首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 31 毫秒
1.
《Tetrahedron: Asymmetry》2007,18(13):1529-1532
Enantiomerically pure compounds are important building blocks in the synthesis of natural products. In this study, the reduction of acetophenone to the (S)-isomer of 1-phenylalcohol with a high enantiomeric excess (ee) by locally isolated Alternaria alternata using ram horn peptone (RHP) was investigated. Ten strains of A. alternata were isolated from different plant samples. These isolates were evaluated for the reduction of acetophenone (ACP) to 1-phenylethanol (PEA). Glucose, yeast extract and RHP in a shake flask and fermenter for growth of A. alternata cultures were used. A. alternata EBK-4 isolate was found to be an effective biocatalyst for the enantiomeric bioreduction of acetophenone. Conversions of up to 100% with excellent enantiomeric excesses (>99%) were obtained. Production of PEA was achieved via a fermenter. The yield was calculated as 86%. This is the first report on the enantioselective reduction of ACP by A. alternata using ram horn peptone from waste material.  相似文献   

2.
《Tetrahedron: Asymmetry》2007,18(10):1159-1162
Fourteen strains of Aspergillus niger were isolated from soil samples. These isolates were evaluated for the reduction of acetophenone to 1-phenylethanol. Among the tested isolates, whole cells of the A. niger EBK-9 isolate were found to be an effective biocatalyst for the enantioselective reduction of acetophenone. Under optimized conditions substituted acetophenones were converted to the corresponding optically active alcohol in up to 99% ee.  相似文献   

3.
Immobilized cells of the yeast Cryptococcus laurentii attached to calcium alginate have been introduced as a biocatalyst in the asymmetric reduction of substituted acetophenones. Forty isolates of microorganisms belonging to this taxonomical yeast group were isolated from various samples. Immobilized cells of these isolates were screened as reducing agents for acetophenone 1a to its corresponding alcohol 1b. The four best isolates were selected and identified as Rhodotorula glutinis, Saccharomyces cerevisiae, Hansenula capsulata and C. laurentii by the VITEK 2 compact system. The use of the first three microorganisms is well known and therefore it was decided to explore C. laurentii as a new biocatalyst in organic reactions. The aim was to determine whether C. laurentii could be used to catalyse the bio-reduction of ketones to obtain the (R)- or (S)-isomer of the alcohol with high enantiomeric purity. The isolate C. laurentii EBK-19 was selected for further experiments and studied in detail. More than 70% of the ketones tested were obtained with almost complete conversion (100%), while all the ketones tested were converted to the corresponding (S)-isomer-alcohols in up to >99% enantiomeric excess (ee) under very mild reaction conditions. Amongst the chiral alcohols obtained, the enantiopure 1b obtained from the complete conversion of 1a using C. laurentii EBK-19 was produced on a large scale (9.3 g) using an immobilized cell reaction system. In conclusion, we have presented C. laurentii as a promising biocatalyst for the production of optically active phenylethanols.  相似文献   

4.
《Tetrahedron: Asymmetry》1999,10(5):923-928
The enantioselective reduction of acetophenone was studied in two different ways. Chemical borane reduction using a homogeneously soluble polymer-bound oxazaborolidine catalyst was carried out in a continuously operated membrane reactor and yielded (R)-phenylethanol in good enantiomeric excess with high space–time yields. An enzymatic reduction using a dehydrogenase two-enzyme system as the catalyst and formate as the hydrogen source was carried out in an extractive bi-membrane reactor and yielded (S)-phenylethanol in excellent enantiomeric excess with a low enzyme consumption. A comparison of the two systems with respect to space–time yield, total turnover number and other parameters is made.  相似文献   

5.
A total of 82 fungal isolates were screened for their ability to reduce 3,5-bis(trifluoromethyl)-acetophenone 1. Penicillium expansum was found to successfully reduce ketone 1 in the submerged culture. A second screening was performed on the active P. expansum strains identified by the first screening. A number of strains of P. expansum were found to produce (R)-3,5-bistrifluoromethylphenyl ethanol 2 with over 99% enantiomeric excess (ee) from ketone 1. The most productive strain was identified as P. expansum EBK-9, and this strain was selected for further experiments. The total production of 2 was carried out by P. expansum EBK-9 in a laboratory-scale bioreactor employing optimized conditions as determined by our experiments. P. expansum EBK-9 gave 2 with ee >99% and 76% yield. On a large scale, a total of 3.35 g/L of 2 was produced from 1 after 56 h.  相似文献   

