Altering the Substrate Specificity of Reductase CgKR1 from Candida glabrata by Protein Engineering for Bioreduction of Aromatic α‐Keto Esters

A versatile keto ester reductase CgKR1, exhibiting a broad substrate spectrum, was obtained from Candida glabrata by genome data mining. It showed the highest activity toward an aliphatic β‐keto ester, ethyl 4‐chloro‐3‐oxobutanoate (COBE), but much lower activity toward bulkier α‐keto esters with an aromatic group, such as methyl ortho‐chlorobenzoylformate (CBFM) and ethyl 2‐oxo‐4‐phenylbutyrate (OPBE). By rational design of the active pocket, the substrate specificity of the reductase was significantly altered and this tailor‐made reductase showed a much higher activity toward aromatic α‐keto esters (∼7‐fold increase in k_cat/K_m toward CBFM) and lower activity toward aliphatic keto esters (∼12‐fold decrease in k_cat/K_m toward COBE). Meanwhile, the thermostability of the reductase was enhanced by a consensus approach. Such improvements may yield practical catalysts for the asymmetric bioreduction of these aromatic α‐keto esters

     

Catalytic Hydrogenation of α‐Iminophosphonates as a Method for the Synthesis of Racemic and Optically Active α‐Aminophosphonates

It was shown that the catalytic hydrogenation of α‐iminophosphonates by molecular hydrogen can serve as a convenient method for the synthesis of racemic and optically active α‐aminophosphonates. Up to 94% ee was achieved in the rhodium‐catalyzed enantioselective hydrogenation using chiral ligand (R)‐BINAP.     

An efficient catalyst system for the carbonylation to esters of α-arylpropionic acids

The polymer-supported bimetallic catalyst system PVP–PdCl₂–CuCl₂/PPh₃ has good conversion and regioselectivity to carbonylation of α-(6′-methoxy-2′-naphthyl)ethanol under mild conditions. The effects of temperature, CO pressure, reaction time and P/Pd ratio have been studied to obtain optimum reaction conditions. The carbonylation of various α-arylethanols and styrene derivatives are also investigated with the same catalyst. X-ray photoelectron spectroscopy (XPS) and transmission electron micrograph (TEM) show that the polymer would protect palladium particles against aggregation and serve as a ligand.     

C‐3 Selective Ring Opening of 2,3‐Aziridino Alcohols and their Derivatives with Nucleophiles in the Presence of β‐Cyclodextrin in Water

For the first time a mild and efficient procedure has been developed for the C‐3 selective ring opening, under biomimetic conditions, of 2,3‐aziridino alcohols and their derivatives with nucleophiles such as aromatic thiols and amines catalyzed by β‐cyclodextrin in water at room temperature to afford the corresponding β‐amino sulfides and diamines with high regioselectivity in impressive yields. The use of cyclodextrin precludes the use of either acid or base and the catalyst can be recovered and reused.     

Commercial synthesis of α-D-cellobiosyl bromide heptaacetate

A detailed commercial process for the synthesis and purification of the activated disaccharide, α-D -cellobiosyl bromide heptaacetate ( 1 ) was developed. Reaction of α-D -cellobiose octaacetate (CBO) with HBr in glacial acetic acid or in glacial acetic acid/methylene chloride combination affords α-D -cellobiosyl bromide heptaacetate in high yield and excellent quality. Process variables such as reaction solvent, reaction time, reaction temperature, HBr stoichiometry, isolation methods and product purification options were optimized for large-scale synthesis. α-D -Cellobiosyl bromide heptaacetate was successfully prepared in a commercial manufacturing plant.     

Direct Decarboxylative Alkynylation of α,α‐Difluoroarylacetic Acids under Transition Metal‐Free Conditions

An efficient and generally applicable protocol for decarboxylative coupling of α,α‐difluoroarylacetic acids with ethynylbenziodoxolone (EBX) reagents has been developed, affording α,α‐difluoromethylated alkynes bearing various functional groups in moderate to excellent yields. Remarkably, this potassium persulfate (K₂S₂O₈)‐promoted reaction employs water as solvent under transition metal‐free conditions, thus providing a green synthetic approach to α,α‐difluoromethylated alkynes.

