- Molecular Gating of an Engineered Enzyme Captured in Real Time
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Enzyme engineering tends to focus on the design of active sites for the chemical steps, while the physical steps of the catalytic cycle are often overlooked. Tight binding of a substrate in an active site is beneficial for the chemical steps, whereas good accessibility benefits substrate binding and product release. Many enzymes control the accessibility of their active sites by molecular gates. Here we analyzed the dynamics of a molecular gate artificially introduced into an access tunnel of the most efficient haloalkane dehalogenase using pre-steady-state kinetics, single-molecule fluorescence spectroscopy, and molecular dynamics. Photoinduced electron-transfer-fluorescence correlation spectroscopy (PET-FCS) has enabled real-time observation of molecular gating at the single-molecule level with rate constants (kon = 1822 s-1, koff = 60 s-1) corresponding well with those from the pre-steady-state kinetics (k-1 = 1100 s-1, k1 = 20 s-1). The PET-FCS technique is used here to study the conformational dynamics in a soluble enzyme, thus demonstrating an additional application for this method. Engineering dynamical molecular gates represents a widely applicable strategy for designing efficient biocatalysts.
- Kokkonen, Piia,Sykora, Jan,Prokop, Zbynek,Ghose, Avisek,Bednar, David,Amaro, Mariana,Beerens, Koen,Bidmanova, Sarka,Slanska, Michaela,Brezovsky, Jan,Damborsky, Jiri,Hof, Martin
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Read Online
- Ni-Catalyzed Formal Cross-Electrophile Coupling of Alcohols with Aryl Halides
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Direct coupling of unactivated alcohols remains a challenge in current synthetic chemistry. We herein demonstrate a strategy building upon in situ halogenation/reductive coupling of alcohols with aryl halides to forge Csp2-Csp3 bonds. The combination of 2-chloro-3-ethylbenzo[d]oxazol-3-ium salt (CEBO) and TBAB as the mild bromination reagents enables rapid transformation of a wide range of alcohols to their bromide counterparts within one to 5 min in CH3CN and DMF, which is compatible with the Ni-catalyzed cross-electrophile coupling conditions in the presence of a chemical reductant. The present method is suitable for arylation of a myriad of structurally complex alcohols with no need for prepreparation of alkyl halides. More importantly, the mild and kinetically rapid bromination process has shown good selectivity in the bromination/arylation of symmetric diols and less sterically hindered hydroxyl groups in polyols, thus offering promise for selective functionalization of diols and polyols without laborious protecting/deprotecting operations. The practicality of this work is also evident in the arylation of a number of carbohydrates, drug compounds, and naturally occurring alcohols.
- Lin, Quan,Ma, Guobin,Gong, Hegui
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p. 14102 - 14109
(2021/11/20)
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- Acid-Catalyzed Intramolecular Ring-Opening Reactions of Cyclopropanated Oxabenzonorbornadienes with Carboxylic Acid Nucleophiles
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The present work demonstrates the ability of carboxylic acid tethered cyclopropanated oxabenzonorbornadienes (CPOBDs) to undergo ring-opening reactions in mild acidic conditions. The optimized reaction conditions involve the use of pTsOH in DCE at 90 °C. Two regioisomers are formed but the reactions are highly regioselective towards type 3 ring-opened products. It was observed that substitution at the C5 and aryl positions of CPOBD significantly hinders the ring-opening reactions leading to decreased yields of ring-opened products, although high regioselectivity for the Type 3 ring-opened products is still maintained. Herein, the first examples of acid-catalyzed intramolecular ring-opening reactions of CPOBD with carboxylic acid nucleophiles are reported.
