Use of19F NMR as a direct probe of Δ9desaturase cryptoregiochemistry: a feasibility study

Abstract
19F NMR can be used to monitor the relative efficiency with which various fluorinated aromatic sulfides are oxidized by the Δ9 desaturating system of Saccharomyces cerevisiae. Thus the sulfoxy acids produced from methyl S-(4-(trifluoromethyl)benzyl)-8-mercaptooctanoate (3d), methyl S-(4-(trifluoromethyl)phenyl-2-ethyl))-8-mercaptooctanoate (3e), and methyl S-(4-(trifluoromethyl)benzyl)-9-mercaptononanoate (4c) were observed in the supernatant of S. cerevisiae cultures at concentrations of ~140, ~45, and ~10 μM, respectively. This paper lays the methodological basis for a novel, in vitro "thia test" of cryptoregiochemistry and provides further experimental evidence that the yeast Δ9 desaturase initiates oxidation of stearoyl CoA at C-9. Key words: 19F NMR, desaturase, chiral sulfoxidation, hydrocarbon activation.