Mass spectrometry of sterols. Electron ionization induced fragmentation of C-4-alkylated cholesterols

The electron impact ionization of C-4-alkylated cholest-5-en-3beta-hydroxysterols has been investigated. The mass spectra of the C-4-alkylated cholesterols contain a number of ions in the high mass region for which analogous ions are not found in the spectrum of cholesterol. Detailed studies of the composition and origin of these ions have been made by high resolution mass spectrometry and analysis of metastable ions. In addition, a large number of isotopically (deuterium and 18O) substituted C-4-alkylated analogues have been prepared to assist in the interpretation of the spectra. The combined results indicate the occurrence of a number of very complex and unusual electron ionization induced fragmentations. Most notable of the findings reported herein concerns the demonstration of the formation of an ion involving loss of the elements of ring A with an intramolecular shift of the oxygen and hydrogen atoms of the hydroxyl function to the charge-retaining species.

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.

Chemical synthesis, spectral properties, and chromatography of 4alpha-methyl and 4beta-methyl isomers of (24R)-24-ethyl-5alpha-cholestan-3beta-ol and (24S)-24-ethyl-cholesta-5,22-dien-3beta-ol

Described herein are chemical syntheses of the following compounds: 4-methyl-(24S)-24-ethyl-cholesta-4,22-dien-3-one, 4,4-dimethyl-(24S)-24-ethyl-cholesta-5,22-dien-3-one, 4beta-methyl-(24R)-24-ethyl-5alpha-cholestan-3beta-ol, 4alpha-methyl-(24R)-24-ethyl-5alpha-cholestan-3beta-ol, 4alpha-methyl-(24S)-24-ethyl-5alpha-cholest-22-en-3beta-ol, 4-methyl-6beta-bromo-(24S)-24-ethyl-cholesta-4,22-dien-3-one, 4alpha-methyl-(24S)-24-ethyl-cholesta-5,22-dien-3beta-ol, 4alpha,5alpha-epoxy-(24S)-24-ethyl-cholesta-4,22-dien-3beta-yl acetate, 4beta-methyl-(24S)-24-ethyl-cholest-22-en-3beta,5alpha-diol, 4beta-methyl-5alpha-hydroxy-(24S)-24-ethyl-cholest-22-en-3beta-yl acetate, 4beta-methyl-(24S)-24-ethyl-cholesta-5,22-dien-3beta-yl acetate and 4beta-methyl-(24S)-24-ethyl-cholesta-5,22-dien-3beta-ol. Chromatographic, nuclear magnetic resonance, and mass spectral data are presented for the compounds under consideration.