- Carlson, Emily,Ho, Angel,Koh, Samuel,Macleod, Matthew P.,Pounder, Austin,Tam, William
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- An Ultrasensitive Fluorescence Assay for the Detection of Halides and Enzymatic Dehalogenation
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Halide assays are important for the study of enzymatic dehalogenation, a topic of great industrial and scientific importance. Here we describe the development of a very sensitive halide assay that can detect less than a picomole of bromide ions, making it very useful for quantifying enzymatic dehalogenation products. Halides are oxidised under mild conditions using the vanadium-dependent chloroperoxidase from Curvularia inaequalis, forming hypohalous acids that are detected using aminophenyl fluorescein. The assay is up to three orders of magnitude more sensitive than currently available alternatives, with detection limits of 20 nM for bromide and 1 μM for chloride and iodide. We demonstrate that the assay can be used to determine specific activities of dehalogenases and validate this by comparison to a well-established GC-MS method. This new assay will facilitate the identification and characterisation of novel dehalogenases and may also be of interest to those studying other halide-producing enzymes.
- Aslan-üzel, A?k?n S.,Beier, Andy,Ková?, David,Cziegler, Clemens,Padhi, Santosh K.,Schuiten, Eva D.,D?rr, Mark,B?ttcher, Dominique,Hollmann, Frank,Rudroff, Florian,Mihovilovic, Marko D.,Bury?ka, Tomá?,Damborsky, Ji?í,Prokop, Zbyněk,Badenhorst, Christoffel P. S.,Bornscheuer, Uwe T.
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p. 2032 - 2039
(2020/02/11)
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- Synthetic method of furazolidone metabolite AOZ
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The invention discloses a preparation method of 3-amino-2-oxazolidinone (AOZ). The method comprises the following steps: 1) carrying out a reaction on ethylene glycol and PBr3 to obtain 2-bromoethanol; 2) carrying out a substitution reaction on 2-bromoethanol and an alkali, then adding hydrazine hydrate into the system, continuously carrying out a ring-opening reaction, and removing excessive 2-bromoethanol and water after the reaction is completed to obtain an intermediate 2-hydrazinoethanol; and 3) in the presence of an alkali, carrying out a reaction on 2-hydrazinoethanol and diethyl carbonate to obtain 3-amino-2-oxazolidinone (AOZ). According to the method, a nitrofuran metabolite AOZ is synthesized by adopting a one-pot method at the rear half part, so that the loss of a separated andpurified sample in the synthesis process is greatly reduced.
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Paragraph 0022-0024
(2020/07/13)
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- Synthetic method of furazolidone metabolite AOZ
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The invention discloses a preparation method of 3-amino-2-oxazolidinone (AOZ). The method comprises the following steps: 1) carrying out a reaction on ethylene glycol and PBr3 to obtain 2-bromoethanol; 2) in the presence of an alkali, carrying out a reaction on NH2NH2Boc and 2-bromoethanol to obtain Boc protected 2-hydrazinoethanol; 3) in the presence of an alkali, carrying out a reaction on Boc protected 2-hydrazinoethanol and diethyl carbonate to obtain Boc protected 3-amino-2-oxazolidinone; and 4) performing deprotection on the Boc group in the Boc protected 3-amino-2-oxazolidinone to obtain 3-amino-2-oxazolidinone. According to the method, the yield of AOZ in the synthesis process is obviously increased, and separation and purification are facilitated.
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Paragraph 0028-0030
(2020/07/13)
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- 1,2-Dibromotetrachloroethane: An efficient reagent for many transformations by modified Appel reaction
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An efficient and facile method has been developed for the synthesis of alkyl bromides from various alcohols under mild conditions using a triphenylphosphine (PPh 3) /1,2-dibromotetrachloroethane (DBTCE) complex in excellent yields and very short time (5 min). This method can also be applied for the transformation of chiral alcohols to their corresponding bromides in very high enantiomeric excess. The PPh 3 /DBTCE complex is also successfully applied to ring-opening reactions of cyclic ethers in mild conditions. Esterification, amidation, and formation of acid anhydrides under very mild experimental conditions are also successfully accomplished by following a modification of the Appel reaction protocol in this work.
