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1.
Robert Chênevert Daniel Goupil Yannick Stéphane Rose Emmanuelle Bédard 《Tetrahedron: Asymmetry》1998,9(24):4950-4288
The stereoselective acylation of meso-tetrahydropyrans 6 and 7 by enol esters (vinyl acetate or isopropenyl acetate) in the presence of Candida antarctica lipase in organic media gave the corresponding (2R,4S,6S)-monoesters 10 and 11 in high enantiomeric purity. The hydrolysis of the corresponding diacetate derivatives 8 and 9 in the presence of the same enzyme provided the opposite enantiomers, (2S,4R,6R)-monoesters 10 and 11. 相似文献
2.
Nicola DAntona Daniela Lambusta Raffaele Morrone Giovanni Nicolosi Francesco Secundo 《Tetrahedron: Asymmetry》2004,15(24):3835-3840
Lipase from Candida antarctica has been successfully used to realise the selective esterification of the four 1-(1-hydroxyethyl)-3-ethylferrocene isomers, possessing central/planar chirality. In this reaction, the lipase recognises only the two isomers possessing an (R)-configuration, independently from planar chirality. This allows us to split the mixture into two couples of diastereoisomers, namely the (Sp,Rc)-/(Rp,Rc)- and (Rp,Sc)-/(Sp,Sc)-isomers, conveniently separated in the single constituents by crystallisation from hexane. 相似文献
3.
Gun Hedström Sune Backlund Folke Eriksson Stefan Karlsson 《Colloids and surfaces. B, Biointerfaces》1998,10(6):113-384
A hydrogel stable in an organic solvent has been developed. This pseudo-solid aqueous gel (PAG) consists of only native gelatin and water, and has been used for immobilization of enzymes. A relatively high amount of gelatin is required in order to obtain stable gels. PAGs containing the enzyme Candida antarctica lipase (SP 525) were successfully used in catalysing the esterification of R/S-(±)-2-octanol and hexanoic acid in hexane. The conversions as well as the enantiomeric excess values of the product, R-(−)-2-octyl hexanoate, were high and comparable to those obtained with microemulsion-based gels. The PAGs containing immobilized lipase gave reproducible results and may be re-used several times. The gels are easy to prepare and use, non-toxic and biocompatible. The PAGs retain their integrity in organic solvents and may be used in preparative-scale synthesis of organic compounds. 相似文献
4.
Amparo Luna Covadonga Astorga Ferenc Fülöp Vicente Gotor 《Tetrahedron: Asymmetry》1998,9(24):1916-4487
(±)-cis-N-Benzyloxycarbonyl-2-aminocyclopentanol was efficiently resolved by O-acylation with Pseudomonas cepacia lipase, as was (±)-cis-N-benzyloxycarbonyl-2-aminocyclohexanol when Candida antarctica lipase was used. 相似文献
5.
Chiral tertiary alcohols and their esters represent important flavor compounds and are useful building blocks. Unfortunately, they are accepted by only a few lipases/esterases as substrates and enantioselectivity is usually very low. We report here a highly enantioselective transesterification of the tertiary alcohol 2-phenylbut-3-yn-2-ol using lipase A from Candida antarctica (CAL-A). Under optimized conditions, the corresponding acetate was obtained with 94%ee at 35% conversion equivalent to an enantioselectivity factor of E=65. In contrast, enantioselective hydrolysis of the racemic acetate was not feasible as this is very prone to autohydrolysis. 相似文献
6.
I. Hilker A.E.J. Schaafsma R.A.H. Peters A. Heise A.J. Nijenhuis 《European Polymer Journal》2008,44(5):1441-1450
A detailed study of a mild lipase-catalyzed route to cyclic ester oligomers based on diester and diol monomers is provided. A systematic variation of acyl donor and acceptor substrates enabled us to relate cyclization to their structural elements and elucidate the role of the immobilized Candida antarctica lipase B (Novozym 435) in this process. Moreover, its potential for optimization and as a tool for the production of cyclic oligoesters as monomers was investigated. For instance, a series of cyclic oligoesters of di-, tri-, tetra- and pentaethylene terephthalate was obtained in excellent purities (>99%) and conversions. Furthermore, 2,5- and 2,6-pyridinodicarboxylate combined with diethylene glycol yielded high amounts of cyclic oligoesters. Also cyclic oligoesters of propylene terephthalate were produced in good purity (84%) in toluene at moderate temperature (70 °C at 285 mbar). In some cases the cyclic dimer with rotational C2 symmetry was preferentially obtained. 相似文献
7.
Ahmed Kamal Mahendra Sandbhor Kaleem Ahmed S. F. Adil Ahmad Ali Shaik 《Tetrahedron: Asymmetry》2003,14(24):3861-3866
A new practical method for the enzymatic synthesis of 1,2-diols has been developed by employing a lipase catalyzed one-pot transesterification protocol. A series of substituted -acetoxyphenylethanones 3a–g have been reduced to the corresponding alcohols under mild conditions employing sodium borohydride and moist neutral alumina, and further subjected for lipase catalyzed irreversible transesterification in the same pot to give mono- and diacetate diols (R)-4 and (S)-5, which on hydrolysis afforded terminal 1,2-diols, (R)- and (S)-6 in high enantiomeric excess. 相似文献
8.
