Solvent effects in the nuclear magnetic resonance spectra of steroidal ketones

Abstract

The chemical shifts in deuteriochloroform and in benzene of the 19-methyl groups in a series of 1-oxo-, 4-oxo-, and 1,4-dioxo-steroids have been studied. As expected, the 19-methyl in 1-oxo-5β-steroids shows a slight negative solvent shift, Δ(CDCl₃/C₆H₆). Based on these results, ring A in 4β,6β-epoxy-1-oxo-steroids [(III) and (VI)] is assigned a boat conformation, whereas for a 4β-acetoxy-5β-hydroxy-1-oxo-steroid (XIV) the solvent shifts indicate a chair conformation for ring A. Effects of polar substituents such as hydroxy-groups and epoxide rings on the solvent shifts of the 19-methyl have also been examined.