- Expanding the repertoire of nitrilases with broad substrate specificity and high substrate tolerance for biocatalytic applications
-
Enzymatic conversion of nitriles to carboxylic acids by nitrilases has gained significance in the green synthesis of several pharmaceutical precursors and fine chemicals. Although nitrilases from several sources have been characterized, there exists a scope for identifying broad spectrum nitrilases exhibiting higher substrate tolerance and better thermostability to develop industrially relevant biocatalytic processes. Through genome mining, we have identified nine novel nitrilase sequences from bacteria and evaluated their activity on a broad spectrum of 23 industrially relevant nitrile substrates. Nitrilases from Zobellia galactanivorans, Achromobacter insolitus and Cupriavidus necator were highly active on varying classes of nitriles and applied as whole cell biocatalysts in lab scale processes. Z. galactanivorans nitrilase could convert 4-cyanopyridine to achieve yields of 1.79 M isonicotinic acid within 3 h via fed-batch substrate addition. The nitrilase from A. insolitus could hydrolyze 630 mM iminodiacetonitrile at a fast rate, effecting 86 % conversion to iminodiacetic acid within 1 h. The arylaliphatic nitrilase from C. necator catalysed enantioselective hydrolysis of 740 mM mandelonitrile to (R)-mandelic acid in 4 h. Significantly high product yields suggest that these enzymes would be promising additions to the suite of nitrilases for upscale biocatalytic application.
- Rayavarapu, Pratima,Shah, Shikha,Sunder, Avinash Vellore,Wangikar, Pramod P.
-
p. 289 - 296
(2020/05/18)
-
- Degradation of bisphenol A and acute toxicity reduction by different thermo-tolerant ascomycete strains isolated from arid soils
-
Four different laccase-producing strains were isolated from arid soils and used for bisphenol A (BPA) degradation. These strains were identified as Chaetomium strumarium G5I, Thielavia arenaria CH9, Thielavia arenaria HJ22 and Thielavia arenaria SM1(III) by internal transcribed spacer 5.8 S rDNA analysis. Residual BPA was evaluated by HPLC analysis during 48 h of incubation. A complete removal of BPA was observed by the whole cell fungal cultures within different times, depending on each strain. C. strumarium G5I was the most efficient degrader, showing 100% of removal within 8 h of incubation. The degradation of BPA was accompanied by the production of laccase and dye decolorizing peroxidase (DyP) under degradation conditions. The presence of aminobenzotriazole (ABT) as an inhibitor of cytochrome P450s monooxygenases (CYP) demonstrated a slight decrease in BPA removal rate, suggesting the effective contribution of CYP in the conversion. The great involvement of laccase in BPA transformation together with cell-associated enzymes, such as CYP, was supported by the identification of hydroxylated metabolites by ultra-high performance liquid chromatography-mass spectroscopy (UHPLC-MS). The metabolic pathway of BPA transformation was proposed based on the detected metabolites. The acute toxicity of BPA and its products was investigated and showed a significant reduction, except for T. arenaria SM1(III) that did not caused reduction of toxicity (IC50 8%), possibly due to the presence of toxic metabolites. The results of the present study point out the potential application of the isolated ascomycetes in pollutant removal processes, especially C. strumarium G5I as an efficient degrader of BPA.
- Mtibaà, Rim,Olicón-Hernández, Dario Rafael,Pozo, Clementina,Nasri, Moncef,Mechichi, Tahar,González, Jesus,Aranda, Elisabet
-
-
- Ligand-Promoted, Boron-Mediated Chemoselective Carboxylic Acid Aldol Reaction
-
The first carboxylic acid selective aldol reaction mediated by boron compounds and a mild organic base (DBU) was developed. Inclusion of electron-withdrawing groups in the amino acid derivative ligands reacted with BH3·SMe2 forms a boron promoter with increased Lewis acidity at the boron atom and facilitated the carboxylic acid selective enolate formation, even in the presence of other carbonyl groups such as amides, esters, ketones, or aliphatic aldehydes. The remarkable ligand effect led to the broad substrate scope including biologically relevant compounds.
