Preparation of optically active cyanohydrins using the (S)-hydroxynitrile lyase from Hevea brasiliensis

‘Gelozymes’ in organic synthesis. (Part 3): Lipase mediated synthesis of enantiomerically pure (R)- and (S)-enantiomers of 2-acetoxy-4-phenyl-(E)-but-3-enenitrile

“…From the known stereochemical preference of P. cepacia lipase for (S)-cyanohydrin esters, the unreacted acetate should have (R)-configuration and the cyanohydrin produced should have (S)-configuration. The formation of (S)-cyanohydrin 5 by stereospecific addition of HCN to cinnamaldehyde catalyzed by oxynitrilase from Hevea brasiliensis with 95% ee has been reported by Griengl et al 21 The reported ½a 25 D is )27.9 (c 1.95, CHCl 3 ) while the (R)-acetate obtained during our experiments with P. cepacia lipase has ½a 25 D of )22 (c 2.0, CHCl 3 ). Since oxynitrilase from Hevea brasiliensis was not readily available, we prepared the (R)-cyanohydrin using (R)-oxynitrilase from almonds (Prunus amygdalis) as described by Han et al 22 in 50% ee.…”

Immobilized Hydroxynitrile Lyases for Enantioselective Synthesis of Cyanohydrins: Sol‐Gels and Cross‐Linked Enzyme Aggregates

“…The results obtained suggest that the substrate/ product deactivation phenomenon is significant for PaHNL and MeHNL whereas free HbHNL remained active over the course of the reaction (3 days). Furthermore, conversion ratios reported by Griengl et al for this substrate in biphasic [29] and aqueous [30] media by HbHNL were significantly different (95 % and 55 %, respectively). This trend seems to indicate that greater concentrations of 2b in the aqueous phase deactivate HbHNL.…”

Uneven twins: Comparison of two enantiocomplementary hydroxynitrile lyases with α/β-hydrolase fold

“…Beside the substrate range of the synthesis reaction, which was extensively described for PaHNL (Dreveny et al, 2002;Weis et al, 2004) as well as for all three ␣/␤-hydrolase enzymes (Schmidt et al, 1996;Andexer et al, 2007;Förster et al, 1996), a detailed knowledge about the catalysts' stability and inactivating parameters is important. Such data are a prerequisite to design optimal reaction conditions for technical applications or to overcome limitations by mutagenesis, as was demonstrated for the most widely used HNLs from P. amygdalus and H. brasiliensis (Hickel et al, 1997;Glieder et al, 2003).…”