O. Bortolini, P. Giovannini, Silvia Maietti
2013
Citations
0
Influential Citations
6
Citations
Journal
Journal of Molecular Catalysis B-enzymatic
Abstract
Abstract Both (3 R )- and (3 S )-enantiomers of the chiral green tea flavor compound 3-hydroxy-3-methylnonane-2,4-dione were synthesized by the combined use of acetylacetoin synthase and acetylacetoin reductase from Bacillus licheniformis . The first enzyme was utilized to catalyze the homo-coupling of 2,3-octanedione and obtain the enantioenriched (3 R )-3-hydroxy-3-methylnonane-2,4-dione (ee 44%). The NADH-dependent acetylacetoin reductase was then employed for the diastereoselective (de > 95%) C2 carbonyl reduction of the sole (3 R )-enantiomer of the above 2,4-dione, thus affording the syn diol (2 S ,3 R )-2,3-dihydroxy-3-methylnonan-4-one in enantiomerically pure form. While this step allowed for the recovery of unreacted, optically pure (3 S )-3-hydroxy-3-methylnonae-2,4-dione, the corresponding (3 R )-enantiomer was obtained by subsequent TEMPO-mediated oxidation of the syn diol intermediate. Moreover, using the title compounds as analytical standards, predominance of the (3 R ) enantiomer in the natural flavor compound was finally demonstrated by chiral GC–MS analysis.