Translational energy release and stereochemistry of steroids. IX-The mechanism of the elimination of water from metastable ions in epimeric 3-hydroxy steroids of the 5β-series

Autor: Z. V. I. Zaretskii, J. H. Beynon, Carl Djerassi, J. M. Curtis, A.G. Brenton
Rok vydání: 1988
Předmět:
Zdroj: Organic Mass Spectrometry. 23:460-468
ISSN: 1096-9888
0030-493X
DOI: 10.1002/oms.1210230606
Popis: The mechanism of water elimination from metastable molecular and [M − CH3˙]+ ions, as well as from ions deprived of ring D, in epimeric 3-hydroxy steroids of the 5β-series has been elucidated by deuterium labelling, by the measurements of the translational energy released during loss of water, and by collision-induced decomposition mass-analysed ion kinetic energy spectrometry. It was found that the dehydration of the metastable molecular ion in 3α-hydroxy steroids of the 5β-series occurs mostly regiospecifically as an elimination of the 3α-hydroxyl together with the 9α-hydrogen atom. The ring A in the molecular ion has to flip to the boat conformation to make this reaction possible. In the metastable molecular ion of 3β-hydroxy steroids of the 5β-series a different dehydration mechanism operates, with very little participation of the 9α-hydrogen atom. The mechanisms of water loss from metastable [M − CH3˙]+ ions and from ions deprived of ring D differ from that of the molecular ion.
Databáze: OpenAIRE
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