Reactions In Organic Media Research Articles

Biocatalytic Reactions in Organic media by using Lipid-coated Enzymes.

A new way of solubilizing hydrolytic enzymes in organic media was achieved by coating the enzyme with lipid monolayers. Lipid-coated enzymes have been used successfully for a number of types of reactions in organic media or organic-aqueous two-phases, for example, enantioselective esterification by lipase, transphosphatidylation of water-insoluble phospholipids by phospholipase D, hydrolysis of lipophilic substrates by a catalytic antibody, and transglycosylation by β-D-galactosidase.

The enantiomeric purity of alcohols formed by enzymatic reduction of ketones can be improved by optimisation of the temperature and by using a high co-substrate concentration

The stereoselective reduction of ketones by alcohol dehydrogenase from Thermoanaerobium brockii was studied in organic reaction media. 2-Propanol was used as co-substrate to regenerate the coenzyme NADPH. The enantiomeric excess of the alcohol formed from the ketone decreased during the course of the reaction (from 53 to 0% e.e. in the formation of ( R)-2-butanol). This was interpreted as being due to the reversibility of all the reactions involved. By using a large excess of 2-propanol this effect was suppressed. In the reduction of 2-butanone to ( R)-2-butanol, the enantiomeric excess increased with increasing temperature, but in the reduction of 2-pentanone to ( S)-2-pentanol the enantiomeric excess decreased with increasing temperature. The data were evaluated in terms of free energy of activation of the reaction pathways leading to the different possible products.

Lipid-coated enzymes as efficient catalysts in organic media

A new way of solubilizing hydrolytic enzymes so that they can be used in organic solvents is to coat them with lipid monolayers. Lipid-coated enzymes have been used successfully for a number of different types of reactions in organic media or organic-aqueous, two-phase systems; for example, enantioselective esterification by lipase, transphosphatidylation of water-insoluble phospholipids by phospholipase D, hydrolysis of a lipophilic substrate by a catalytic antibody and transglycosylation by β-d-galactosidase.

Enzymatic esterification reaction in organic media with continuous water stripping: effect of water content on reactor performance and enzyme agglomeration

A water removal system with in situ monitoring of the reaction medium turbidity was used to investigate the effect of water content on reactor performance and enzyme agglomeration. The performance of the system was tested by carrying out the lipase-catalyzed esterification of caprylic acid and n-butanol in cyclohexane. Enzyme agglomeration strongly depended on the water content in the solvent medium. By preventing agglomeration, the reactor could be operated in a continuous mode for 150 h without any loss of enzyme reactivity, whereas insufficient water stripping resulted in a gradual decrease of the conversion due to agglomeration of enzyme.

Catalytic Activity of Lipid-coated Enzymes in Organic Media.

A new way of solubilizing hydrolytic enzymes in organic media was achieved by coating the enzyme with lipid monolayers. Lipid-coated enzymes have been used successfully for a number of types of reactions in organic media or organic-aqueous two-phases, for example enantioselective esterification by lipase, transphosphatidylation of water-insoluble phospholipids by phospholipase D, hydrolysis of a lipophilic substrate by a catalytic antibody, and transglycosylation by, β-D-galactosidase.

Catalytic conversions in water. Part 6. A novel biphasic hydrocarboxylation of olefins catalyzed by palladium TPPTS complexes (TPPTS=P(C6H4-m-SO3Na) 3)

Exceptionally high catalytic activities (TOF>2500 h-1) have been achieved in the biphasic hydrocarboxylation of propene catalysed by water-soluble Pd/TPPTS complexes. The activity was even higher than that exhibited by organic-soluble Pd/PPh3 systems. This contrasts with the general perception that biphasic catalysis normally exhibits lower rates compared to analogous reactions in organic media. The hydrocarboxylation of 4-isobutylstyrene to ibuprofen and of styrene in a two-phase system is also reported.

Enzymatic reactions in organic media Edited by A. M. P. Koskinen and A. M. Klibanov. Blackie Academic & Professional, Glasgow, 1995. pp. xiii+314, price £75.00. ISBN 0-7514-0259-1

Polymer InternationalVolume 42, Issue 1 p. 128-128 Book Review Enzymatic reactions in organic media Edited by A. M. P. Koskinen and A. M. Klibanov. Blackie Academic & Professional, Glasgow, 1995. pp. xiii+314, price £75.00. ISBN 0-7514-0259-1 G. Jackers, G. JackersSearch for more papers by this authorJ. F. Kennedy, J. F. KennedySearch for more papers by this author G. Jackers, G. JackersSearch for more papers by this authorJ. F. Kennedy, J. F. KennedySearch for more papers by this author First published: 26 March 1999 https://doi.org/10.1002/(SICI)1097-0126(199701)42:1<128::AID-PI673>3.0.CO;2-CAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume42, Issue1January 1997Pages 128-128 RelatedInformation

A novel synthesis of allyl and propargyl selenides in aqueous media promoted by indium

Allylic and propargyl bromides react smoothly with diorganyl diselenides in aqueous media to give allylic and propargyl selenides in moderate to good yields. The reaction need not be carried out in inert atmosphere. The speed is quicker than the same reactions in organic media.

