Formation of pentafluorophenyldimethylsilylethers and their use in the gas chromatographic analysis of sterols.

The pentafluorophenyldimethylsilyl group is an excellent protecting group for steroid alcohols, giving volatile ethers, detectable at picogram levels in gas chromatography with an electron capture detector. By the use of five reagents, increasingly hindered hydroxyl groups can be protected, so that structural information about unidentified sterols can be obtained. Quantitative derivative formation for a wide range of hydroxyl groups is possible by selection of the correct reagent combination, without affecting unprotected enolizable ketones.