Equatorial secondary alcohol functionality

One recognizes an oxane ring (tetrahydropyran) substituted by three secondary alcohol functions in an equatorial orientation, a side chain carrying a primary alcohol function and finally a hemiacetal hydroxyl carried by carbon 1. This intramolecular hemiacetal is derived from the addition of the oxygen carried by C-5 to an aldehyde function. 

Enzymatic acyl transfer reactions are also practical processes for the acylation of hydroxyl groups in steroids [25]. The lipase from Chromobacterium viscosum (CVL), for instance, selectively transfers butyric acid from trifluoroethyl butyrate to equatorial 3p-alcoholic functions being present in a variety of sterols, such as 107, 110, and 113 (Table 9). Axially oriented alcohols at C-3 and secondary alcohols at C-17 (107 and 110) or in the sterol side chains (113) are not derivatized. In addition to the equatorial alcohols, the... 

The reactivity of various steroid alcohols decreases in the order primary > secondary (equatorial) > secondary (axial) > tertiary. The only systematic investigation relating to the selective protection of steroidal hydroxyl functions has been carried out with the cathylate (ethyl carbonate) group. Since only equatorial hydroxyl groups form cathylates this ester has been used as a diagnostic tool to elucidate the configuration of secondary alcohols. 

Ruthenium catalyzed oxidation of alcohols. Primary and secondary alcohols are oxidized by this amine oxide in the presence of various ruthenium compounds. This particular amine oxide is superior to a number of others. Acetone, DMF, and HMPT are the most satisfactory solvents. Only ruthenium compounds can function as catalysts. RuCla is the cheapest catalyst, but is poorly soluble in acetone. RuCl52[P(CeH5)3] and Ru3(CO)ia do not suffer from this limitation. Saturated primary and secondary alcohols are oxidized in high yield allylic alcohols are generally oxidized in satisfactory yields, but homoallylic alcohols arc inactive and tend to give low conversions. Cholesterol is not oxidized. There is little discrimination between axial and equatorial hydroxyl groups. ... 

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