occur in the o.r.d. spectra of the sulphoxides. Their relevance to chirality at sulphur and to restricted rotation about a C–S bond is discussed.