Borane-pyridine Complex Research Articles

Characterization of a novel + 70 Da modification in rhGM-CSF expressed in E. coli using chemical assays in combination with mass spectrometry

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a cytokine and a white blood cell growth factor that has found usage as a therapeutic protein. During analysis of different fermentation batches of GM-CSF recombinantly expressed in E. coli, a covalent modification was identified on the protein by intact mass spectrometry. The modification gave a mass shift of + 70 Da and peptide mapping analysis demonstrated that it located to the protein N-terminus and lysine side chains. The chemical composition of C4H6O was found to be the best candidate by peptide fragmentation using tandem mass spectrometry. The modification likely contains a carbonyl group, since the mass of the modification increased by 2 Da by reduction with borane pyridine complex and it reacted with 2,4-dinitrophenylhydrazine. On the basis of chemical and tandem mass spectrometry fragmentation behavior, the modification could be attributed to crotonaldehyde, a reactive compound formed during lipid peroxidation. A low recorded oxygen pressure in the reactor during protein expression could be linked to the formation of this compound. This study shows the importance of maintaining full control over all reaction parameters during recombinant protein production.

Modification of lipase from Candida cylindracea with dextran using the borane-pyridine complex to improve organic solvent stability

In this study, a commercial lipase derived from Candida cylindracea was chemically modified with dextran by conjugating ε-amine in the lysine residue with the carbonyl residue in oxidized dextran using the borane-pyridine complex as a reducing agent to increase the hydrophilicity of the microenvironment around the lipase in the presence of organic solvents. The degree of modification (53.2%), amount of dextran (0.66 g/g-lipase), specific activity (similar to that of the unmodified lipase), and stability in the presence of ethanol and 2-propanol (the half-lives were 2.24 and 1.86 times longer than those of the unmodified lipase) were higher for the lipase modified at pH 8.0 than for the lipases modified at other pH levels. Following modification with dextran at pH 8.0, the stability of the modified lipase was higher than that of the unmodified lipase in the presence of 25% (v/v) DMSO, ethanol, 2-propanol, toluene, n-hexane, and isooctane (the half-lives were 1.45, 2.24, 1.86, 1.76, 2.67 and 2.95 times longer than those of the unmodified lipase). Therefore, chemical modification with polysaccharides such as dextran using the borane-pyridine complex as a reducing agent could be a promising approach for improving the organic solvent stability of enzymes.

Graphitized boron-doped carbon foams: Performance as anodes in lithium-ion batteries

The electrochemical performance as potential anodes in lithium-ion batteries of several boron-doped and non-doped graphitic foams with different degree of structural order was investigated by galvanostatic cycling. The boron-doped foams were prepared by the co-pyrolysis of a coal and two boron sources (boron oxide and a borane–pyridine complex), followed by heat treatment in the 2400–2800°C temperature interval. The extent of the graphitization process of the carbon foams depends on boron concentration and source. Because of the catalytic effect of boron, lightweight graphite-like foams were prepared. Boron in the foams was found to be present as carbide (B4C), in substitutional positions in the carbon lattice (B–C), bonded to nitrogen (B–N) and forming clusters. Larger reversible lithium storage capacities with values up to ∼310mAhg−1 were achieved by using the boron oxide-based carbon foams. Moreover, since the electrochemical anodic performance of these boron-doped foams with different degree of structural order is similar, the beneficial effect of the presence of the B–C boron phase was inferred. However, the bonding of boron with nitrogen in the pyridine borane-based has a negative effect on lithium intercalation.

ChemInform Abstract: Synthesis of N-((3-Substituted Phenoxy)alkyl)acetohydroxamic Acids, Potential Inhibitors of the Enzyme 5-Lipoxygenase.

The synthesis of the title compounds starts from methyl (3-subst. phenoxy)alkanoates II which are reduced to the corresponding aldehydes and then transformed to oximes V by reaction with hydroxylamine. Reduction with borane-pyridine complex gives the hydroxylamines VI which on diacetylation and partial deacetylation provide the hydroxamic acids VIII .

