Stereoselective substitution of (R)-2-(sulfonyloxy)nitriles with sulfur nucleophiles
摘要:
Optically active 2-(4-toluenesulfonyloxy)- and (4-nitrobenzenesulfonyloxy)nitriles (R)-3 and (R)-4, which were obtained from (R)-cyanohydrins (R)-2 by sulfonylation, react with sulfur nucleophiles such as potassium thioacetate, potassium ethylxanthogenate, potassium thiocyanate, as well as thioalcohols and thiophenol in a typical S(N)2 manner to give the (S)-2-sulfanyl nitriles (S)-7-9 and (S)-11-13 in good chemical yields and enantiomeric excesses. Even (R)-2-methyl-2-(methanesulfonyloxy)hexanenitrile (R)-6, derived from ketone cyanohydrin (R)-5, reacts with potassium thioacetate to yield (S)-2-acetylthio-2-methylhexanenitrile (S)-10 with 97% ee. (C) 1999 Elsevier Science Ltd. All rights reserved.
Synthesis of Aliphatic and α-Halogenated Ketone Cyanohydrins with the Hydroxynitrile Lyase from <i>Manihot esculenta</i>
作者:Johannes Diebler、Jan von Langermann、Annett Mell、Martin Hein、Peter Langer、Udo Kragl
DOI:10.1002/cctc.201300965
日期:2014.4
The potential of the hydroxynitrilelyasefromManihotesculenta towards ketone substrates was investigated. It was observed that the length of the aliphatic chain is a key parameter for the conversion of aliphatic, non‐branched ketones. Smaller substrates are readily converted with high enantioselectivites, but the elongation of the chain length causes a significant loss in enzyme activity. For a
cyclized by LHMDS to give 5,5-disubstituted (S)-4-amino-2(5H)-furanones (S)-4 and (S)-5. Different substituents (H. Me, OBn, OH) in the 3-position of the furanones were introduced by selecting the appropriate acylating agent, which in the case of benzyloxyacetyl chloride led to the novel structure type of 4-amino-3-hydroxyfuranones (S)-5. For the synthesis of 5,5-disubstituted (S)-tetronic acids (S)-8, ketone
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.
(R)-Ketone-cyanohydrins (R)-2 are obtained with high enantioselectivity from aliphatic ketones 1 and HCN in organic solvents using (R)-oxynitrilase (EC 4.1.2.10) as catalyst. Acid catalyzed hydrolysis of the cyanohydrins (R)-2 affords the corresponding (R)-alpha-hydroxy-alpha-methyl-carboxylic acids (R)-3 without measurable racemization.
Synthesis of (R)-cyanohydrins by crude (R)-oxynitrilase-catalyzed reactions in micro-aqueous medium
作者:Shiqing Han、Guoqiang Lin、Zuyi Li
DOI:10.1016/s0957-4166(98)00177-3
日期:1998.6
In diisopropyl ether or ethyl acetate under micro-aqueous conditions, the enantioselective synthesis of (R) cyanohydrins from aldehydes and methyl ketones was studied using crude (R)-oxynitrilase prepared from almonds. This reaction system performed well over the temperature range of 4 degrees C to 30 degrees C. (C) 1998 Elsevier Science Ltd. All rights reserved.