     

Chemical Synthesis of Rare Natural Bile Acids: 11α‐Hydroxy Derivatives of Lithocholic and Chenodeoxycholic Acids

A method for the preparation of 11α‐hydroxy derivatives of lithocholic and chenodeoxycholic acids, recently discovered to be natural bile acids, is described. The principal reactions involved were (1) elimination of the 12α‐mesyloxy group of the methyl esters of 3α‐acetate‐12α‐mesylate and 3α,7α‐diacetate‐12α‐mesylate derivatives of deoxycholic acid and cholic acid with potassium acetate/hexamethylphosphoramide; (2) simultaneous reduction/hydrolysis of the resulting △¹¹‐3α‐acetoxy and △¹¹‐3α,7α‐diacetoxy methyl esters with lithium aluminum hydride; (3) stereoselective 11α‐hydroxylation of the △¹¹‐3α,24‐diol and △¹¹‐3α,7α,24‐triol intermediates with B₂H₆/tetrahydrofuran (THF); and (4) selective oxidation at C‐24 of the resulting 3α,11α,24‐triol and 3α,7α,11α,24‐tetrol to the corresponding C‐24 carboxylic acids with NaClO₂ catalyzed by 2,2,6,6‐tetramethylpiperidine 1‐oxyl free radical (TEMPO) and NaClO. In summary, 3α,11α‐dihydroxy‐5β‐cholan‐24‐oic acid and 3α,7α,11α‐trihydroxy‐5β‐cholan‐24‐oic acid have been synthesized and their nuclear magnetic resonance (NMR) spectra characterized. These compounds are now available as reference standards to be used in biliary bile acid analysis.     

Oxidative Stress Mediates the Disruption of Airway Epithelial Tight Junctions through a TRPM2-PLCγ1-PKCα Signaling Pathway

Oxidative stress has been implicated as an important contributing factor in the pathogenesis of several pulmonary inflammatory diseases. Previous studies have indicated a relationship between oxidative stress and the attenuation of epithelial tight junctions (TJs). In Human Bronchial Epithelial-16 cells (16HBE), we demonstrated the degradation of zonula occludens-1 (ZO-1), and claudin-2 exhibited a great dependence on the activation of the transient receptor potential melastatin (TRPM) 2 channel, phospholipase Cγ1 (PLCγ1) and the protein kinase Cα (PKCα) signaling cascade.     

A mathematical technique for estimating the melting points of triacylglycerols from the component fatty acid melting points

A method of correlating the value of the melting point of triacylglycerol (tag) with the values of the melting points of the three fatty acids constituting the tag as its acyl radicals was studied by applying the least squares method. The method was applied to the sets of values of the melting points of the α, β', and β forms of crystals of tag with saturated acyl radicals comprising decanoyl, lauroyl, myristoyl, palmitoyl, and stearoyl. The value of the melting point of the crystal form of the tag is expressed by prediction equations that comprise the values of the melting points of the three fatty acids above as variables. The best‐fit equation can be fixed by satisfying the criterion of least squares to the prediction equations. The method enables us to estimate the values of the melting points of possible molecular species of tag consisting of the acyl radicals above. The correlation coefficient relevant to the correlation between the values of the melting points of the particular crystal form and the corresponding values of the best‐fit equation is obtained. The more thermodynamically stable the crystal form, the larger is the value of the correlation coefficient.     

A comparative study on the selective hydrogenation of α,β unsaturated aldehyde and ketone to unsaturated alcohols on Au supported catalysts

The hydrogenation of trans,4-phenyl,3-buten,2-one (benzalacetone) and trans,3-phenyl, propenal (cinnamaldehyde) was carried out on Au supported on iron oxides catalysts. Commercial goethite (FeOOH), maghemite (γFe₂O₃) and hematite (αFe₂O₃) were used as supports. The catalytic activity of Au/Fe₂O₃ reference catalyst, supplied by the World Gold Council, was also investigated. Gold catalysts and the parent supports were characterized by BET, X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed desorption of ammonia (NH₃-TPD) and high resolution transmission electron microscopy (HRTEM).Among the catalysts investigated Au supported on FeOOH shows the highest activity and selectivity to UA in the hydrogenation of unsaturated carbonyl compounds whereas Au supported on αFe₂O₃ are the less active and selective catalysts.The catalytic activity and selectivity to unsaturated alcohols (UA) in the hydrogenation of benzalacetone and cinnamaldehyde are less influenced by the morphology of gold particles and are mainly influenced by the nature of the support.A correlation between the reducibility of the catalysts and the activity and selectivity to UA has been found. Increasing the reducibility of the catalysts both the activity and selectivity to UA increase. These results let us to argue that active and selective sites are formed by negative gold particles formed through the electron transfer from the reduced support to the metal.     

The One‐Pot Wittig Reaction: A Facile Synthesis of α,β‐Unsaturated Esters and Nitriles by Using Nanocrystalline Magnesium Oxide

Nanocrystalline magnesium oxide was found to be an effective heterogeneous, solid base catalyst for the one‐pot Wittig reaction to afford α,β‐unsaturated esters and nitriles in excellent yields with high E‐stereoselectivity in the presence of triphenylphosphine under mild conditions.     

