| 摘要 |
The invention comprises steroids of the formula <FORM:1085612/C2/1> (wherein R1 is alkyl of at most 4 carbon atoms, R2 is hydrogen or acyl, R3 is keto, H(OH) or H(O acyl) and C6-C7 is saturated or unsaturated) and their preparation by reducing the corresponding 3-keto compounds and, if desired, esterifying the products; and the preparation of the D 4,6-compounds by brominating the corresponding D 5-3b -hydroxy or -3b -acyloxy compounds followed by dehydrobromination. Starting from the 3,20-diketo compounds the 20-keto group may be reduced together with the 3-keto group or only the 3-keto group may be reduced either by selective reduction or by protection, e.g. ketalization, of the 20-keto group. The products may be esterified in the 3- and/or 20-position. 20-Ketones may be reduced to 20-ols. Examples are given. 16a - Ethyl - pregn - 4 - ene - 3,20 - dione 20 - ethyleneketal is prepared by ketalizing 16a -ethylpregnenolone acetate to give 16a -ethyl-3b -acetoxy - pregn - 5 - en - 20 - one 20 - ethyleneketal, hydrolysing this to the 3b -ol and oxidizing this by the Oppenauer method. 16a -Isopropylpregn - 4 - en - 20b - ol - 3 - one 20 - propionate is prepared by esterification of the 20b -ol. |