- Nagai, Hideoki,Morita, Yuya,Shimizu, Yohei,Kanai, Motomu
-
supporting information
p. 2276 - 2279
(2016/06/01)
-
- Homoserine lactone derivatives, preparation method thereof and pharmaceutical composition for prevention or treatment of the periodontal diseases containing the same as an active ingredient
-
The present invention relates to homoserine lactone derivatives, optical isomers of the same, or pharmaceutically acceptable salts of the same. The homoserine lactone derivatives in the present invention have excellent properties as a quorum sensing antagonist which hinders communications among bacteria. According to the present invention, the homoserine lactone derivatives can hinder gene expressions of bacteria while effectively blocking formation of biofilm which is known to raise resistance against antibiotics, and suppress propagation of bacteria, thereby being useful as a pharmaceutical composition for preventing or treating periodontal diseases.
- -
-
Paragraph 0152-0154
(2017/04/14)
-
- Evaluation of a new protocol for enzymatic dynamic kinetic resolution of 3-hydroxy-3-(aryl)propanoic acids
-
The application of tandem metal-enzyme dynamic kinetic resolution (DKR) is a powerful tool for the manufacture of high-value chemical commodities. A new protocol of kinetic resolution based on irreversible enzymatic esterification of carboxylic acids with orthoesters was introduced to obtain optically active β-hydroxy esters. This procedure was combined with metal catalyzed racemization of the target substrate providing both (R) and (S) enantiomers of ethyl 3-hydroxy-3-(4-nitrophenyl)propanoate with a high yield of 89% at 40°C. A substantial influence of the enzyme type, organic co-solvent, and metal catalyst on the conversion and enantioselectivity of the enzymatic dynamic kinetic resolution was noted.
- Koszelewski, Dominik,Zysk, Malgorzata,Brodzka, Anna,Zadlo, Anna,Paprocki, Daniel,Ostaszewski, Ryszard
-
p. 11014 - 11020
(2015/11/24)
-
- A high throughput screening strategy for the assessment of nitrile-hydrolyzing activity towards the production of enantiopure β-hydroxy acids
-
Nitrile hydrolysing enzymes have found wide use in the pharmaceutical industry for the production of fine chemicals. This work presents a strategy that facilitates the rapid identification of bacterial isolates demonstrating nitrile hydrolysing activity. The strategy incorporates toxicity, starvation and induction studies along with subsequent colorimetric screening for activity, further focusing the assessment towards the substrates of interest. This high-throughput strategy uses a 96 well plate system, and has enabled the rapid biocatalytic screening of 256 novel bacterial isolates towards β-hydroxynitriles. Results demonstrate the strategy's potential to rapidly assess a variety of β-hydroxynitriles including aliphatic, aromatic and dinitriles. A whole cell catalyst Rhodococcus erythropolis SET1 was identified and found to catalyse the hydrolysis of 3-hydroxybutyronitrile with remarkably high enantioselectivity under mild conditions, to afford (S)-3-hydroxybutyric acid in 42% yield and >99.9% ee. The biocatalytic capability of this strain including the variation of parameters such as temperature and time were further investigated and all results indicate the presence of a highly enantioselective if not enantiospecific nitrilase enzyme within the microbial whole cell.
- Coady, Tracey M.,Coffey, Lee V.,O'Reilly, Catherine,Owens, Erica B.,Lennon, Claire M.
-
p. 150 - 155
(2013/10/01)
-
- Synthesis and antitumour activity of β-hydroxyisovalerylshikonin analogues
-
A series of novel β-hydroxyisovalerylshikonin analogues bearing oxygen-containing substituents at the side-chain hydroxyl of shikonin were designed and synthesized. The cytotoxicities of these compounds were evaluated in vitro against multi-drug resistant (MDR) cell lines DU-145 and HeLa. Most compounds exhibited significant inhibitory activity on both cell lines. The structure-activity relationship showed the analogues with ether substituents displayed the most potent antitumour activity and selective cytotoxicity towards DU-145. Among the compounds with ether substituents, increasing the steric hindrance in the carbon bearing β-hydroxyl or replace the β-hydroxyl with acetoxy or methoxy would lead to the decline of cytotoxicity.
