标题：Stereospecific Dehydrogenation of (25R)-and (25S)-3α, 7α, 12α-Trihydroxy-5β-cholestanoic Acids by Acyl-CoA Oxidase in Rat Liver Light Mitochondrial Fraction
摘要：From a stereochemical point of view, the dehydrogenation mechanism of the biotransformation of 3α, 7α, 12α-trihydroxy-5β-cholestanoic acid (THCA) into (24E)-3α, 7α, 12α-trihydroxy-5β-cholest-24-enoic acid (Δ24-THCA) has been studied with capillary gas chromatography (GC)/negative ion chemical ionization (NICI)-mass spectrometry. After incubation of (24R, 25R)-or (24S, 25S)-[24, 25-2H2] THCA, synthesized from (24E)-Δ24-THCA by a deuterated diimide reduction, with a rat liver light mitochondrial fraction, 5β-cholestanoic acids were extracted and derivatized into a pentafluorobenzyl (PFB) ester-dimethylethylsilyl (DMES) ether. Subsequent resolution into THCA and Δ24-THCA was attained by GC on a cross-linked 5% phenylmethyl silicone fused-silica capillary column monitored with a corresponding characteristic carboxylate anion [M-PFB]- in the NICI mode. The stereospecific elimination of a pro-R hydrogen at C-24 in both (25R)-and (25S)-THCA indicated syn-elimination for the former, whereas anti-elimination for the latter was observed.
