| 摘要 |
<p>Pregn.-4-ene 17alpha, 21-diol 3,20-dione 21-acylates are made by 8a) reaction of pregn-5-ene 3 beta, 17-diol 20 one with 2 mols bromine in organic solvent; (b) reaction of the 5,6,21-tribromo deriv. with a basic alkali metal salt to separate the 5alpha,6beta,dibromo cpd.; (c) treatment with an alkali metal carboxylate and 2 or 3 equivs. alkali metal iodide to form the 21-halo pregnene cpd.; (d) heating with excess carboxylate to complete the 21-carboxylation giving a 21-acylate; (e) treatment with one equiv. bromine to form the 5,6-dibromo cpd.; (f) oxidn. with Jones reagent and cooling; (g) debromination and (h) isomerisation under acid conditions.</p> |
