MASS SPECTROMETRY IN STRUCTURAL AND STEREOCHEMICAL PROBLEMS .176. COURSE OF ELECTRON IMPACT INDUCED FRAGMENTATION OF ANDROSTANE

The fragmentation of the androstane skeleton differs drastically from that of C-17-substituted steroidal hydrocarbons such as cholestane or pregnane. The characteristic ring D fragmentation of the latter leading to peaks at m/e 217 and 218 is relatively unimportant in the absence of a C-17 substituent. Instead, androstane suffers appreciable fragmentation in ring A and through extensive deuterium labeling, the nature of this fragmentation– notably the course of a reciprocal hydrogen transfer–has been elucidated. Another striking difference between the mass spectrum of androstane and 17β-ethylandrostane (pregnane) is the origin of the expelled methyl radical associated with the characteristic M – 15 peak. Mechanistic rationalizations for the various fragmentation processes are presented as are synthetic details for the preparation of the various deuterated analogs. © 1969, American Chemical Society. All rights reserved.