Hydroxylation of Deuterated 1,4-Cineoles by Bacillus cereus

Article abstract of DOI:10.1021/jo00075a028

The stereochemistry and mechanism of 1,4-cineole hydroxylation by the cytochrome P-450-containing strain of Bacillus cereus UI-1477 was examined using specifically deuterated substrates.Stereospecifically deuterated 1,4-cineoles were synthesized by Wolff-Kishner reductions of enantiomeric 2-oxo-1,4-cineoles, and by Barton-McCombie elimination of the alcohol functional group of 2-hydroxy-2-deutero-(1R,4S)-cineole.Products obtained from hydroxylations of 2-deutero-(1R,4S)-cineole and enentiomeric 2,2,3,3-tetradeutero- and 2,2,3-trideutero-1,4-cineoles were isolated and characterized by gas chromatography/mass spectrometry and by 1H- and 2H-NMR spectroscopy.Deuterium at the site which is oxygenated does not change hydroxylation stereospecificity, but it dramatically shifts the relative ratios of 2-endo- and 2-exo-alcohol products formed.Analysis of cineole alcohols obtained by microbial hydroxylation of multiply-deuterated-1,4-cineoles indicated that the starting materials contained deuterium at both the 2- and 6-positions, suggesting that a 2,6-proton migration occurs during the Wolff-Kishner reduction of enantiomerically pure 2-oxo-1,4-cineoles.Ratios of cineole alcohols formed from monodeuterated-1,4-cineoles reveal the likehood of a two-step machanism involving nonspecific hydrogen atom removal followed by stereospecific hydroxylation.