Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Biotransformation enantioselective

Warner, N.A. Martin, J.W. Wong, C.S., Chiral polychlorinated biphenyls are biotransformed enantioselectively by mammalian c3tiochrome P-450 isozymes to form hydroxylated metabolites Environ. Sci Technol. 2009, 43, 114—121. [Pg.133]

Keywords Catalytic antibodies. Biotransformations, Enantioselective reactions. Transition state analogs. High throughput screening. [Pg.59]

Oxazolones (azlactones) are a form of activated lactones, so they are included in this section. CAL-B is an effective catalyst for the DKR of various racemic four-substituted-5 (4H)-oxazolones, in the presence of an alcohol, yielding optically active N-benzoyl amino acid esters as illustrated in Figure 6.24 [40]. Enantioselective biotransformations of lactides [72,73] and thiolactones ]74] have also been reported. [Pg.143]

The addition of HCN to aldehydes or ketones produces cyanohydrins (a-hydroxy nitriles). Cyanohydrins racemize under basic conditions through reversible loss of FiCN as illustrated in Figure 6.30. Enantiopure a-hydroxy acids can be obtained via the DKR of racemic cyanohydrins in the presence of an enantioselective nitriletransforming enzyme [86-88]. Many nitrile hydratases are metalloenzymes sensitive to cyanide and a nitrilase is usually used in this biotransformation. The DKR of mandelonitrile has been extended to an industrial process for the manufacture of (R)-mandelic acid [89]. [Pg.145]

Allen CCR, DR Boyd, H Dalton, ND Sharma, I Brannigan, NA Kerley, GN Sheldrake, SC Taylor (1995) Enantioselective bacterial biotransformation routes to cw-diol metabolites of monosubstituted benzenes, naphthalene and benzocycloalkenes of either absolute configuration. J Chem Soc Chem Commun 117-118. [Pg.394]

In some cases enzymes can increase the rate of reaction by up to lO times. Carnell and Roberts (1997) have briefly discussed the scope of biotransformations that are used to make pharmaceuticals like penicillins, cephalosporines, erythromycin, lovastatin, cyclosporin, etc., and for food additives like citric acid, L-glutamate, and L-lysine. A very successful transformation by Zeneca has been that of benzene reduction, with Pseudomonase Putida, to dihydrocatechol and catechol the dihydro derivative is used to produce (+/-) pinitol. Fluorobenzene has been converted to fluorodihydrocatechol, an intermediate for pharmaceuticals. The highly stereo selective Bayer-Villeger reaction has been carried out with genetically engineered S-cerevisvae. Hydrolases have allowed enantioselective, and in some cases regioselective, hydrolysis of racemic esters. [Pg.157]

Ernst, M., Kaup, B., Mueller, M. et al. (2005) Enantioselective reduction of carbonyl compounds by whole-cell biotransformation, combining a formate dehydrogenase and a (R)-specihc alcohol dehydrogenase. Applied Microbiology and Biotechnology, 66 (6), 629-634. [Pg.163]

Rhodococcus sp. AJ270 was applied to the transformation of a number of racemic cis- and traray-3-aryl-2-methyloxiranecarbonitriles (Figure 8.7). In all cases, the NHase activity proceeded very rapidly and with poor enantioselectivity. In contrast, the amidase activity was strongly dependent upon substrate structure. In general, the biocatalyst displays a strong preference for the unsubstituted phenyl side chain or /wa-substituted phenyl side chain compared with ortho- or meta-, and this is manifest both with respect to observed conversion and rate and also observed enantioselectivity. In contrast, the biotransformations of... [Pg.177]

Guo, X.-L., Deng, G., Xu, J. and Wang, M.-X. (2006) Immobilization of Rhodococcus sp. AJ270 in alginate capsules and its application in enantioselective biotransformation of ira/i.s-2-methyl-3- phenyl-oxiranecarbonitrile and amide. Enzyme and Microbial Technology, 39, 1-5. [Pg.194]

One of the most intriguing and best explored specificities of hydrolases is their product enantiospecificity, a property that is not restricted to the biotransformation of xenobiotics since it is displayed by lipases acting on their physiological substrates. Indeed, prochiral triglycerides have been found to be hydrolyzed with marked product enantioselectivity by various lipases [51] [52], Such specificity can hardly be fortuitous and must have a physiological significance, which remains to be understood. [Pg.398]

