Synthesis of steroid compounds part (I): synthesis of novel ethynyl estradiol derivatives

The endogenous estrogens are important female gonad hormones that havemany diverse physiological and pathophysiological actions. Some of clinical trials showed that lower incidence of cardiovascular diseases in premenopausal women is related to the cardio protective effect of estrogens. But, estrogens have been suspected of having carcinogen properties. In order to investigation role of functional groups in specialty of steroid drugs and decreasing (or increasing) estrogenic effects by these groups, we considered in developing new ethynyl estradiols in which simple groups such as carboxylic (CO2H), ester (-CO2Et), amide (-CONH2) and nitrile (-CN) substituted at ethynyl moiety. Two synthesis pathways were suggested to providing the main compounds: In the first path, treatment of Ethynyl estradiol with n-BuLi in THF at -15 C°followed by bubbling anhydrous CO2 (g) through the solution gave the carboxylic compound (-COOH) in 40% yield. Then, ethyl ester compound (-COOEt) was prepared from the carboxylic acid derivative by reaction with absolute ethanol in the presence of acidic catalyst in 70% yield. The amide derivative (-CONH2) was synthesized by passing ammonia (g) from ethanolic solution of ester in reflux state. Its yield was 65%. Treatment of 3, 17 dibenzoyl ethynyl estradiol (was prepared from the reaction of ethynyl estradiol with benzoyl chloride) with n-Buli at -78 °C followed by the addition of cyanogens bromide gave related nitrile compound in 40% yield. The second pathway which was suggested for synthesis of functionalized estradiol derivatives was based on reaction of Ethyl propiolate with 3O-protected estrone in the presence of metal alkalis. All efforts which are accomplished on this reaction along with changing reaction conditions such as alkali reagent (LiNH2, NaNH2, BuLi), different solvents (THF and Ether), reaction temperature (-60 °C to reflux), Amounts of reactants and time of reaction (1 hour to 48 hours) gave no yields higher than 10%. In these efforts, a reaction with quantitative yield was developed for preparing 3- methoxyestrone. All reactions were monitored by TLC (Silicagel 60F 254) in Hexane – EtOAc or Toluene- Acetone. Elucidation of chemical structures of the compounds was made by FT- IR and H NMR.