- Rao, Zhen,Liu, Xin,Zhou, Wen,Yi, Jing,Li, Shao-Shun
-
experimental part
p. 3934 - 3941
(2011/11/12)
-
- Acetic acid aldol reactions in the presence of trimethylsilyl trifluoromethanesulfonate
-
(Figure presented) In the presence of TMSOTf and a trialkylamine base, acetic acid undergoes aldol addition to non-enolizable aldehydes under exceptionally mild conditions. Acidic workup yields the β-hydroxy carboxylic acid. The reaction appears to procee
- Downey, C. Wade,Johnson, Miles W.,Lawrence, Daniel H.,Fleisher, Alan S.,Tracy, Kathryn J.
-
supporting information; experimental part
p. 5351 - 5354
(2010/10/20)
-
- Rhenium-catalyzed reaction of carbonyl compounds with ketene silyl acetals
-
It was found that rhenium complex is an effective catalyst for the reaction of carbonyl compounds with ketene silyl acetals. A wide range of β-silyloxy esters is obtained by the treatment of carbonyl compounds with ketene silyl acetals in the presence of
- Nishiyama, Yutaka,Kaiba, Kenta,Umeda, Rui
-
experimental part
p. 793 - 795
(2010/03/24)
-
- Highly anti-selective catalytic aldol reactions of amides with aldehydes
-
Barium phenoxide-catalyzed, highly anti-selective direct-type aldol reactions of amides with aldehydes have been developed. In the presence of a slight excess amount of an amide, the desired reactions proceeded smoothly under mild conditions, and a wide r
- Saito, Susumu,Kobayashi, Shu
-
p. 8704 - 8705
(2007/10/03)
-
- Exploring the synthetic applicability of a cyanobacterium nitrilase as catalyst for nitrile hydrolysis
-
The substrate specificity and synthetic applicability of the nitrilase from cyanobacterium Synechocystis sp. strain PCC 6803 have been examined. This nitrilase catalyzed the hydrolysis of both aromatic and aliphatic nitriles to the corresponding acids in high yields. Furthermore, the stereoselective hydrolysis of phenyl-substituted β-hydroxy nitriles to (S)-enriched β-hydroxy carboxylic acids and selective hydrolysis of α,ω- dinitriles with five or less methylene groups to ω-cyano carboxylic acids have been achieved. This suggested that nitrilase from Synechocystis sp. PCC 6803 could be a useful enzyme catalyst for the "green" nitrile hydrolysis. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Mukherjee, Chandrani,Zhu, Dunming,Biehl, Edward R.,Hua, Ling
-
p. 5238 - 5242
(2007/10/03)
-
- Facile deoxygenation of dicarbonyl compounds using a samarium diiodide-additive system
-
The reduction of α- and β-dicarbonyl compounds was investigated with samarium diiodide in the presence of additive. Diketones and ketocarboxylic acids were easily reduced at room temperature to give the mono-alcohols in good to excellent yield, and ketoester afforded the saturated ester as the major product in moderate yield. These reductions containing the reductive deoxygenation can be rapidly performed under the facile and mild conditions by this method.
