The molecular structure of 3-methoxy-9 (10 leads to 19) abeo- 1,3, 5, (10)-estratrien-17-one

The crystal and molecular structure of 3-methoxy-9(10 leads to 19)abeo-1,3,5(10)-estratrien-17-one has been determined by X-ray analysis in order to ascertain the configuration at C(9). The seven-membered B-ring has a chair conformation and this causes the molecule to bow towards the alpha-face rather than towards the beta-face as in estradiol.