Optically active omega-bromocyanohydrins are easily synthesized through an enantioselective (R)-oxynitrilase-catalyzed reaction from their corresponding omega-bromoaldehydes. These cyanohydrins are starting materials for the preparation of medium size nitro gen heterocycles. The reduction of (R)-(+)-5-bromo-2-hydroxypentanenitrile affords, in one-pot, piperidin-3-ol. Azepan-3-ol and azocan-3-ol are readily obtained from their corresponding cyanohydrins in high enantiomeric excesses. (C) 1999 Elsevier Science Ltd. All rights reserved.
Enantioenriched ω-bromocyanohydrin derivatives. Improved selectivity by combination of two chiral catalysts
摘要:
Highly enantioenriched (R)-4-bromo-1-cyanobutyl acetate and (R)-5-bromo-1-cyanopentyl acetate were prepared by acetylcyanation of 4-bromobutanal and 5-bromopentanal, respectively, catalyzed by (S,S)-[(4,6-bis(t-butyl)salen)Ti(mu-O)](2) and triethylamine followed by enzymatic hydrolysis of the minor enantiomer. A cyclic procedure employing the same two chiral catalysts provided inferior results due to a slowly reached steady state and, in reactions with the former substrate, to ring-closure of the free cyanohydrin formed as an intermediate in the reaction. Hydrolysis of the acylated cyanohydrins followed by AgClO4-promoted cyclization provided (R)-2-cyanotetrahydrofuran and (R)-2-cyanotetrahydropyran in essentially enantiopure form. (C) 2012 Elsevier Ltd. All rights reserved.
Optically active (S)-ketone- and (R)-aldehyde-cyanohydrins via an (R)-oxynitrifase-catalysed transcyanation. Chemoenzymatic syntheses of 2-cyanotetrahydrofuran and 2-cyanotetrahydropyran
(R)-Oxynitrilase catalyses the enantioselective decyanation of racemic ketone cyanohydrins and the enantioselective addition of HCN to ω-bromoaldehydes in one step.
Stereocontrolled chemoenzymatic synthesis of 2,3-disubstituted piperidines
作者:Maria I. Monterde、Rosario Brieva、Vicente Gotor
DOI:10.1016/s0957-4166(01)00080-5
日期:2001.3
(R,R)-2,3-Disubstituted piperidines were readily synthesized starting from (R)-(+)- 5-bromo-2-hydroxypentanenitrile (R)-2. An enantioselective (R)-oxynitrilase-catalyzed transcyanation was used to prepare the starting cyanohydrin (R)-2. (C) 2001 Elsevier Science Ltd. All rights reserved.
Enantioenriched ω-bromocyanohydrin derivatives. Improved selectivity by combination of two chiral catalysts
Highly enantioenriched (R)-4-bromo-1-cyanobutyl acetate and (R)-5-bromo-1-cyanopentyl acetate were prepared by acetylcyanation of 4-bromobutanal and 5-bromopentanal, respectively, catalyzed by (S,S)-[(4,6-bis(t-butyl)salen)Ti(mu-O)](2) and triethylamine followed by enzymatic hydrolysis of the minor enantiomer. A cyclic procedure employing the same two chiral catalysts provided inferior results due to a slowly reached steady state and, in reactions with the former substrate, to ring-closure of the free cyanohydrin formed as an intermediate in the reaction. Hydrolysis of the acylated cyanohydrins followed by AgClO4-promoted cyclization provided (R)-2-cyanotetrahydrofuran and (R)-2-cyanotetrahydropyran in essentially enantiopure form. (C) 2012 Elsevier Ltd. All rights reserved.
Chemoenzymatic synthesis of azacycloalkan-3-ols
作者:Maria I Monterde、Serge Nazabadioko、Francisca Rebolledo、Rosario Brieva、Vicente Gotor
DOI:10.1016/s0957-4166(99)00351-1
日期:1999.8
Optically active omega-bromocyanohydrins are easily synthesized through an enantioselective (R)-oxynitrilase-catalyzed reaction from their corresponding omega-bromoaldehydes. These cyanohydrins are starting materials for the preparation of medium size nitro gen heterocycles. The reduction of (R)-(+)-5-bromo-2-hydroxypentanenitrile affords, in one-pot, piperidin-3-ol. Azepan-3-ol and azocan-3-ol are readily obtained from their corresponding cyanohydrins in high enantiomeric excesses. (C) 1999 Elsevier Science Ltd. All rights reserved.