Mass spectra of bile acid methyl ester acetate derivatives

Abstract

AbstractDeuterium labeling in the acetate derivatives of cholic acid demonstrates that electron impact induced consecutive loss of HOAc from the molecular ion occurs in the following order of decreasing preference: 12α‐OAc > 7α‐OAc > 3α‐OAc. Numerous examples are presented showing that consecutive loss of HOAc from a common ion generally increases progressively with relative intensity. In the acetate pregnan‐20‐one derivatives of cholic acid, loss of 43 mass units from the molecular ion comes from the 12α‐OAc and not the 17β‐acetyl sidechain. Ketene is ejected from an acetoxy group located in an α position to a carbonyl on which an ion‐radical charge is localized.