- Kamochi, Yasuko,Kudo, Tadahiro,Masuda, Toshinobu,Takadate, Akira
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p. 1017 - 1020
(2007/10/03)
-
- A convenient generation of acetic acid dianion
-
The lithium enediolate of acetic acid can be generated efficiently, as a 0.5 M solution in THF, using lithium amides prepared from n-butyllithium in THF and either diethylamine or 1,3,3-trimethyl-6-azabicyclo-(3.2.1)-octane (AZA). Its reaction with carbon
- Parra, Margarita,Sotoca, Enrique,Gil, Salvador
-
p. 1386 - 1388
(2007/10/03)
-
- Direct catalytic aldol-type reactions using RCH2CN
-
(Matrix presented) A copper fluoride-catalyzed cyanomethylation that can be applied to a wide range of ketones and aldehydes was developed using TMSCH2CN as a nucleophile. The reaction was extended to a conceptually more advanced copper alkoxid
- Suto, Yutaka,Kumagai, Naoya,Matsunaga, Shigeki,Kanai, Motomu,Shibasaki, Masakatsu
-
p. 3147 - 3150
(2007/10/03)
-
- Synthesis of optically active 1,3-dioxin-4-one derivatives having a hydroxymethyl group at the 2-position and their use for regio-, diastereo-, and enantioselective synthesis of substituted cyclobutanols
-
A new method for preparing optically active 1,3-dioxin-4-one derivatives is presented. A series of prochiral 2,2-bis(hydroxymethyl)-1,3-dioxin-4-ones was synthesized by [4+2]cycloaddition of acylketene to protected 1,3-dihydroxy-2-propanone derivatives followed by deprotection of the hydroxyl groups. Desymmetrization of the prochiral dioxinones by lipase-catalyzed monoacetylation afforded optically active 2-(hydroxymethyl)dioxinones. Intramolecular photo[2+2]cycloaddition of ω-alkenyl esters of these alcohols provided an efficient method for regio-, diastereo-, and enantioselective synthesis of cyclobutanols.
- Murakami, Masayuki,Kamaya, Hiroshi,Kaneko, Chikara,Sato, Masayuki
-
p. 201 - 215
(2007/10/03)
-
- Lithium- α-lithioacetate and β-lithiopropionate: Useful intermediates in organic synthesis
-
The reaction of chloroacetic acid and 3-chloropropionic acid with a base (LDA or Bu(n)Li, respectively) and then with an excess of lithium and a catalytic amount of 4,4'-di-tert-butylbiphenyl (DTBB, 5%) in the presence of different electrophiles [Bu'CHO, PhCHO, Et2CO, (CH2)5CO, PhCOMe] in THF at -78°C leads, after hydrolysis with water, to the expected hydroxy acids, which in the second case are directly cyclised under acidic conditions to give the expected γ-lactones. (C) 2000 Elsevier Science Ltd.
- Pastor, Isidro M.,Yus, Miguel
-
p. 5335 - 5339
(2007/10/03)
-
- Polyphenolic glycosides from african proteaceae
-
The phytochemical investigation of members of the genus Protea afforded a series of polyphenolic compounds (1-5) that were identified by 1D and 2D NMR experiments. Of these, 2-5 are new compounds. Chemical syntheses of 1-3 were performed in order to confirm the structures and to prepare additional material for biological evaluation.
- Verotta,Orsini,Pelizzoni,Torri,Rogers
-
p. 1526 - 1531
(2007/10/03)
-
- Stereocontrol in organic synthesis using silicon-containing compounds. A formal synthesis of prostaglandins controlling the stereochemistry at C-15 using a silyl-to-hydroxy conversion following a stereochemically convergent synthesis of an allylsilane
-
Hydrosilylation of isoprene with chloro(diphenyl)silane gave (Z)-chloro(2-methylbut-2-enyl)-diphenylsilane 7. The cuprate reagent derived from this chloride underwent conjugate addition to methyl cinnamate 11, 1,2-silylcupration with hex-1-yne 16 and allene 18, and allylic displacement reactions with 1-vinylcyclohexyl acetate 20 and (Z)-1-cyclopentyloct-2-en-1-yl acetate 22. The silyl group in each of the products was converted into a hydroxy, with the removal of the 2-methylbut-2-enyl group taking place under much milder acidic conditions than those needed to remove the phenyl group from the dimethyl(phenyl)silyl group, and making this group suitable for the conversion of an allylsilane into an allyl alcohol. A stereospecifically anti conjugate displacement of the allylic benzoate group in (Z)-(1S,5R,6R,7R,1′S)-7-benzoyloxy-6-(1′-benzoyloxyoct-2′- enyl)-2-oxabicyclo[3.3.0]octan-3-one 52, and a stereospecifically syn conjugate displacement of the carbamate group in (Z)-(1S,5R,6R,7R,1′R)-7-benzoyloxy-6-(1′-N-phenylcarbamoyloxyoct- 2′-enyl)-2-oxabicyclo[3.3.0]octan-3-one 51, gave stereo-convergently the same allylsilane (1′ E,2″Z)-(1S,5S,6R,7R,3′S)-7-benzoyloxy-6-[3′-(2″- methylbut-2″-enyl)-diphenylsilyloct-1′-enyl]-2-oxabicyclo[3.3.0] octan-3-one 53. Silyl-to-hydroxy conversion gave the allyl alcohol (E)-(1S,5S,6R,7R,3′S)-7-benzoyloxy-6-(3′-hydroxyoct-1′-enyl)- 2-oxabicyclo[3.3.0]octan-3-one 54, having the relative and absolute stereochemistry at C-15 of the prostaglandins.
