Abstract
Using Methyl 2, 4-Dibromo-3, 12-dioxocholanate (III) as a starting material Methyl 3, 12-dioxochola-1, 4-dienate (IV) and methyl 3, 12-dioxochola-4, 6-dienate (VI) were prepared. Methyl 3, 12-dioxochola-1, 4, 9 (11)-trienate (IX) was obtained by bromination and dehydrobromination of methyl 3, 12-dioxocholanate (II) or dehydrogenation with selenium dioxide in tert-amyl alcohol of methyl 3, 12-dioxochol-9 (11)-enate (VIII). Aromatization of IX with zinc in pyridine, dimethylformamide, or ethanol afforded 3-hydroxy-12-oxo-19-norchola-1, 3, 5 (10), 9 (11)-tetraenic acid methyl ester (X). Hydrogenation, followed by chromium-trioxide-oxidation and Huang-Minlon reduction or Huang-Minlon reduction and then hydrogenation of X afforded 3-hydroxy-19-norchola-1, 3, 5 (10)-trienic acid methyl ester (XVIII).
