[An NMR study of the conformational mobility of 7alpha,8alpha analogues of steroid estrogens].
All the signals in the 1H and 13C NMR spectra of some analogues of 7alpha-methyl-8alpha- and 6-oxa-8alpha-steroid estrogens were completely assigned. Considering the values of nuclear Overhauser effect and vicinal coupling constants, these steroids were shown to exhibit a fast, on the NMR time scale, conformational equilibrium arising due to the inversion of ring B. The conformer populations were obtained from a comparison of the experimental and theoretical values of the dihedral angles and the interproton distances. This conformational equilibrium was shown to depend on the nature of atom in position 6: for the 7alpha-methyl-6-oxa-8alpha analogues of the steroid estrogens, the population of the conformer with the pseudoaxial orientation of the 7alpha-methyl group was observed to be decreased compared with the 7alpha-methyl-8alpha analogue.
S I
SI
Selivanov
A Iu
AIu
Solov'ev
S N
SN
Morozkina
A G
AG
Shavva
D004967:Estrogens / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D012996:Solutions; D013256:Steroids / Q000737:chemistry*
D004967:Estrogens; D012996:Solutions; D013256:Steroids