Carlos E. Costa Giuliano C. Clososki Henrique B. Barchesi Sandra P. Zanotto M. Graa Nascimento Joo V. Comasseto 《Tetrahedron: Asymmetry》2004,15(24):2043-3954
Kinetic resolutions of a number of β-hydroxy selenides promoted by enzymes were performed using PPL (free Porcine pancreatic lipase), PSL (Amano PS—free Pseudomonas sp. lipase) and CALB (NOVOZYM 435®—immobilized Candida Antarctica lipase type B) with (RS)-1-phenylselanyl-propan-2-ol. CALB gave the best results and provided both (R)- and (S)-enantiomers in high enantiomeric purity. A comparative study of the effect of temperature, solvent, enzyme immobilization and the structure of the substrates on the resolution is presented. 相似文献
9.
Esterification of mandelic acid catalysed by Candida antarctica lipase B was studied by Fourier transform (FT) Raman spectrometry in non-aqueous medium. It was found that there is a strict correlation between the intensity of the Raman scattering and the activity of the enzyme. FT-Raman spectrometry seems to be a fast and reliable method for selecting the appropriate enzyme and for determining the optimal enzyme water content. In addition, valuable information can be obtained from the spectra regarding the mechanism of enzyme–substrate bonding. 相似文献
10.
The reaction of various chiral 2,2′-diaryldialdehydes with achiral and chiral 1,2-diamines in the presence of Lewis acids to give imidazo[1,2-a]azepines was investigated. Best results were achieved with Yb(OTf)3; the reaction outcome is strongly dependent upon the geometric features of both reactants. Kinetic resolution of rac-2,2′-dinaphthyldialdehyde with (R,R)-1,2-diphenyl-1,2-diamminoethane (up to 92% e.e.) was achieved. 相似文献
11.
Pierre Duhamel Philippe Renouf Dominique Cahard Albert Yebga Jean-Marie Poirier 《Tetrahedron: Asymmetry》1993,4(12):2447-2450
Enzymatic hydrolysis of prochiral dienol diacetate 1 by Candida cylindracea lipase (C C L) leads to the keto enol acetate 2 in high yield with an enantiomeric excess> 98 %. The S configuration of the asymmetric center was assigned. 相似文献
12.
Yutaka Aoyagi Naoki Agata Noriko Shibata Mai Horiguchi Robert M. Williams 《Tetrahedron letters》2000,41(52):4221-10162
The lipase TL®-mediated kinetic resolution of (±)-benzoin (1) proceeded to give the corresponding optically pure benzoin (R)-1. On the other hand, (S)-benzoin-O-acetate (5) could be hydrolyzed without epimerization to give (S)-benzoin (S)-1, under alkaline conditions. Further, (R)-1 was converted to (1R,2S)-2-amino-1,2-diphenylethanol (99:1 er) according to the procedure reported previously. 相似文献
13.
Christian Orrenius Torbj rn Norin Karl Hult Giacomo Carrea 《Tetrahedron: Asymmetry》1995,6(12):3023-3030
For further investigation of the kinetic resolutions in transesterification reactions with the highly enantioselective Candida antarctica lipase B, an easy to study model reaction with one typical substrate, the Douglas Fir Beetle pheromone 3-methyl-2-cyclohexen-1-ol (Seudenol), was developed. The influence of the nature of the solvent and thermodynamic water activity was studied. Initial rates showed constant or progressively increasing values with increasing water activity. Enantioselectivity depended on the choice of solvent and descended in most cases with increasing water activity. No general correlations of enantioselectivity or activity with physicochemical constants of the solvent were found. However, at a water activity of 0.11 a tendency toward optimum hydrophobicity (i.elog P ≈ for enantioselectivity was observed. Enantiomeric ratios were in the range 8–32. 相似文献
14.
Based on the lipase-catalysed kinetic resolution of the silyloxyalcohol (1RS,2SR)-5 by transesterification with vinyl acetate in the presence of lipase from Pseudomonas cepacia a synthesis of both enantiomers of the β-amino acid cispentacin (1R,2S)-1 and (1S,2R)-1 using simple functional group interconversions is described. 相似文献
15.
A method for the regio- and enantioselective protection and deprotection of a number of cyclobutanone derivatives employing the isolated enzyme porcine pancreatic lipase (PPL) has been developed. PPL catalyzes the regioselective acylation or deacylation of the C-3 substituent in (2S,3R)-(+)-bis[hydroxymethyl]-1,1-dimethoxycyclobutanone and its enantiomer. Photochemical ring expansion of the corresponding cyclobutanones in methanol gave anomeric mixtures of the methyl furanosides with stereochemical retention of the ring substituents. The PPL-catalyzed hydrolysis of the acetal derived from (2S,3R)-bis[acetoxymethyl]cyclobutanone resulted in a regioselective reaction of the C-3 acetoxymethyl group. PPL exhibits no hydrolysis activity toward the acetal derived from the enantiomeric cyclobutanone diacetate.