Titanium‐Mediated Direct Carbon‐Carbon Double Bond Formation to α‐Trifluoromethyl Acids: A New Contribution to the Knoevenagel Reaction and a High‐Yielding and Stereoselective Synthesis of α‐Trifluoromethylacrylic Acids

An efficient strategy for a high‐yielding and stereoselective synthesis of α‐trifluoromethyl unsaturated carboxylic acids directly from the reactions of 3,3,3‐trifluoropropanoic acid (CF₃CH₂COOH) with various aryl aldehydes in the presence of titanium tetrachloride (TiCl₄) is reported here for the first time, which is a valuable expansion for the classical Knoevenagel reaction. Because these compounds may have potential applications in organic electronics and can be easily converted to the corresponding fluorinated alcohols and amino acids with excellent bioactivity, this route should be a good choice for the preparation of α‐trifluoromethyl‐containing derivatives.     

Deciphering Specificity Determinants for FR900359‐Derived Gqα Inhibitors Based on Computational and Structure–Activity Studies

Direct targeting of intracellular Gα subunits of G protein‐coupled receptors by chemical tools is a challenging task in current pharmacological studies and in the development of novel therapeutic approaches. In this study we analyzed novel FR900359‐based analogs from natural sources, synthetic cyclic peptides, as well as all so‐far known G_qα inhibitors in a comprehensive study to devise a strategy for the elucidation of characteristics that determine interactions with and inhibition of G_q in the specific FR/YM‐binding pocket. Using 2D NMR spectroscopy and molecular docking we identified unique features in the macrocyclic structures responsible for binding to the target protein correlating with inhibitory activity. While all novel compounds were devoid of effects on G_i and G_s proteins, no inhibitor surpassed the biological activity of FR. This raises the question of whether depsipeptides such as FR already represent valuable chemical tools for specific inhibition of G_q and, at the same time, are suitable natural lead structures for the development of novel compounds to target Gα subunits other than G_q.     

Influence of surface modification on the dispersion of nanoscale α‐Al2O3 particles in a thermoplastic polyurethane matrix

In this study, two types of nanoscale α‐Al₂O₃ particles were used for preparation of α‐Al₂O₃/thermoplastic polyurethane (TPU) composites. These α‐Al₂O₃ particles were either coated or uncoated with stearic acid. For the uncoated α‐Al₂O₃/TPU composite, the results of field‐emission scanning electron microscopy (FE‐SEM) and energy dispersive X‐ray spectrometry indicate that uncoated α‐Al₂O₃ particles are significantly aggregated together. This aggregation is due to the poor compatibility between the inorganic filler (α‐Al₂O₃) and the organic matrix (TPU). The size of clusters is in the range from 5 to 20 μm. For the coated α‐Al₂O₃/TPU composite, FE‐SEM results indicate that most coated α‐Al₂O₃ particles are well dispersed in the TPU matrix. This phenomenon results from the effect of surface modifier (i.e., stearic acid) on α‐Al₂O₃ particles. Stearic acid can act as a compatibilizer to bridge the boundary between the TPU matrix and the α‐Al₂O₃ particle. Stearic acid is not only a suitable surface modifier for the nanoscale α‐Al₂O₃ particle, but also a good dispersant for the dispersion of nanoscale α‐Al₂O₃ particles in the TPU matrix. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Vitamin E Conditionally Inhibits Atherosclerosis in ApoE Knockout Mice by Anti‐oxidation and Regulation of Vasculature Gene Expressions

Lipid deposition in artery walls is implied in the pathogenesis of atherosclerosis and imbalance between uptake and efflux of cholesterol favors the deposition. We investigated the effect of vitamin E with the same dose and duration on the different stages of atherosclerosis in Apolipoprotein E knockout (ApoE KO) mice and explored the potential mechanisms. The results showed that the ApoE KO mouse spontaneously develops atherosclerosis in an age‐dependent manner from 14 to 46 weeks on the regular chow. Vitamin E (100 mg/kg) supplementation to ApoE KO mice at 6, 14, and 22 weeks for 8 weeks significantly reduced the atherosclerotic lesion area by 41, 29 and 19 % respectively compared to the age‐matched control mice; however had no significant effect on the lesion when given at 30 and 38 weeks. In addition, vitamin E supplemented at the ages from 6 to 30 weeks decreased the contents of serum oxLDL and TBARS without affecting the TC and TAG contents in serum and liver. Furthermore, vitamin E supplemented at 6, 14 and 22 weeks down‐regulated vasculature mRNA expressions of scavenger receptor CD36 and up‐regulated mRNA expressions of PPARγ, LXRα and ABCA1 which are involved in reverse cholesterol transportation; however had no significant effects on these genes when given at 30 and 38 weeks. In conclusion, vitamin E with same dose and duration inhibits the early but not advanced atherosclerotic lesion in ApoE KO mice by anti‐oxidation and regulation of mRNA expression of genes involved in cholesterol uptake and efflux, which favors the improvement of atherosclerosis.