- Fleming, Ian,Winter, Stephen B. D.
-
p. 2687 - 2700
(2007/10/03)
-
- Samarium(II) iodide mediated intermolecular coupling reactions of N,N-dibenzyl-α-haloamides with carbonyl compounds
-
Samarium(II) iodide mediated coupling reactions of α-haloamides with carbonyl compounds are found to give N,N-dibenzyl-β-hydroxyamides (4a-i, 5a-i, and 6a) in good yields under mild reaction conditions. The transformation of 4a and 5a to N,N-dibenzyl-3-phenylpropanamide (7) and β-hydroxycarboxylic acid (8), respectively, are described.
- Aoyagi, Yutaka,Asakura, Rie,Kondoh, Nobuko,Yamamoto, Rieko,Kuromatsu, Takeshi,Shimura, Ai,Ohta, Akihiro
-
p. 970 - 974
(2007/10/03)
-
- Indenone synthesis. Improved synthetic protocol and effect of substitution on the intramolecular Friedel-Crafts acylation
-
An improved protocol for the construction of substituted indenones is presented. Also the effect of substitution on the intramolecular Friedel-Crafts acylation was noted. Specifically, if there is no substitution at the 2-position of the indenone poor yields of cyclized material were obtained, if at all, while the substitution of a methyl or ethyl group greatly improved the yield of cyclized material. Placement of a large group (e. g., benzyl) resulted in a diminuation of the improved yield. The new synthetic procedure could, in principle, allow for the construction of 2,3-disubstituted indenones. One example of this reaction mode was presented.
- Galatsis, Paul,Manwell, Jeffrey J.,Blackwell, James M.
-
p. 1656 - 1659
(2007/10/02)
-
- Influence of Nucleophiles on the High Temperature Aqueous Isomerization of cis- to trans-Cinnamic Acid
-
The rate of isomerization of cis- to trans-cinnamic acid in water at 195 deg C was monitored as a function of added nucleophile.The expected nucleophile addition products were not observed but could be synthesized and, when subjected to the reaction conditions, rapidly converted to trans-cinnamic acid.Deuterium labeling studies indicated that proton abstraction was not the rate-determining step, that the α-deuterium of α,β-dideuterio-cis-cinnamic acid was rapidly exchanged for an α-hydrogen atom without loss of the cis geometry, and that some direct isomerization of cis- to trans-cinnamic acid occured without the loss of vinyl deuterium atoms.The isomerization appears to involve an addition-elimination mechanism in the case of HO(1-) and HS(1-) ions, with the former more effective.Anthrahydroquinone ion was quite effective, meaning that it was a superior nucleophile or was promoting reactions by another mechanism (possibly electron tranfer chemistry).The results have bearing on the rate-determining step in one of the delignification mechanisms occurring during the pulping of wood.
- Reed, Gregg A.,Dimmel, Donald R.,Malcolm, Earl W.
