| 摘要 |
A process for the preparation of a compound of the formula <IMAGE> I wherein R1 is selected from the group consisting of hydrogen, alkyl of 1 to 4 carbon atoms optionally substituted by halogen or a nitrogen or oxygen function and alkenyl and alkynyl of 2 to 4 carbon atoms, R2 is alkyl of 1 to 4 carbon atoms and the A, B, C and D rings are optionally substituted by at least one member of the group consisting of optionally protected -OH or =0, halogen, alkyl and alkoxy of 1 to 4 carbon atoms and alkenyl and alkynyl of 2 to 4 carbon atoms comprising reacting a compound of the formula <IMAGE> II wherein R1 and R2 and the A, B, C and D rings are defined as above with an oxidizing agent in the presence of water and an at least partially water-miscible solvent to obtain a compound of the formula <IMAGE> III wherein R1 and R2 and the A, B, C and D rings are defined as above, subjecting the latter to a solvolysis in a basic or acidic media and optionally subjecting the product to a deprotection reaction of any protected -OH or =0 groups to obtain the compound of formula I and novel intermediates.
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