Microwave radiation can increase the rate of enzyme-catalysed reactions in organic media

Irradiating a hydrated lipase enzyme suspended in organic media using microwaves (2.45 GHz, 50°C) enhanced the reaction rate by 2–3 fold over classical heating and the apparent non-thermal effects observed were dependent on the hydration state of the enzyme in the organic medium.

Temperature effects on protease catalyzed acyl transfer reactions in organic media

The influence of reaction temperature on synthesis activity, product yield and nucleophile specificity for α-chymotrypsin and subtilisin Carlsberg were studied. The enzymes were immobilized on Celite and used in acetonitrile with a water content of 10%. Acyl-transfer reactions with Ac-PheOEt as acyl donor and 11 different amino acid amides and 3 dipeptides as nucleophiles were studied. The decrease in temperature from 25 to −1°C had a positive effect on the peptide yield in all reactions studied. The most efficient nucleophiles for the two enzymes α-chymotrypsin and subtilisin Carlsberg is arginine amide and glycine amide, respectively. When decreasing the reaction temperature the yield for α-chymotrypsin increased from 86 to 94% with arginine amide as nucleophile and for subtilisin the yield increased from 75 to 84% for glycine amide. The nucleophile specificity was determined as the p value, which describes the competition between nucleophile and water for the acyl enzyme. α-Chymotrypsin showed preference for both small and positively charged amino acid residues and subtilisin preferred small uncharged nucleophiles. The temperature did not affect the specificity order but all nucleophiles became more effective in the competition with water at low temperature. In addition, the results indicate that the temperature effect is more pronounced for the smaller nucleophiles.

ChemInform Abstract: Activity and Enantioselectivity of Serine Proteases in Transesterification Reactions in Organic Media

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Resolution of a tetrahydrofuran ester by Candida rugosa lipase (CRL) and an examination of CRL's stereochemical preference in organic media

Abstract Crude lipase from Candida rugosa (CRL) is able to resolve the C3-stereoisomers of the furo[2,3b]furan building block methyl 2-methoxytetrahydrofuran-3-carboxylate 6 by alcoholysis using n -butanol in octane. The reaction is not affected by the configuration at C2. The absolute configuration of the product 7 is 3S as determined by X-ray analysis of the crystalline derivative 14 . The stereochemical outcome of the reaction is compared to the active site model derived by the group of Kazlauskas (Ahmed et al., Biocatalysis 9 (1994), 209). Evidence is presented for the validity of this model for CRL-catalyzed alcoholysis, esterification and acidolysis reactions in organic media.

Reaction of 5-bromomethylfluorescein (5-BMF) with cefuroxime and other carboxyl-containing analytes to form derivatives suitable for laser-induced fluorescence detection

The aim of this work was to evaluate the reactivity of 5-bromomethylfluorescein (5-BMF), a relatively new absorbance and fluorescence derivatization reagent, toward various classes of carboxylic acids. The model analytes included cefuroxime and benzoic acid (aromatic monocarboxylic acid), oleic acid and prostaglandin (unsaturated carboxylic acids), adipic acid and suberic acid (aliphatic dicarboxylic acids), palmitic acid and γ-cholesteryloxybutyric acid (CBA; aliphatic saturated carboxylic acids). Confirmation of conjugate formation was performed using TLC, HPLC and/or electrospray ionization mass spectrometry (ESI–MS). The yields of example conjugates were maximized using a sequential single factor approach. The conjugate of cefuroxime appeared to form via an intermediate. Palmitic acid produced two distinct conjugates; oleic acid and prostaglandin E2 produced single derivatives. CBA was derivatized to form a highly hydrophobic conjugate. 5-BMF failed to form a conjugate with benzoic acid, and dicarboxylic acids. This may have been due to the formation of intermolecular complexes or highly polar salts of the acids, which were insoluble in the organic reaction medium. The conjugates were monitored by UV absorbance, fluorescence and argon ion laser-induced fluorescence (LIF). 5-BMF was found to be a suitable reagent for LIF detection of the stated analytes.

