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Functionalization of unactivated carbons in 3alpha,6- and 3alpha,24-dihydroxy-5beta-cholane derivatives by
Takashi Iida1, Keisuke Shiraishi, Shoujiro Ogawa
1Department of Chemistry, College of Humanities & Sciences, Nihon University, Setagaya, Sakura-jousui, Tokyo 329-1151, Japan, takaiida@chs.nihon-u.ac.jp
Abstract:
Direct remote functionalization of unactivated carbons by dimethyldioxirane (DMDO) was examined for 3alpha,6- and 3alpha,24-dihydroxy-5beta-cholane derivatives. DMDO oxidation of stereoisomeric methyl 3alpha,6-diacetoxy-5beta-cholanoates caused the direct, unexpected 14alpha- and 17alpha-hydroxylations, in analogy with that of the 5alpha-H analogs, regardless of the differences in stereochemical configuration of the A/B-ring junction and of the acetoxyl groups at C-3 and C-6. On the other hand, the ester derivatives of 3alpha,24-dihydroxy-5beta-cholane with DMDO were transformed into the corresponding 5beta-, 14alpha-, and 17alpha-hydroxy compounds, whereas the ether derivatives yielded the 5beta-hydroxy, 3-oxo, and C-24 oxidized products, accompanied by their dehydrated ones.