| Estrogen replacement therapy can prevent or treat a variety of symptoms ofmenopause or disorders caused by deficiency of estrogen. However, it could result in the increasing probality of breast and uterine cancer at the same time, so, it is essential to develop estrogens which have low estrogenic activity whereas function as estrogen in certain organs. Compared with 17 -estradiol, 17 α -estradiol has very low estrogenic activity, but not much reseach work about its preparation has been done. In this paper, some exploratory research as follows involving the preparation of 17 a -estradiol was carried out.1. Preparating model compounds to study the mechanism of configurational conversion,it wal found that the 3-tosylate of estradiol 3,17 -ditosylate wal difficult to undergo acetolysis whereas the 17-tosylate could undergo El.elimination or rearrangment-elimination through a carbon cation intermidiate to produce a mixture which could not be separated by normal methods, and could undergo a Svi2 reaction through a bimolecular transition term to produce the intermediates with converted configuration. The structures of the intermediates were identified by 1H-NMR, 13C-NMR and NOEDS.The research of the mechanism on configurational conversion in this paper has not been reported elsewhere.2. The reaction condition of configurational convertion in literature were changed to DMF-KOAc-HOAc in the course of the research . It resulted to increasing the reaction speed and the ratio of the inversion-configuration compounds.3. Estrone, as the starting material, underwent reduction .esterification, acetolysis,hydrolysis, column chromatography and recrystalization, producing 17 α -estradiol with a total yield of 20%, whose [ α ]Dt' is identical with that of standard and %d.e.is 100% determined by HPLC.
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