Mass spectra of 18α,19βH-ursane derivatives with a lactone arrangement of the ring E

Abstract

The character of the mass spectra of a series of 25 18α,19βH-ursane derivatives with a six-membered or five-membered lactone bridge in the ring E does not depend, surprisingly, on the substitution in the ring E. In all instances of 3β-acetoxy- and 3β-hydroxy derivatives the dominant ions of the spectrum are formed by the loss of the methyl radical and the ethylene molecule, while the lactone ring and further oxygen-containing functions in the ring E are not fragmented.