Stereospecific ion–molecule reactions of anabolic-type steroid tertiary alcohols with proton-donating cations

Eur. J. Mass Spectrom. 9, 459–464 (2003)
DOI: 10.1255/ejms.578

Stereospecific ion–molecule reactions of anabolic-type steroid tertiary alcohols with proton-donating cations

Vladimir G. Zaikin and Roman S. Borisov
Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninskii pr. 29, 119991 Moscow, Russia. E-mail: zaikin@ips.ac.ru

ABSTRACT:

Isobutane and methane chemical ionization (CI) mass spectra of C-17a-epimeric, 17a-substituted 3-methoxyestra-1,3,5(10),8-tetraen-17a-ols and at C-17- epimeric 17-substituted 3-methoxyestra-1,3,5(10)-trien-17-ols, as well as of some their derivatives, have been studied. In each epimeric pair, the peak intensity ratio [MH–H₂O]⁺ / [MH]⁺ is greater for stereoisomers having an axial (or quasi-axial) hydroxyl group. The same regularity in the peak intensity ratio [MH–CH₃COOH]⁺ / [MH]⁺ is valid for acetates in the D-homo series. The observed quantitative differences in CI mass spectra of epimers are explained by steric hindrance of the attack of the proton-donating cation caused by the angular 18-methyl group. No differences in the ease of elimination of the silanol molecule were observed in CI mass spectra of epimeric silyl ethers.

Keywords: Chemical ionization, gas chromatography/mass spectrometry, isobutane reagent gas, methane reagent gas, 17a-alkyl-17a-hydroxy-D-homoestra-1,3,5(10),8-tetraenes, 17-alkyl-17-hydroxyestra-1,3,5(10)-trienes, stereoisomers, derivatives

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