Splitting off of water from the molecular ions of steroidal cyclopropyl ketones

Abstract

Mass spectra of 14 steroids containing a cyclopropane ring in the vicinity of a keto group were measured and the signals of the ions [M-H2O]+, [M-CH3]+ and [M-CO]+ were sought. Using models labelled selectively with deuterium it was shown that the water molecule, split off from the molecular ion of 3α,5-cyclo-5α-cholestan-6-one (I) is formed from the hydrogen atoms located in the positions 2β and 9α.