| 摘要 |
<p>Described is a process for the regioselective dehydration of 11-hydroxy steroids using PCl5, PCl3, POCl3 or either SO2Cl2 and imidazole, or PPh3 and CCl4. The disclosed process selectively forms 'DELTA'9,11 steroids from either 11-'alpha'- or 11-'beta'-hydroxy steroids, and can also be used for the one-step conversion of 11,21-dihydroxy steroids to 21-chloro-'DELTA'9,11 steroids. Also disclosed are processes for the regioselective conversion of 11-'beta'-chloro steroids to 'DELTA'9,11 steroids, and for regioselectively converting an 11,17,21-trihydroxy steroid to a 21-chloro-11,17-dihydroxy steroid.</p> |