6.
《Tetrahedron: Asymmetry》1998,9(8):1409-1417
Six new sulfur-containing C2-symmetrical bis-β-primary and sec-amino-tert-alcohols have been synthesized from (R)-cysteine and applied successfully in the enantiocontrolled catalytic addition of diethylzinc to benzaldehyde. The resulting 1-phenyl-1-propanol could be obtained in good enantiomeric excess of up to 94%. Using the same chiral auxiliaries in the enantioselective borane reduction of acetophenone afforded 1-phenyl-1-ethanol in enantiomeric excesses of up to 82%.  相似文献   

7.
A novel chiral ionic liquid (CIL) based on nicotinium salt has been synthesized and used as an efficient asymmetric chiral catalyst for reduction of acetophenone derivatives with NaBH4 in methanol at room temperature. The optically active alcohols were obtained in low to moderate enantiomeric excess in a short reaction time.  相似文献   

8.
<正>The enantioselective reduction of acetophenone analogues catalyzed by carrot and celeriac was performed in moderate conversions and excellent enantiomeric excesses.The steric factors and electronic effects of the substituents at the aromatic ring were found to significantly affect the efficiency of the enantioselective reduction of acetophenone analogues,while they had a little effect on the enantioselectivity of acetophenone analogues reduction.It was also found that the conversions of acetophenone analogues reduction at 33℃by means of both biocatalysts were three times as great as those at room temperature.  相似文献   

9.
《Tetrahedron: Asymmetry》2005,16(4):865-868
Some new chiral Schiff bases have been prepared in good yields from various carbonyl groups and two 2-amino alcohols. LiAlH4 was treated with different equivalents of the Schiff bases. Enantioselective reduction of acetophenone is achieved in high chemical yield (up to 93%) with moderate enantiomeric excess (up to 22%) by use of the new reducing agents.  相似文献   

10.
A set of five fungal species, Botrytis cinerea, Trichoderma viride and Eutypa lata, and the endophytic fungi Colletotrichum crassipes and Xylaria sp., was used in screening for microbial biocatalysts to detect monooxygenase and alcohol dehydrogenase activities (for the stereoselective reduction of carbonyl compounds). 4-Ethylcyclohexanone and acetophenone were biotransformed by the fungal set. The main reaction pathways involved reduction and hydroxylations at several positions including tertiary carbons. B. cinerea was very effective in the bioreduction of both substrates leading to the chiral alcohol (S)-1-phenylethanol in up to 90% enantiomeric excess, and the cistrans ratio for 4-ethylcyclohexanol was 0:100. trans-4-Ethyl-1-(1S-hydroxyethyl)cyclohexanol, obtained from biotransformation by means of an acyloin-type reaction, is reported here for the first time. The absolute configurations of the compounds trans-4-ethyl-1-(1S-hydroxyethyl)cyclohexanol and 4-(1S- and 4-(1R-hydroxyethyl)cyclohexanone were determined by NMR analysis of the corresponding Mosher’s esters.  相似文献   

11.
Enantiomerically pure (S)-α-bromohydrins were prepared by the reduction of α-bromoacetophenone analogues catalyzed by an isolated carbonyl reductase from Candida magnolia with high yield and excellent enantiomeric excess when methyl tert-butyl ether was employed as the co-solvent, while avoiding the formation of by-products. This provides a new approach to access these chiral α-bromohydrins which are of pharmaceutical importance.  相似文献   

12.
The biocatalytic reduction of acetophenone derivatives was exploited by using algal biomass from Bostrychia radicans and B. tenella producing exclusively (S)‐2‐phenylethanols with high enantiomeric excess (>99% ee). Bacterial populations associated with algal biomass were identified as the Bacillus genus. This report deals with the first investigations involving the use of marine bacteria associated with B. radicans and B. tenella marine algae for the biocatalytic reduction of acetophenone derivatives.  相似文献   