-
p. 6364 - 6371
(2007/10/02)
-
- ENANTIOSELECTIVE SYNTHESIS OF α- AND β-HYDROXY ACIDS USING trans-2-PHENYLCYLOHEXAN-1-OL AS CHIRAL AUXILIARY
-
trans-2-Phenylcyclohexanol has been used as a chiral auxiliary for the preparation of α- and β-hydroxy acids in 85 - 100 percent and 11 - 89 percent enantiomeric purities respectively.
- Basavaiah, D.,Bharathi, T. K.
-
p. 3417 - 3420
(2007/10/02)
-
- TOWARDS CHIRAL REFORMATSKY REAGENTS
-
Chiral β-hydroxyacids are obtained via the Reformatsky reaction of lactic acid derivatives with carbonyl compounds in 11-100percent optical purities.
- Basavaiah, D.,Bharathi, T. K.
-
p. 2035 - 2040
(2007/10/02)
-
- STUDIES ON PIG LIVER ESTERASE-MEDIATED HYDROLYSES OF 3-HYDROXY ESTERS
-
At 25 deg C, the pig liver esterase (PLE)-catalyzed hydrolyses of 3-hydroxy esters 2 and 3 proceed in aqueous phosphate buffer with moderate enantioselectivity, which can be increased by carrying out the reaction in an aqueous medium containing 20percent
- Santaniello, Enzo,Ferraboschi, Patrizia,Grisenti, Paride,Manzocchi, Ada,Trave, Susanna
-
p. 581 - 584
(2007/10/02)
-
- (R)- AND (S)-2-ACETOXY-1,1,2-TRIPHENYLETHANOL - EFFECTIVE SYNTHETIC EQUIVALENTS OF A CHIRAL ACETATE ENOLATE
-
The enolate 3, easily available by double deprotonation of (R)-2-acetoxy-1,1,2-triphenylethanol (5), adds in a highly stereoselective manner to aldehides.Hydrolysis of the adducts 6/7 affods the acids 2.
- Braun, Manfred,Devant, Ralf
-
p. 5031 - 5034
(2007/10/02)
-
- Reduction of Substituted Δ2-Isoxazolines. Synthesis of β-Hydroxy Acid Derivatives
-
Three separate methods are reported for the formation of β-hydroxy acid derivatives from readily available substituted Δ2-isoxazolines.Cycloaddition of 2,2-dimethylpropanenitrile oxide with a variety of olefins followed by reductive cleavage produces α '-tert-butyl β-hydroxy ketones.These are cleaved to β-hydroxy tert-butyl esters by Baeyer-Villiger oxidation with peroxytrifluoroacetic acid.In the second approach, α ',β-dihydroxy ketones are generated via cycloaddition of olefins with the nitrile oxide generated from 2--2-methyl-1-nitropropane followed by reductive ring opening.Standard periodic acid cleavage gives β-hydroxy acids.Finally, 3-methoxy-substituted Δ2-isoxazolines, readily available via benzenesulfonylcarbonitrile oxide-olefin cycloaddition and methoxide displacement, are directly reduced to β-hydroxy esters.
- Curran, Dennis P.,Scanga, Susan A.,Fenk, Christopher J.
-
p. 3474 - 3478
(2007/10/02)
-
- β-Substituted Organolithium Compounds from Chlorohydrins: Application to the Direct Synthesis of Bifunctionalized Organic Cpmpounds
-
The reaction of different chlorohydrins with n-butyl-lithium at -78 deg C followed by metallation wiht lithium naphthalenide at the same temperature leads to very reactive organolithium compounds bearing an alkoxide function at the β-position with respect to metal.The reaction of these intermediates with several electriphiles leads to mono- as well as bi-functionalized organic compounds.Thus, treatment of these dianions with deuterium oxide, oxygen, carbon dioxide, benzyl bromide, dimethyl disulphide, and carbonyl compounds, gave 2-deuterioalcohols, 1,2-diols, β-hydroxy-acids, 2-benzyl alcohols, 2-hydroxy-thioethers, and 1,3-diols respectively.The preparation of β-substituted organolithium derivatives can be alternatively carried out starting from α-chloroketones by the same procedure.When the lithium atom is linked to a secondary carbon atom the dianions are very unstable and decompose, even at -100 deg C, by β-elimination yielding the corresponding olefins.