- Essiz, Sel?uk,Da?tan, Arif
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p. 150 - 156
(2019/05/16)
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- Method for preparing halogen ethyl alcohol and ethylene oxide
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The invention provides a method for preparing halogen ethyl alcohol. The method comprises the following step: (1) halogen alcoholization: adding halogen hydride, H2O2, ethylene and a Ti heteroatom-containing molecular sieve into a reaction device, and carrying out halogen alcoholization reaction to obtain the halogen ethyl alcohol. The invention also provides a method for preparing ethylene oxide with a halogenohydrin method. The method comprises the following steps: (1) halogen alcoholization: adding halogen hydride, H2O2, ethylene and a Ti heteroatom-containing molecular sieve into the reaction device, and carrying out the halogen alcoholization reaction to obtain the halogen ethyl alcohol; (2) saponification: carrying out saponification reaction on the halogen ethyl alcohol in the step (1) and a hydroxide of alkali metal, and separating to obtain the ethylene oxide and alkali halide metal salt; optionally (3) electroosmosis: carrying out bipolar membrane electroosmosis on alkali halide metal salt obtained in step (2) to obtain the hydroxide of alkali metal and the halogen hydride. According to the methods, the halogen ethyl alcohol or the ethylene oxide can be prepared at extremely high selectivity and yield, and the discharging of waste water and waste residues can be drastically lowered.
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Paragraph 0097; 0098; 0109; 0110; 0130; 0131
(2017/05/19)
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- Mechanism-guided design of flow systems for multicomponent reactions: Conversion of CO2 and olefins to cyclic carbonates
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A mechanism-guided design of a multi-step flow system enabled an efficient general process for the synthesis of cyclic carbonates from alkenes and CO 2. The flow system proved to be an ideal platform for multicomponent reactions because it was straightforward to introduce reagents at specific stages without their interacting with each other or with reaction intermediates prone to destruction by them. This system exhibited superior reactivity, increased yield, and broader substrate scope relative to conventional batch conditions and suppressed the formation of undesired byproducts, such as, epoxides and 1,2-dibromoalkanes. The Royal Society of Chemistry 2014.
- Wu, Jie,Kozak, Jennifer A.,Simeon, Fritz,Hatton, T. Alan,Jamison, Timothy F.
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p. 1227 - 1231
(2014/03/21)
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- Oxidative bromination of alkenes mediated with nitrite in ionic liquids
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The oxidative bromination of C2-C8 alkenes with HBr-NaNO2-O2 in solutions of BMImBr, HMImBr or BMImBF 4 containing 16-28 wt% H2O was studied using volumetric method, GC-MS analysis, 14N NMR and UV-VIS spectroscopy. The optimal conditions to conduct the reaction at high selectivity for 1,2-dibromoalkanes in BMImBr were determined. The composition of ionic liquid affects the catalytic performance. Although in BMImBF4 the reaction runs with equal rate as in bromide ionic liquid, the fraction of bromohydrin in the reaction products increases to 20 %. Generated from NaNO2, NOx operated as a catalyst in the oxidation of Br- and was oxidized to catalytically inert NO3 - anions when complete conversion of HBr was attained. Graphical Abstract: Oxidative bromination of alkenes [Figure not available: see fulltext.]
- Kuznetsova, Lidia I.,Kuznetsova, Nina I.,Zudin, Vladimir N.,Utkin, Viktor A.,Trebushat, Dmitry V.,Fedotov, Martin A.,Larina, Tatyana V.
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p. 1499 - 1506,8
(2014/11/08)
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- PHOTORESIST COMPOSITION, RESIST-PATTERN FORMING METHOD, POLYMER, AND COMPOUND
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A photoresist composition includes a polymer that includes a structural unit shown by the following formula (1), and a photoacid generator. R1 in the formula (1) represents a hydrogen atom, a fluorine atom, a methyl group, or a trifluoromethyl group, Z represents a group that forms a divalent alicyclic group having 3 to 20 carbon atoms together with a carbon atom bonded to X, X represents an alkanediyl group having 1 to 6 carbon atoms, Y represents a hydrogen atom or —CR2R3(OR4), and R2 to R4 independently represent a hydrogen atom or a monovalent hydrocarbon group, provided that R3 and R4 optionally bond to each other to form a cyclic ether structure together with a carbon atom bonded to R3 and an oxygen atom bonded to R4.
