834885-79-9Relevant articles and documents
Hydroxynitrile lyase-catalyzed addition of HCN to 2-substituted cyclopentanones
Kobler, Christoph,Effenberger, Franz
, p. 3731 - 3742 (2007/10/03)
A systematic investigation of the stereoselectivity of hydroxynitrile lyases (HNLs) catalyzed addition of HCN to a variety of monosubstituted cyclopentanones yielding the corresponding cyanohydrins is presented. With PaHNL from bitter almond as catalyst, the HCN addition to 2-alkyl cyclopentanones 1b-d is highly (R)-selective, leading to the cis-(1R,2S)- and trans-(1R,2R)-diastereomers. The addition to the sterically less demanding methyl compound 1a is far less selective. With MeHNL from cassava, the expected (S)-selectivity of the HCN addition is very high for the cyclopentanones 1c-d with larger substituents, but only for the cis-(1S,2R)- and not the trans-(1S,2S)-diastereomers. Dynamic kinetic resolution was observed for the MeHNL-catalyzed addition of HCN to the racemic alkyl 2-oxocyclopentane carboxylates 4a and 4b. Continuous equilibration via keto-enol tautomerism and the preferred enzymatic conversion of the (R)-enantiomers of the ketones 4 results in the formation of the cis-(1R,2S)-diastereomers in >50% yield. The absolute configurations of the synthesized cyanohydrins were determined by X-ray crystallography of O-p-bromobenzoyl derivatives.
