Functionalization of unactivated carbons in 3α,6‐ and 3α,24‐dihydroxy‐5β‐cholane derivatives by dimethyldioxirane

Direct remote functionalization of unactivated carbons by dimethyldioxirane (DMDO) was examined for 3α,6‐ and 3α,24‐dihydroxy‐5β‐cholane derivatives. DMDO oxidation of stereoisomeric methyl 3α,6‐diacetoxy‐5β‐cholanoates caused the direct, unexpected 14α‐ and 17α‐hydroxylations, in analogy with that of the 5α‐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 3α,24‐dihydroxy‐5β‐cholane with DMDO were transformed into the corresponding 5β‐, 14α‐, and 17α‐hydroxy compounds, whereas the ether derivatives yielded the 5β‐hydroxy, 3‐oxo, and C‐24 oxidized products, accompanied by their dehydrated ones.