Epimeric 3a a,7a a,16-and 3a a,7a a,15-trihydroxy-5b b-cholan-24-oic acids and some related compounds were synthesized from chenodeoxycholic acid (CDCA) and ursodeoxycholic acid (UDCA), respectively. The key reaction involved one-step remote oxyfunctionalization of unactivated methine carbons at C-17 of CDCA and at C-14 of UDCA as their methyl ester-peracetate derivatives with dimethyldioxirane (DMDO). After dehydration of the resulting 17a a-and 14a a-hydroxy derivatives with POCl 3 or conc. H 2 SO 4 , the respective D D 16 -and D D 14 -unsaturated products were subjected to hydration via hydroboration followed by oxidation to yield the 3,7,16-and 3,7,15-triketones, respectively. Stereoselective reduction of the respective triketones with tert-butylamine-borane complex afforded the epimeric 3a a,7a a,16-or 3a a,7a a,15-trihydroxy derivatives exclusively. A facile formation of the corresponding e e-lactones between the side chain carboxyl group at C-24 and the 16a a-(or 16b b-) hydroxyl group in bile acids is also clarified.
A Highly Efficient, Stereoselective Oxyfunctionalization of Unactivated Carbons in Steroids with Dimethyldioxirane.-A variety of steroids such as (I) and (V) are transformed in a stereoselective one-step remote oxidation to novel mono-and dihydroxylated compounds. -(IIDA,
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