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- Improved synthesis of 2-(4-propylphenyl)ethanol
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A new procedure for the synthesis of 2-(4-propylphenyl)ethanol is provided. This new procedure significantly reduces side-products as 1-(4-propylphenyl) ethanol and 2-bromoethanol, which are obtained when using the previously known procedure. Only with the new procedure an efficient purification on the large scale needed for avoided-level-crossing muon-spin resonance experiments was possible. Structural details of the title compound could be derived from an X-ray structure analysis of a crystalline derivative, the nitrobenzoyl ester.
- Hashmi, A. Stephen K.,Burkert, Tobias,Bats, Jan W.,Martyniak, Aleksandra
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p. 179 - 181
(2007/10/03)
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- Synthesis of hydroxylated hydrocarbons
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Ethylene glycol, other diols, triols, and polyols are made in an efficient manner by reacting dibromides with water in the presence of a metal oxide. An integrated process of dibromide formation, alcohol synthesis, metal oxide regeneration, and bromine recycling is also provided.
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Page/Page column 5
(2008/06/13)
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- Unexpected selectivity in sodium borohydride reductions of α-substituted esters: Experimental and theoretical studies
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The propensity of sodium borohydride to reduce the carbonyl group in eleven α-substituted and two aromatic esters has been investigated by experiments and at the B3LYP/6-31++G(d,p)//HF/6-31G(d,p) level of theory. The chemoselectivities in nine of these reductions have been examined by experiments. Experimental results agree well with the calculated order of activation energies for hydride transfer to the ester carbonyl group. Methyl α-bromoacetate reduces faster than methyl α-fluoroacetate. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Li, Liang-Chun,Jiang, Ju-Xing,Ren, Jie,Ren, Yi,Pittman Jr., Charles U.,Zhu, Hua-Jie
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p. 1981 - 1990
(2007/10/03)
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- A mild, efficient, and inexpensive protocol for the selective deprotection of TBDMS ethers using KHSO4
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Potassium hydrogensulfate in 30% aq. methanol deprotects a variety of tert-butyldimethylsilyl ethers at room temperature in excellent yields.
- Arumugam, Pandurangan,Karthikeyan, Ganesan,Perumal, Paramasivan T.
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p. 1146 - 1147
(2007/10/03)
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- Kinetic study of the self-reactions of the BrCH2CH2O2 and BrCH(CH3CH(CH3O2 radicals between 275 and 373 K
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A conventional flash photolysis technique was used to measure the self-reaction rate constants of the primary BrCH2CH2O2 (2-bromoethylperoxy) and secondary BrCH(CH3)CH(CH3)O2 (2-bromo-l-methylpropylperoxy) β-brominated peroxy radicals, at temperatures in the range of 275-373 K. The absolute UV absorption spectra of BrCH2CH2O2 and BrCH(CH3)CH(CH3)O2 were also measured and compared to those obtained previously for these radicals. The temperature dependence of the self-reaction rate constants provided the following Arrhenius expressions: k(BrCH2CH2O2 + BrCH2CH2O2) = (6.15+5.152.99) × 10-14 exp{(1247 ± 203) K/T} cm3 molecule-1 s-1 and k(BrCH(CH3)CH(CH3)O2 + BrCH(CH3)CH(CH3)O2) = (7.60+22.05-5.65) × 10-15 exp{(1305 ± 428) K/T} cm3 molecule-1 s-1, where the uncertainties represent 95% confidence limits associated with the statistical fitting procedure and include the contribution for the expanded uncertainties in the individual rate constant. These results confirm the enhancement of the peroxy radical self-reaction reactivity upon β-substitution, which is similar for Br, Cl, or OH substituents. Structure-activity relationships are proposed for self-reactions of β-substituted peroxy radicals.
