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.
Dramatic alteration of sphingolipid bases of Hansenula ciferrii by exogenous fatty acid.
Abstract Hansenula ciferrii , a yeast which normally excretes large amounts of C18-phytosphingosine in the form of its tetra-acetyl derivative, was grown in basal medium containing added pentadecanoic acid (0.1%) and Brij 58 (1%). Analyses of the sphingolipid bases recovered from the culture medium indicated the presence of significant quantities of C17-phytosphingosine (39%) and C19-phytosphingosine (15%) in addition to the normal C18-phytosphingosine (46%). The sphingolipid bases were characterized by gas-liquid chromatography combined gasliquid chromatography-mass spectrometry, and chemical degradation.
Über Steroide und Sexualhormone. 156. Mitteilung. Über die reduktive Aufspaltung von Steroid-epoxyden mit Lithiumaluminiumhydrid, I. Synthese von 3β,5-Dioxy-koprostan
Lithiumaluminiumhydrid eignet sich gut zur reduktiven Aufspaltung bestimmter Steroid-epoxyde. In den untersuchten Fallen verlief die Hydrierung sterisch einheitlich und eroffnete damit erstmals einen praparativ gunstigen Weg zur Bereitung von Derivaten des 5-Oxy-koprostans.