13.
(S)-1-(2-chlorophenyl)ethanol is a key intermediate of L-cloprenaline used for relieving asthma symptoms. The asymmetric reduction of 2-chloroacetophenone 1 to (S)-1-(2-chlorophenyl)ethanol 2 in the submerged culture of Alternaria alternata isolates was studied. A. alternata EBK-8 isolate was the most effective biocatalyst. The bioactivity of the fungus could be significantly improved by the optimization of culture conditions. Parameters such as pH, temperature, agitation, and incubation time considerably influenced the substrate conversion and the optical purity of the product. The reaction was carried out in a culture medium at a substrate concentration of 30 mmol/L and produced the desired product with high conversion (100%) and isolated yield (80%) with an excellent enantiomeric excess (ee) of >99%. Under the optimum conditions, after 54 h reaction time, 24 mmol/L 2 from 30 mmol/L 1 could be produced. As a result, the submerged fermentation of A. alternata EBK-8 was found to be suitable for the asymmetric reduction of 1 to 2.  相似文献   

14.
Ethyl lactate was used for the first time as a solvent for acetophenone reduction to phenylethanol by borane and sodium tetrahydridoborate. Moderate enantiomeric excess was obtained with the pure reducing agents that could be improved up to 46% by employing stoichiometric amounts of the Lewis acid ZnCl2. These are the highest e.e. values published for solvent‐induced chiral synthesis.  相似文献   

15.
A biocatalytic approach was employed for the asymmetric reduction of sterically demanding ketones to prepare 3-hydroxy-5-oxo-5-phenylpentanoates and 5-hydroxy-3-oxo-5-phenylpentanoates. Screening a collection of microorganisms led to the identification of stereocomplementary microbial strains that provide access to both enantiomers of 3-hydroxy-5-oxo-5-phenylpentanoates and 5-hydroxy-3-oxo-5-phenylpentanoates with high enantiomeric excess (up to 99% ee). Moreover, the application of Saccharomyces cerevisiae gave two diastereomers of 3,5-dihydroxy-5-phenylpentanoates with high enantiomeric excess (up to 99% ee). The applicability of the identified strains was demonstrated by transforming the obtained dihydroxy ester into the chemically valuable lactone (4S,6R)-tetrahydro-4-hydroxy-6-phenyl-pyran-2-one.  相似文献   

16.
A new chiral 1, 3, 2-oxazaborolidine derived from (R)-4-(diphenylhydroxymethyl)-l, 3-thiazolidine has been synthesized and its efficiency in the asymmetric reduction of acetophenone by borane has been investigated. It gives (R)-l-phenylethanol with high enantiomeric excess  相似文献   

17.
The asymmetric reductive coupling reaction of various acrylates derived from D-isosorbide and D-isomannide with acetophenone mediated by samarium diiodide to give both enan-tiomers of the optically active γ-butyrolactone was described.The best enantiomeric excess of the products was 60%.  相似文献   

18.
Four chiral aminodiols from ring opening of (S)-propylene oxide and ethylene oxide wiht n-butylamine and (R) or (S)-α-methylbenzylamine were used to modify LiAlH4. Assymetric reduction of acetophenone and propiophenone gave the highest percent enantiomeric excess when the modifier was made from (S)-oxide and (S)-amine.  相似文献   

19.
Lactic acid methyl ester, lactic acid ethyl ester, and (2S)‐ethyl‐2‐methoxy propanate were used as solvents for acetophenone reduction by boron hydrides. Moderate enantiomeric excess up to 60% was obtained in the presence of stoichiometric amounts of ZnCl2. There is evidence for an intermediate between the solvents, the Lewis acid and the ketone, as the prerequisite for chirality transfer. The importance of the Lewis acid is to strengthen interaction between solvent and educt compared to the hydroxy group.  相似文献   

20.
A series of organochalcogeno acetophenones 3 has been submitted to the action of enzymes from Daucus carota root. Some of the chalcogeno ketones tested afforded the chiral organochalcogeno-α-methylbenzyl alcohols 4 in excellent enantiomeric excesses (>99%), under mild and environmentally friendly conditions. The stereoselectivity of the reduction is in accordance with Prelog’s rule. Enzymatic kinetic resolution as alternative process was used to obtain the chiral ortho-organochalcogeno-α-methylbenzyl alcohols in excellent enantiomeric excess (>99%).  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号