G. Bellucci, C. Chiappe, A. Cordoni, F. Marioni, The Rabbit Liver Microsomal Biotransformation of 1,1-Dialkylethylenes Enantioface Selection of Epoxidation and Enantioselectivity of Epoxide Hydrolysis , Chirality 1994, 6, 207 - 212. [Pg.674]

T. Ishida, T. Matsumoto, J. Caldwell, A. Drake, Enantioselective Biotransformation of Aryl-isopropyl, -isopropenyl, and -propenyl Groups by the Rabbit or by the Rat , Enantiomer 1998, 3, 133 - 147. [Pg.677]

Ulijn et al. identified an enzyme, capable of enantioselectively reducing the ketone, from their extensive collection of ADH variants further modification of the hit resulted in a biocatalyst that produces the desired (5)-alcohol in >99.9% ee at concentrations of 100 gL in a sofid-to-sofid biotransformation, where both starting material and product display only sparing solubility in the reaction medium. High conversions (>99%) are achieved by the substrate-coupled method, using 50 % v/v isopropyl alcohol concentrations to drive the reaction by continuous acetone removal (Scheme 1.55). The product can be easily isolated by filtration and washing. [Pg.51]

Gadler, P. and Faber, K., New enzymes for biotransformations microbial alkyl sulfatases displaying stereo- and enantioselectivity. Trends Biotechnol., 2007, 25, 83. [Pg.120]

The biotransformation of (/f,5)-Iinalool by fungi is a useful method for the preparation of natural linalool oxides. The stereospecific conversion of (J ,5)-linalool by Corynespora cassiicola DSM 62475 led to 5/f-configured furanoid linalool oxides and 55-configured pyranoid linalool oxides, both via bS -configured epoxylinalool as postulated intermediate (Figure 12.6). The biotransformation protocol affords an almost total conversion of the substrate with high enantioselectivities and a molar conversion yield close to 100% (Table 12.4). Pure linalool oxides are of interest for lavender notes in perfumery. ... [Pg.376]

The procedure is very easy to reproduce and to scale up. Bioconversion products can be easily isolated by evaporation of the extraction solvent (e.g. tert-butyl methyl ether). Table 12.4 summarizes the product concentrations, molecular conversion yields and enantioselectivities obtained during linalool biotransformation with C. cassiicola DSM 62475. [Pg.378]

This is the first time that the biotransformation of a-bromo and a,a -dibromo ketone using S. platensis has been successfully accomplished. Although enantioselective a-hydroxy ketones were not obtained, it was found that the hydroxylative biotransformation of a-bromo and o ,Q -(jibromo alkanones using S. platensis affords a new synthetic method, which is more convenient, cleaner, and of lower energy than the chemical method used heretofore (see Tables 12.7 and 12.8). Biotransformation for a-hydroxy ketone from a-bromo ketone is no doubt attributable to the special properties of S. platensis system. [Pg.395]

A strain of Pseudomonas aeruginosa has been recently described, which shows the opposite enantioselectivity, converting racemic arylaminonitriles efficientiy into the D-amino acids. Again, whole-cell biocatalysis worked well, the cells being entrapped in alginate beads. It is unclear whether this biotransformation involves an amide intermediate. [Pg.87]

J )-Mandelic acid 3 is a useful chiral synthon for the production of pharmaceuticals such as semi-synthetic penecillins, cephalosporins and antiobesity agents and many methods have been reported for the preparation of the optically pure material. A method to deracemize the racemate which is readily available on a large scale was developed by Ohta et al. using a combination of two biotransformations. The method consists of enantioselective oxidation of (S)-... [Pg.60]

Racemic warfarin (65), a vitamin K antagonist, has been used for decades both as an oral anticoagulant in man and as a rodenticide. The metabolism of this drug has been found to be substrate-enantioselective 9S-warfarin is considered as more active than the 9R-antipode. In mammalian systems, warfarin undergoes a stereoselective reduction of the ketonic side chain [176,177], affording mainly the 9R,llS-alcohol (71), but the major biotransformation route involves substrate-enantioselective aromatic hydroxylations at 4 -, 6-, 7- or 8-positions... [Pg.201]

