Ring A Conformation in Steroids 2 -NMR Study of C-2 Monomethyl- and Dimethyl-Substituted 5α-Androstan-3-ones

Article abstract of DOI:10.1002/mrc.1260250814

Ring A proton shifts and couplings and 13C shifts of all carbons are given for 17β-acetoxy-2α-methyl- and 17β-methoxy-2β-methyl-5α-androstan-3-one and 2,2-dimethyl-17β-methoxy-5α-androstan-3-one.It was concluded that the 2α-methyl derivative exists with ring A in a regular chair conformation while the 2β-methyl derivative exists with ring A in an inverted boat conformation with C-2 and C-5 at the bow/stern positions.The data for 2,2-dimethyl-17Β-methoxy-5α-androstan-3-one suggest an equilibrium of these two conformers.KEY WORDS 1H NMR 13C NMR monomethyl/dimethyl 5α-androstan-3-ones Steroid Ring A conformation