Mass spectral fragmentation of 5alpha-hydroxysteroids.

The mass spectra of a number of C-4alpha- and C-4beta-alkylated cholestan-3beta, 5alpha-diols have been found to contain an intense ion at m/e 332. the corresponding 6beta-alkylated (R) cholestan-3beta, 5alpha-diols exhibit an abundant ion at m/e 331 + R. The mass spectra of cholestan-5alpha-ol and cholestan-3beta, 5alpha-diol also show an ion at m/e 332 which, however, is of relatively low abundance. The ion in question appears to arise from fragmentation processes which are characteristics of 5alpha-hydroxysteroids. A similar fragmentation has been found to occur in cases of C-4 and C-6beta-alkylated 5alpha-hysroxy-cholestan-3-ones. The results of isotopic labeling, high resolution and metastable ion defocusing studies are discussed in terms of the origin of several of the ions in the spectra of the various compounds.