- Villenave, Eric,Moisan, Sandy,Lesclaux, Robert
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p. 2470 - 2477
(2007/10/03)
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- NOVEL HETEROCYCLIC COMPOUNDS HAVING ANTIDIABETIC, HYPOLIPIDAEMIC, ANTIHYPERTENSIVE PROPERTIES, PROCESS FOR THEIR PREPARATION AND PHARMACEUTICAL COMPOSITIONS CONTAINING THEM
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The present invention relates to novel antidiabetic compounds, their tautomeric forms, their derivatives, their stereoisomers, their polymorphs, their pharmaceutically acceptable salts, their pharmaceutically acceptable solvates and pharmaceutically acceptable compositions containing them. This invention particularly relates to novel azolidinedione derivatives of general formula (I), and their pharmaceutically acceptable salts, pharmaceutically acceptable solvates and pharmaceutical compositions containing them.
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- Azulene derivatives
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The invention provides novel azulene derivatives of general formula I wherein R1 to R6 have the significance given in the description, as well as their tautomers, enantiomers, diastereomers, racemates and physiologically compatible salts or esters and substances which are hydrolyzed or metabolized in vivo to compounds of formula I. The invention is also concerned with a process and intermediates for the manufacture of the above compounds, pharmaceutical compositions which contain such compounds as well as the use of these compounds in the treatment of inflammatory conditions.
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- Heterocyclic compounds having antidiabetic, hypolipidaemic, antihypertensive properties, process for their preparation and pharmaceutical compositions containing them
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The present invention relates to novel antidiabetic compounds, their tautomeric forms, their derivatives, their stereoisomers, their polymorphs, their pharmaceutically acceptable salts, their pharmaceutically acceptable solvates and pharmaceutically acceptable compositions containing them. This invention particularly relates to novel azolidinedione derivatives of the general formula (I), and their pharmaceutically acceptable salts, pharmaceutically acceptable solvates and pharmaceutical compositions containing them. STR1
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- Pseudophase Approach to Reactivity in Microemulsions: Quantitative Explanation of the Kinetics of the Nitrosation of Amines by Alkyl Nitrides in AOT/Isooctane/Water Microemulsions
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The kinetics of the nitroso group transfer from 2-ethoxyethyl (EEN) and 2-bromoethyl (BEN) nitrit+e to the secondary amines piperazine (PIP), N-methylbenzylamine (NMBA), and morpholine (MOR) in bis(2-ethylhexyl) sulfosuccinate (AOT)/isooctane(iC8)/water microemulsions were determined.They are explained quantitatively in terms of a model in which the reagents are distributed among the aqueous, organic, and AOT film surfactant, with the aqueous pseudophase and the surfactant film as the losi of the reaction.
- Garcia-Rio, L.,Leis, J. R.,Mejuto, J. C.
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p. 10981 - 10988
(2007/10/03)
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- Kinetics of the Reaction of Malononitrile with Alkyl Nitrites
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The reaction of malononitrile with aliphatic alkyl nitrites in aqueous basic media to give the corresponding oxime product HON=C(CN)2 goes through a mechanism involving a rate-limiting reaction between the alkyl nitrite and the carbanion CH(CN)2.
- Iglesias, Emilia
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- Reactivity of Nucleophilic Nitrogen Compounds towards the Nitroso Group
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We discuss the reactivity of 43 nucleophilic nitrogen compounds towards the nitroso group of N-methyl-N-nitrosotoluene-p-sulfonamide (MNTS), and in some cases with alkyl nitrites.The series of nucleophiles considered is structurally very varied, includes members exhibiting the alpha effect, and covers 8 pKa units and a range of reactivities of almost five orders of magnitude.The values of solvent isotope effects and activation parameters have been measured and throw light on the structure of the transition states involved.Reactivities do not correlate well with thebasicity of the nucleophile, largely owing to the behaviour of primary amines, ammonia and nucleophiles with an alpha effect.Application of the curve crossing model suggests a relationship with vertical ionization potentials.The relationship with Ritchie's N+ scale is discussed, and interesting correlations with the reactivities of the same nucleophiles in various other chemical processes are noted.
