Electron impact induced fragmentation of steroidal diketones with ‘abnormal’ stereochemistry

The mass spectral fragmentations of steroidal diketones with ‘unnatural’ sterechemistry at positions 8, 9 and 14 have been examined by the use of high resolution, metastable defocusing and isotopic labeling techniques. In addition, the elucidation of fragmentation pathways was greatly facilitated by the use of the INTSUM computer program. In contrast to 14α‐11‐ones, where the McLafferty rearrangement is of minor importance in directing the fragmentation, it is suggested that the ketones in the present study, by virtue of their ring C flexibility, readily undergo the McLafferty rearrangement. If correct, this would represent a further example of available ground state conformations controlling fragmentation after electron impact.