title: 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.
authors: Topchiev Institute of Petrochemical Synthesis, Russian Academy of Sciences, Leninskii pr. 29, 119991 Moscow, Russia. zaikin@ips.ac.ru
authors: Vladimir G
authors: VG
authors: Zaikin
authors: Roman S
authors: RS
authors: Borisov
mesh_terms: D000438:Alcohols / Q000032:analysis / Q000737:chemistry*; D002073:Butanes / Q000737:chemistry; D002412:Cations / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry; D008697:Methane / Q000737:chemistry; D011522:Protons; D013237:Stereoisomerism; D013256:Steroids / Q000032:analysis / Q000737:chemistry*
chemical_list: D000438:Alcohols; D002073:Butanes; D002412:Cations; D011522:Protons; D013256:Steroids; D008697:Methane