Conformational aspects of some ring Aα-acetoxy-ketones in the cholestane series

Abstract

In contrast to 2α-acetoxy-3-oxo- and 3α-acetoxy-2-oxo-5α-cholestane, which gave n.m.r. and c.d. spectra consistent with a chair conformation of ring A, the corresponding 5α-hydroxy-derivatives have spectral data indicative of twisted conformations of ring A. Conversely, 2β-acetoxy-5-hydroxy-3-oxo-5α-cholestane has ring A in the same boat-like conformation as the corresponding 5-deoxy-compound. 3β-Acetoxy-2-oxo- and 3β-acetoxy-5-hydroxy-2-oxo-5α-cholestane have ring A in the chair conformation.