- Garcia-Rio, Luis,Iglesias, Emilia,Leis, J. Ramon,Pena, M. Elena,Rios, Ana
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- 2-Bromoethylperoxy and 2-Bromo-1-methylpropylperoxy Radicals: Ultraviolet Absorption Spectra and Self-reaction Rate Constants at 298 K
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The self-reaction rate constants and UV absorption spectra of two brominated peroxy radicals, BrCH2CH2O2 (2-bromoethylperoxy) and (CH3)BrCHCH(CH3)O2 (2-bromo-1-methylpropylperoxy) have been measured using the molecular modulation technique.Self-reaction rate constants (kobs) of (6.2 +/- 1.2) x 10-12 and (9.6 +/- 1.9) x 10-13 cm3 molecule-1 s-1 were obtained for BrCH2CH2O2 and (CH3)BrCHCH(CH3)O2, respectively.In both cases secondary chemistry is likely to enhance the removal rate of the radicals and the given rate constants are expected to be slightly higher than the true value.The UV spectra of both radicals are broad absorptions with maxima close to 240 nm.Absolute cross-sections at 270 nm were found to be (2.2 +/- 0.4) x 10-18 and (2.8 +/- 0.6) x 10-18 cm2 molecule-1 for BrCH2CH2O2 and (CH3)BrCHCH(CH3)O2, respectively.The measured values of self-reaction rate constants and UV absorption spectra are compared to results for C2H5O2.In addition, a long-lived transient absorption was observed in the BrCH2CH2O2 experiments, and is thought to be due to BrCH2CH2OOBr, a product of an association reaction between Br atoms and BrCH2CH2O2.
- Crowley, John N.,Moortgat, Geert K.
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p. 2437 - 2444
(2007/10/02)
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- Evidence for Concerted Acid Hydrolysis of Alkyl Nitrites
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The results of studying the acid hydrolysis of methyl, ethyl, isopropyl, butyl, tert-butyl, pentyl, 2-bromoethyl, 2-chloroethyl and 2-ethoxyethyl nitrites in water show that the reaction is not, as widely accepted in the literature, catalysed by nucleophiles (Cl-, Br-, etc.), but is however subject to general acid catalysis.These findings, and the observed values of the solvent isotope effect, suggest that the substrate is protonated in the rate-controlling step of the reaction.Further, the relative reactivities of the various substrates investigated suggest a concerted mechanism in which the proton transfer occurs concurrently with the breaking of the O-N bond via a slightly imbalanced transition state.
- Iglesias, Emilia,Garcia-Rio, Luis,Leis J. Ramon,Pena, M. Elena,Williams, D. Lyn H.
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p. 1673 - 1679
(2007/10/02)
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- FLASH VACUUM THERMOLYSIS OF 2-BROMOETHANOL. FORMATION OF &α-BROMOETHYLETHERS VIA 1-BROMOETHANOL.
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Flash Vacuum Thermolysis of 2-bromoethanol (2) leads to the quantitative formation of 1-bromo-1-(1-bromoethoxy)ethane (5, di-α-bromoethylether).Low temperature IR spectroscopy shows that 5 arises from the dimerization of 1-bromoethanol (3), which is observed below -100 deg C as the primary product.
- Jenneskens, Leonardus W.,Wiersum, Ulfert E.,Ripoll, Jean-Louis
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p. 6489 - 6492
(2007/10/02)
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- A PRACTICAL AND CONVENIENT SYNTHESIS OF THE NITROETHYLENE TRANSFER REAGENT, 2-NITROETHYL PHENYL SULFOXIDE
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A safe and practical route to the nitroethylene transfer reagent, 2-nitroethylphenyl sulfoxide, involving sodium nitrite-DMSO, for the introduction of the nitro function, is described.
- Ranganathan, S.,Ranganathan, D.,Singh, S.K.
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p. 2893 - 2894
(2007/10/02)
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- Antiprotozoal diamidines
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Diamidines of the formula STR1 wherein X is a propylene, isobutylene, guanidine, pyrrole, tetrazole, imidazole or substituted imidazole group; and 2-[4-(2-imidazolinyl)phenyl]-6-(2-imidazolinyl)indole, are useful in the treatment of certain protozoal infections in mammals, particularly in cattle.
