| 摘要 |
The invention comprises 21-bromo-pregna-3, 11, 20-triones having the formula: <FORM:0965572/C1/1> in which R1 and R2, and R3 and R4 each form a double bond between the 4(5) and the 16(17) positions respectively or R1 is a bromine atom, R3 is an a -bromine atom, and R2 and R4 are hydrogen atoms and processes for the preparation thereof by oxidising and brominating 3a -hydroxy-17a , 21-dibromo-pregnane-11, 20-dione to form 4, 17a , 21-tribromo-pregnane-3, 11, 20-trione and eliminating hydrogen bromide therefrom to obtain 21-bromo-pregna-4, 16-dien-3, 11, 20-trione. Oxidation and bromination may be effected with N-bromo-succinimide and elimination of hydrogen bromide with lithium halide-lithium carbonate couple in dimethyl formamide. |
