| The cryptoregiochemistry of the Delta9 desaturase ( S. cerevisiae) was determined using a series of fluorine-tagged thiastearates with the sulfur atom in the 8th, 9th, 10 th or 11th position. Percentage conversion of sulfide to sulfoxide was 1.2%, 7%, 4.5%, 2.0% for the 8-, 9-, 10-, and 11-thia analogues respectively and agreed with previous data using non-fluorinated substrates.;Chemoenzymatic synthesis of fluorine-tagged 12-thia and 13-thiaoleates were investigated in preparation for in vitro sulfoxidation using an over-expressed membrane-bound Delta12 desaturase (desA). Trans-olefin formation was observed for a number of 12 thia substrates including 16F-12S (17%-trans), 18F-12S (22%-trans) and C18-12S (23%-trans) fatty acid methyl esters. The details of a trial in vitro Delta 12 desaturase experiment are reported.;Stereochemical analysis of Delta9 desaturase-mediated sulfoxidation was carried out using methyl 15-fluoro-11-thiapentadecanoate as a test substrate and (S)-(+)-MPAA as the chiral shift reagent. Analysis of (R,S)-methyl 15-fluoro-11-thiapentadecanoate, S-oxide complexed with MPAA in CDC13 revealed doubling of the 19F NMR signal (Deltadelta = 0.01 ppm). Methyl 15-fluoro-11-thiapentadecanoate was oxidized in the yeast whole cell system and the stereochemistry of the predominant enantiomer (S, 32% ee) correlated with the known pro R selectivity of the parent dehydrogenation reaction. |