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- An Effective Method for the Preparation of ω-Bromoalkanols from α,ω-Diols
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Pure ω-bromoalkanols 2 (n=2-12), not contaminated by any dibromoalkanes or unreacted diols 1, were prepared in good yields by refluxing a mixture of diols 1, aqueous (48percent) hydrogen bromide, and benzene using a Dean-Stark water separator.
- Kang, Suk-Ku,Kim, Won-Sup,Moon, Byoung-Ho
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p. 1161 - 1162
(2007/10/02)
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- Sulfur-containing phospholipid compounds and therapeutic compositions
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Sulfur-containing phospholipid compounds of the formula STR1 pharmaceutical compositions having anti-tumor activity which include said phospholipid compounds, and the method of use for combating tumors, of said phospholipid compounds.
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- Effects of Volume and Surface Property in Hydrolysis by Acetylcholinesterase. The Trimethyl Site
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β-Substituted ethyl acetates, XCH2CH2OCOCH3, have been prepared, and their hydrolysis by acetylcholinesterase has been studied.Log of enzymic reactivity, normalized for intrinsic reactivity in hydrolysis by hydroxide, log(kcat/Km)n, rises linearly with increasing refraction volume, MR (or RD25), for substrates with β-X = H, Cl, Br, CH3CH2, (CH3)2CH, (CH3)2S+, (CH3)3N+, and (CH3)3C.Larger substituents may by accommodated, (CH3)3Si and (CH3CH2)3N+, with no further increase in rate.Substrates with β-substituents CH3S, CH3S(O), (CH3)3N+(OH), and CH3S(O2) are less reactive than consistent with the relation with MR by factors of 5-40, indicating that hydrophobic surface and desolvation of the substrate-enzyme interface may be necessary for maximum reactivity correlated with MR.Values of log (kcat/Km)n for substrates with β-substituents X = CH3S, Cl, Br, CH3CH2, (CH3)2CH, (CH3)3C, and (CH3)3Si rise linearly with increasing hydrophobicity, ?, but reactivity of substrates with X = (CH3)3N+ and (CH3)2S+ are more reactive than consistent with a relation to ? by factors of 300 and 40 and with X = CH3S(O2), CH3S(O), and (CH3)2N+(OH), by factors of 7-100.Reactivity appears related to (i) volume of the β-substituent and its fit in its subsite, which is trimethyl rather than anionic, and (ii) the hydrophobicity of its surface.
- Cohen, Saul G.,Elkind, Jerome L.,Chishti, S. Bano,Giner, Jose-L. P.,Reese, Heide,Cohen, Jonathan B.
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p. 1643 - 1647
(2007/10/02)
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- Hair dye compositions and new compounds useful therein
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Novel compounds of the general formula STR1 wherein Z represents a substituted lower alkyl radical; each of R1 and R2 is hydrogen atom, a lower alkyl or a substituted lower alkyl identical with or different from Z and the functional groups NO2 and NR1 R2 can occupy all ring positions in relation to OZ, with the exception that if Z is β-hydroxyethyl, --NO2 is in the 4 position and --N(R1)(R2) is in the 2 position then either R1 or R2 is other than hydrogen. The novel compounds are for dyeing human hair in a variety of yellow shades. The compounds of formula (I) may be used as aqueous or water-alcohol solutions to form dye compositions for dyeing human hair.
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- Pyrido[3,2,1-jk]carbazols
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A pyrido[3,2,1-jk]carbazol derivative represented by the formula (I) STR1 wherein R represents a hydroxy group, an alkoxy group which may be substituted with a halogen atom or with a 4-methyl-1-piperidinyl group, a hydrazino group or a STR2 group, Y represents an alkoxy group, a halogen atom, a nitro group, an amino group, an alkanoylamino group or alkyl group, and n is 0, 1 or 2; and the pharmaceutically acceptable salts thereof having antimicrobial, anti-cancer and antiviral activities, and a process for preparing the same.
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