Diethylhydrogensilyl cyclic diethylsilylene derivatives in gas chromatography/mass spectrometry of hydroxylated steroids. III-Fragmentations of 5β-pregnane-17,20,21-triol derivatives
AbstractA reaction of N,O‐bis‐(diethylhydrogensilyl) trifluoroacetamide with 5β‐pregnane‐17,20,21‐triols afforded diethylhydrogensilyl (DEHS) cyclic diethylsilylene (DES) derivatives. 5β‐Pregnane‐3α,17α,20β,21‐tetraol yielded the 3α,21‐bis‐DEHS‐17α,20β‐DES compound, whereas the structure of the major product from its 20α isomer was assigned as the 3α,17α‐bis‐DEHS‐20α,21‐DES derivative, which would undergo facile isomerization to the unstable 3α,21‐bis‐DEHS‐17α,20α‐DES structure under electron ionization. Fragmentations of these DEHS‐DES compounds are discussed on the basis of isotope labelling experiments, linked scanning data, and accurate mass measurements.