Effects of crown ethers and small amounts of cosolvent on the activity and enantioselectivity of α-chymotrypsin in organic sofvents

Abstract

Hydroxylation of phenolic compounds

Phenolic compounds, e.g., the phenols and phenol ethers, are selectively hydroxylated whereby the amounts of the final product para isomer are enhanced, for example in favor of hydroquinone versus pyrocatechol in the event of the hydroxylation of phenol, by reacting such phenolic compounds with hydrogen peroxide, advantageously in a polar, aprotic, organic solvent reaction medium, in the presence of a catalytically effective amount of a sulfonated polymer and a cocatalytically effective amount of an aromatic ketone compound.

Sol-gel entrapment of lipase using a mixture of tetramethoxysilane and methyltrimethoxysilane as the alkoxide precursor: Esterification activity in organic media

The sol-gel method, using a mixture of tetramethoxysilane (TMOS) and methyltrimethoxysilane (MTrMOS) as the silicon alkoxide precursor, has been applied to entrapment of lipase catalyzing esterification reactions in organic media. Increasing molar ratio of MTrMOS to TMOS led to formation of opaque and non-shrinkable gels and resulted in an increase in the esterification activity of lipase. The hybrid gel-entrapped lipase based on [MTrMOS]/[TMOS] ratio of 4 exhibited almost equal activity with those of the deposited lipase on different supports at 35°C, and retained ca. ten times higher activity than the deposited counterparts at 65 °C.

Kinetics of acyl transfer reactions in organic media catalysed by Candida antarctica lipase B

The acyl transfer reactions catalysed by Candida antarctica lipase B in organic media followed a bi-bi ping-pong mechanism, with competitive substrate inhibition by the alcohols used as acyl acceptors. The effect of organic solvents on V m and K m was investigated. The V m values in acetonitrile was 40–50% of those in heptane. High K m values in acetonitrile compared to those in heptane could partly be explained by an increased solvation of the substrates in acetonitrile. Substrate solvation caused a 10-fold change in substrate specificity, defined as ( V m/ K m)ethyloctanoate/( V m/ K m)octanoicacid, going from heptane to acetonitrile. Deacylation was the rate determining step for the acyl transfer in heptane with vinyl- and ethyl octanoate as acyl donors and ( R)-2-octanol as acyl acceptor. With 1-octanol, a rate determining deacylation step in heptane was indicated using the same acyl donors. Using 1-octanol as acceptor in heptane, S-ethyl thiooctanoate had a 25- to 30-fold lower V m/ K m value and vinyl octanoate a 4-fold higher V m/ K m value than that for ethyl octanoate. The difference showed to be a Km effect for vinyl octanoate and mainly a K m effect for S-ethyl thiooctanoate. The V m values of the esterification of octanoic acid with different alcohols was 10–30-times lower than those for the corresponding transesterification of ethyl octanoate. The low activity could be explained by a low pH around the enzyme caused by the acid or a withdrawing of active enzyme by nonproductive binding by the acid.

Alteration of the activity and selectivity of immobilized lipases by the effect of the amount of water in the organic medium

Lipase from Candida cylindracea has been covalently immobilized on agarose, silica and alumina. These enzymatic derivatives are inactive in synthesis after lyophilization (48 h) if an aqueous buffer is not added to the organic reaction medium. The addition of water restores the enzymatic activity of the immobilized lipase on agarose, but not on hydrophobic supports such as silica or alumina. Unlyophilized derivative on silica is more stable and active than the native enzyme in its optimum hydration conditions. In the esterification of racemic ibuprofen in isooctane, native and immobilized lipases are selective towards the S(+) enantiomer. Immobilized lipase on silica and native lipase have the same synthetic activity and selectivity, but the immobilized derivative is four times more stable at 25°C than its soluble counterpart.

Activity and enantioselectivity of serine proteases in transesterification reactions in organic media

The activity and enantioselectivity of α-chymotrypsin and subtilisin Carlsberg in the transesterification of a series of N-acetyl-alanine and -phenylalanine esters in cyclohexane were investigated at constant water activity, both in the absence and presence of 18-crown-6. Isosteric variation of the leaving ability of the alcoholate group in the substrates by fluoro substitution provided information about the acylation step of the reaction. For less reactive esters, the rate of acylation is determined by expulsion of the leaving group, whereas for activated esters the rate is dictated by a physical step, most likely a relatively slow conformational change of the enzyme. This makes the enantioselectivity of the enzymes strongly dependent of the substrate activity and the composition of the reaction medium. The catalytic effect of 18-crown-6, observed for all reactions. can be attributed to an enhanced enzyme-substrate binding and an increase of the rate of acylation.

Continuous control of water activity during biocatalysis in organic media

This paper describes a newly developed technique to adjust and control the water activity in enzymatic reactions in organic media. A saturated salt solution of known water activity is circulated inside a silicone tube, submerged into the reaction medium. The circulating solution can both absorb and release water. Water activity control during lipase catalyzed esterification was demonstrated with diisopropyl ether as solvent.