- Barluenga, Jose,Florez, Josefa,Yus, Miguel
-
p. 3019 - 3026
(2007/10/02)
-
- Methods for the Stereoselective Cis Cyanohydroxylation and Carboxyhydroxylation of Olefins
-
Two valuable reagents for the cis-specific vicinal cyanohydroxylation and carboxyhydroxylation of olefins are described.The cyanohydroxylation process is based on the decarboxylative ring opening of 3-carboxyisoxazolines prepared by the cycloaddition reaction of carbethoxyformonitrile oxide with various alkenes.Fragmentation of the isoxazolines prepared from cis- and trans-2-butene has been found to occur without any crossover in stereochemistry.The carboxyhydroxylation process begins with the dipolar cycloaddition reaction of the nitrile oxide derived from thetetrahydropyranyl ether derivative of 2-nitroethanol.Deprotection, hydrogenation, and oxitative cleavage of the derived dihydroxy ketone yield the stereochemcally pure β-hydroxy carboxylic acid.
- Kozikowski, Alan P.,Adamczyk, Maciej
-
p. 366 - 372
(2007/10/02)
-
- β-Substituted Organolithium Compounds; Direct Preparation and Reactivity
-
Very reactive organolithium compounds bearing an alkoxide function at the β-position with respect to the metal are obtained by direct metallation with lithium naphthalenide at low temperature of the corresponding lithium chlorohydrin salt; the reaction of these dianions with different electrophilic agents leads to the corresponding mono- and bi-functionalized compounds.
- Barluenga, Jose,Florez, Josefa,Yus, Miguel
-
p. 1153 - 1154
(2007/10/02)
-
- Mechanism of Hydrolysis of Hydroxy Thiolesters in the Presence of Boric Acid
-
The catalytic effect of boric acid on the hydrolysis of S-butyl 2-hydroxy-2-phenylthioacetate (thiomandelate, 1) and 3-hydroxy-3-phenylthiopropionate (2) has been investigated in aqueous solution.The catalytic constants increased sigmoidally with increasing pH, the pKa of the curve being 9.2 for both 1 and 2.Approximate Hammett ρ values were 1.2 and 0.6 for the alkaline and borate-catalyzed hydrolyses of ring-substituted derivatives of 1, respectively.Boric acid did not show any specific influence on the hydrazinolysis of 1.Thise results lead to the conclusion that the borate catalysis occurs through an intramolecular transfer of the boron-coordinated hydroxide ion to the carbonyl carbon within a borate-substrate complex.
- Okuyama, Tadashi,Nagamatsu, Hiroaki,Fueno, Takayuki
-
p. 1336 - 1342
(2007/10/02)
-
- Reaction de Reformatsky a froid avec des α-bromoesters-acetals. I. Une methode generale pour la synthese des β-hydroxyacides a partir des α-bromoesters de tetrahydropyrannyle (Note de laboratoire)
-
The readily accessible tetrahydropyranyl esters of α-bromoacids can be used in the Reformatsky reaction for the preparation of β-hydroxyacids.The reaction is generally carried out in cold tetrahydrofuran.The β-hydroxyacids can be easily obtained by stirring the cold solution of their tetrahydropyranyl esters with dilute hydrochloric acid.
- Bogavac, M.,Arsenijevic, L.,Arsenijevic, V.
-
p. 145 - 147
(2007/10/02)
-
- S-(4-chlorophenyl) 3-aryl-3-hydroxypropanethioates as antibacterial agents
-
A series of S-(4-chlorophenyl) 3-aryl-3-hydroxypropanethioates was prepared and shown to have in vitro activity against several selected bacterial species.
- Snyder Jr.,Burrous,Freedman,Herbert
-
p. 413 - 415
(2007/10/15)
-
- S-(4-Chlorophenyl)-3-aryl-3-hydroxypropanethioates
-
A series of S-(4-Chlorophenyl)-3-aryl-3-hydroxypropanethioates are effective as antibacterial agents.
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