| abstract |
A process for preparing very pure ursodeoxycholic acid starting from cholic acid (1) by:n a) selectively oxidising it to 3 alpha, 12 alpha-dihydroxy-7-ketocholanic acid (II) b) reducing acid (II) to 3 alpha, 7 beta, 12 alpha-trihydroxycholanic acid (III) c) oxidising a 3,7-ester of acid (III) to 3 alpha, 7 beta-dihydroxy-12-keto-5-beta-cholanic acid (IV) by treatment with hypochlorite followed by hydrolysisn d) preparing the tris-trimethylsilyl derivative of acid (IV) e) eliminating the trimethylsilyl groups f) reducing the very pure acid (IV) by the Wolff-Kishner method to ursodeoxycholic acid. n Alternatively, the Wolff-Kishner method can be applied directly to the tris-trimethylsilyl derivative, and the trimethylsilyl groups can be eliminated from the final product. |