Stereospecific Ion—Molecule Reactions of Anabolic-Type Steroid Tertiary Alcohols with Proton-Donating Cations

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-H(2)O](+) / [MH](+) is greater for stereoisomers having an axial (or quasi-axial) hydroxyl group. The same regularity in the peak intensity ratio [MH-CH(3)COOH](+) / [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.

Mass Spectrometry in Russia

“…66 For example, the pronounced stereospecificity of ion-molecule reactions with proton-donating gas-reagents has been observed in the series of 17-and 17a-epimeric 17a-alkyl-17a-hydroxy-d-homo-estra-1,3,5(10),8-tetraenes, 17-alkyl-17-hydroxy-estra-1,3,5(10)-trienes and their acetates. 67 The observed quantitative differences between CI mass spectra of stereoisomers were explained by steric hindrance for the attack of proton-donating cations. Similar "approach control" was suggested to explain the stereospecificity of the protonation of tertiary alcohols in the transdecahydro-4-hydroxyquionoline series.…”

Recent Developments in the Isolation and Synthesis of D‐Homosteroids and Related Compounds

“…65 The results of CI-MS investigations on 17-substituted estra-and 17a-substituted-D-homoestra-derivatives have been reported. 66 Computational studies have shown that derivatives of tetrahydrochrisene (82) can be successfully docked into the second binding site of ERα and ERβ (Figure 8). …”