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Stereoselective Biocatalytic Synthesis of ( S )‐2‐Hydroxy‐2‐Methylbutyric Acid via Substrate Engineering by Using “Thio‐Disguised” Precursors and Oxynitrilase Catalysis

2007; Wiley; Volume: 13; Issue: 12 Linguagem: Inglês

10.1002/chem.200601114

1521-3765

Martin Fechter, Karl Gruber, Manuela Avi, Wolfgang Skranc, C. Schuster, Peter Pöchlauer, Kurt O. Klepp, Herfried Griengl,

Biofuel production and bioconversion

3-Tetrahydrothiophenone (4) and 4-phenylthiobutan-2-one (7) were used as masked 2-butanone equivalents to give the corresponding cyanohydrins 5 (79 % yield, 91 % ee) and 8 (95 % yield, 96 % ee) in an enzymatic cyanohydrin reaction applying the hydroxynitrile lyase (HNL) from Hevea brasiliensis. After hydrolysis and desulphurisation the desired intermediate (S)-2-hydroxy-2-methylbutyric acid (10) was obtained with 99 % ee. Interestingly, when applying (R)-selective HNL from Prunus amygdalus again the (S)-cyanohydrin 5 was formed (62 % ee). The absolute configuration of 5 was verified by crystal structure determination of the corresponding hydrolysis derived carboxylate. The fact that both enzymes yield the same enantiomer was analysed and interpreted by molecular modelling calculations.