Racemic 2-acetoxymethyl-3,3-dimethylcyclobutanone was converted to its enantiomerically enriched (S)-alcohol by PPL-catalyzed hydrolysis. The corresponding methyl furanoside obtained from the photochemical ring expansion of racemic 2-acetoxymethyl-3,3-dimethylcyclobutanone in methanol is not an effective substrate for PPL mediated hydrolysis. 相似文献
16.
Mariappan Periasamy Muthu Seenivasaperumal Vutukuri Dharma Rao 《Tetrahedron: Asymmetry》2004,15(24):3847-3852
Methods of synthesis of new chiral amino ether derivatives through the opening of aziridinium ions, prepared in situ using trans-(±)-2-(1-N,N-dialkylamino)cyclohexyl mesylate with (R)-(+)-1,1′-bi-2-naphthol, are described. The (R,R,R)-diastereomer was obtained as the major product and isolated as an enantiopure salt, and characterized by single crystal X-ray analysis. The C2-chiral (R,R,R,R,R)-diamino ether was obtained as the major product by opening of the aziridinium ion, prepared using trans-(±)-2-(1-pyrrolidino)cyclohexyl mesylate and (R)-(+)-1,1′-bi-2-naphthol in the presence of aq NaOH. This was also characterized by single crystal X-ray analysis. 相似文献
17.
Werner Schroth Ekkehard Hintzsche Roland Spitzner Dieter Str hl Katrin Schmei Joachim Sieler 《Tetrahedron》1995,51(48):13261-13270
3-exo,3′-exo-(1R,1′R)-bicamphor (12) is obtained from 3-exo,3′-exo-(1R,1′R)-bithtiocamphor (3) by condensation with hydrazine hydrate followed by hydrolysis of the resulting dihydropyridazine 11. Deprotonation of 12 with NaH and subsequent treatment with potassium hexacyanoferrate (III) furnishes the 2,2′-dioxo-3,3′-bibornanylidene 13, whilst reduction of 12 with L1AlH4 affords the 3,3′-biisoborneol 16. Further related transformations to various 2,2′-difunctional 3,3′-bibornane derivatives are described, which are could be of interest as chiral ligands 相似文献
18.
Abdelhak Benabra Ana Alcudia Noureddine Khiar Inmaculada Fernández Felipe Alcudia 《Tetrahedron: Asymmetry》1996,7(12):3353-3356
The stereochemical outcome of the reaction of chiral secondary alcohols with a phosphinyl chloride was found to be highly dependent on the achiral base used. Thus, the reaction of the readily available sugar derived carbinols, 1 and 2, with methylphenylphosphinyl chloride in the presence of triethylamine yields stereoselectively the corresponding Snp-phosphinates 3Sp and 5Sp in 94 and 92% diastereomeric excess (de). Simply changing the base from triethylamine to pyridine affords Rp-phosphinates 4Rp and 6Rp epimers to 3Sp and 5Sp at the phosphinyl phosphorus in 50 and 40% de respectively. These phosphinate esters were found to be good P-chiral transferring intermediates, they react with Grignard reagents under very mild conditions to give the corresponding phosphine oxides. Both enantiomers Sp- and Rp-o-anisylmethylphenylphosphine oxide (PAMPO) as well Sp- and Rp- methylphenylpropyl phosphine oxide were obained enantiomerically pure in high yields 相似文献
19.
Janet M. Snyder Jerry W. King Michael A. Jackson 《Journal of chromatography. A》1996,750(1-2):201-207
A method using sequential supercritical fluid extraction (SFE) and enzymatic transesterification has been developed for the rapid determination of total nutritional fat content in meat samples. SFE conditions of 12.16 MPa and 50°C were utilized to extract lipid species from the sample matrix. The enzymatic transesterification of the lipids by methanol was catalyzed by an immobilized lipase isolated from Candida antarctica. Conversion of the triglycerides to fatty acid methyl esters was monitored by supercritical fluid chromatography, while the fatty acid content of the extract was determined by capillary gas chromatography (GC). Total fat, saturated fat and monounsaturated fat contents were calculated from the GC data and compared to values from traditional extraction and lipid determination methods. Both off-line SFE and automated SFE followed by on-line GC analysis using two different instruments were utilized in this study. The enzymatic-based SFE method gave comparable results to the organic solvent extraction-based method followed by conventional BF3-catalyzed esterification. 相似文献
20.
Kunihiko Takabe Yasuhiro Iida Hidetaka Hiyoshi Masatoshi Ono Yoshihiko Hirose Yoshitaka Fukui Hidemi Yoda Nobuyuki Mase 《Tetrahedron: Asymmetry》2000,11(24):4825-4829
Enantioselective acetylation of 2-carbamoylmethyl-1,3-propanediol derivatives was catalyzed effectively by lipase PS to give monoacetates with high enantioselectivity: The enantioselectivity depended on the 2-carbamoylmethyl groups. The reaction of N-monoalkylcarbamoylmethyl-1,3-propanediol afforded the monoacetate with the (S)-configuration, whereas N,N-dialkylcarbamoylmethyl-1,3-propanediol gave the monoacetate with the (R)-configuration. 相似文献