Although [BMIM]BF4 has been evaluated as an isolation medium for lipase-catalyzed biotransformations, the general experience with it has not been favorable, relative to that with other ionic liquids, such as [BMIM]PF6. However, excellent performance was recently reported for [BDMIM]BF4 when it was used to host Candida antarctica (Novozym 435) for the enantioselective transesterification of 5-phenyl-l-penten-3-ol (+ and -) with vinyl acetate. The working hypothesis was that the oligomerization of acetaldehyde may be caused by the C2 proton of the [BMIM] ion because of the unfavorable acidity of this group (226). In contrast, the cation in [BDMIM]BF4 lacks this acidity. [Pg.226]

Promising developments of ionic liquids for biocatalysis reflect their enhanced thermal and operational stabilities, sometimes combined with high regio- or enantioselectivities. Ionic liquids are particularly attractive media for certain biotransformations of highly polar substrates, which cannot be performed in water owing to equilibrium limitations 297). [Pg.230]

Pirchanont et al. [333] proposed the use of RMs as a novel method for production of chiral epoxides. Mycobacterium sp. containing monooxygenase was employed as a biocatalyst and the potential of this method for chiral biotransformation was realized as superior to the conventional method. Another example for enantioselective reaction performed in RMs was provided by Buriak and Osborn [334]. [Pg.173]

The biosynthesis of many hydroxylated natural products proceeds through regio- and enantioselective modification of polyketides, which are assembled through chain elongation via acetate or propionate units [2]. The enzymes responsible for the chain elongation and subsequent reduction, elimination, aromatiza-tion, and further modifications are classified as polyketide synthases [3]. These multifunctional enzymes have been used for whole-cell biotransformation toward unnatural metabolites that are within the scope of combinatorial biosynthesis... [Pg.386]

Biooxidation of chiral sulfides was initially investigated in the 1960s, especially through the pioneering work of Henbest et al. [101]. Since then, many developments have been reported and are summarized in reviews [102,103], It would be helpful to reveal some structural or mechanistic details of enzymes involved in theoxidation processes. Biotransformations are also of great current interest for the preparation of chiral sulfoxides, which are useful as synthetic intermediates and chiral auxiliaries. Because extensive review of these transformations is beyond the scope of this chapter, only highlights are discussed in comparison with the abiotic enantioselective oxidations described earlier. Biooxidations by microorganisms and by isolated enzymes are discussed in Sections 6C.12.1. and 6C.12.2. [Pg.348]

Microbiological oxidation is the easiest procedure because it uses the intact cells. Scheme 6C. 11 shows results obtained by using Aspergillus Niger [101], Enantioselectivity can be very high but experiments are performed on a small scale, which results in a low yield of sulfoxides. Both enantiomers of methyl p-tolyl sulfoxide were prepared by Sih et al. with Mortierella isabellina NRRL 1757, giving (/ )-sulfoxide with 100% ee in 60% yield or with Helminthosporium sp NRRL 4671, giving (S)-sulfoxide with 100% ee in 50% yield [104], A similar result was obtained for ethyl p-tolyl sulfide. A predictive model for sulfoxidation by Helminthosporium sp NRRL 4671 was proposed by Holland et al. [105], which was based on the analysis of more than 90 biotransformations of sulfides. [Pg.349]


See other pages where Biotransformation enantioselective is mentioned: [Pg.101]    [Pg.101]    [Pg.158]    [Pg.123]    [Pg.139]    [Pg.144]    [Pg.162]    [Pg.265]    [Pg.109]    [Pg.339]    [Pg.194]    [Pg.229]    [Pg.7]    [Pg.36]    [Pg.344]    [Pg.385]    [Pg.4]    [Pg.60]    [Pg.155]    [Pg.110]    [Pg.155]    [Pg.541]    [Pg.27]    [Pg.255]   
See also in sourсe #XX -- [ Pg.82 , Pg.83 ]




SEARCH



Biotransformations enantioselective acylation

Biotransformations enantioselective hydrolysis reaction

Biotransformations enantioselective transformations

Nitriles enantioselective biotransformations

© 2024 chempedia.info