Hydrogen adsorption on KOH activated carbons from mesophase pitch containing Si, B, Ti or Fe

Different activated carbons with large micropore volume (0.78–0.99 cm 3/g) have been prepared by KOH activation of mesophase pitch obtained by co-pyrolysis of a petroleum residue and small amounts of different compounds, triphenylsilane, borane pyridine complex, tetrabutyl orthotitanate or ferrocene. During the preparation, the Ti introduced in the petroleum residue concentrate into the activated carbon, whereas some loss of Si and Fe occurs. The compounds modify the size of mesophase structure formed during the co-pyrolysis process, as well as the apparent height of lamelae stack, L c , both having an important effect in the development of the porosity of the activated carbon. However, there is a scarce influence of all heteroatoms in the adsorption capacity of H 2 at −196 °C and at 25 °C, which seems to be mainly influenced by the volume and size of micropores of the activated carbon. Only the activated carbon containing Fe adsorbs a higher amount of hydrogen at 25 °C and 10 MPa than the expected one according to its micropore volume.

Preparation of N-Alkyl-S,S-diphenylsulfimides by the Reaction of N-Unsubstituted S,S-Diphenylsulfimide with Borane-Pyridine

The reaction of an N-unsubstituted S, S-diphenyl-sulfimide with aldehydes or ketones in the presence of a borane-pyridine complex and acetic acid in benzene at 40 °C affords the corresponding N-alkyl- S, S-diphenylsulfimides. Since this reaction does not form the N,N-dialkylated aminosulfonium salt, this method provides a convenient preparation of N-monoalkylsulfimides without the necessity for a difficult separation of the products by column chromatography due to their similar R f values. The mechanism of formation is discussed.

Improved thermal stability and activity in the cold-adapted lipase B from Candida antarctica following chemical modification with oxidized polysaccharides

In order to improve the thermal stability (t(1/2)) and activity of lipase B from cold-adapted Candida antarctica (CALB), amino groups of the enzyme were chemically linked to a range of oxidized polysaccharides using a range of reducing agents. By chemically modifying CALB using 0.1% dextran (250 kDa) at pH 8.6 for 10 days using borane-pyridine complex as reducing agent, increased thermal stability (t(1/2), 168 min at 70 degrees C) and activity (65% higher specific activity) was achieved compared to the unmodified enzyme (t(1/2), 18 min at 70 degrees C). Improvements in thermostability were generally better with high molecular weight polymers such as dextran (40 and 250 kDa) or ficoll (70 and 400 kDa) in comparison to low molecular weight inulin (5 kDa). The shape of the polymer also appeared to be important with elongated, elipsoidal-shaped dextran providing better thermostabilization than spherical-shaped ficoll. Borane-pyridine complex was found to be a good, non-toxic reducing agent for improving thermostability, compared with sodium borohydride and sodium cyanoborohydride. An interesting finding was that, in all cases, specific activity of the modified enzymes increased with a concomitant increase in thermostability. This response defies the general principle of a trade-off between activity and stability, and demonstrates that chemical modification provides new avenues for improving the thermal stability of enzymes from psychrophiles without sacrificing their activity.

Lithium insertion into boron containing carbons prepared by co-pyrolysis of coal–tar pitch and borane–pyridine complex

Carbon materials of boron content ranging from 0.6 to 4 wt.% were synthesized by co-pyrolysis of QI-free coal–tar pitch with the borane–pyridine complex. The growing amount of boron introduced into the carbonaceous material is associated with an increase in nitrogen content and a progressive degradation of structural and textural ordering. The structural variations of the boron-doped materials on heat treatment up to 2500 °C were monitored using X-ray diffraction and X-ray photoelectron spectroscopy. The intrinsic boron acts effectively as a catalyst of graphitization above 2100 °C. The carbonaceous material with boron content of about 1.5 wt% shows the highest degree of structural ordering after thermal treatment. A high amount of oxygen was found in the graphitized boronated carbons, proving that the incorporated boron induces a strong chemisorption activity of the material when exposed to air. For a series of cokes calcined at 1000 °C, the most striking effect of increasing the boron content is an increase of irreversible capacity X irr from 0.2 to 0.7. The reversible capacity ( X rev) amounts to about 1, with a slight tendency to decrease with the boron content. Upon increasing the temperature up to 2500 °C, X irr decreases to about 0.1 in the graphitic carbons, while X rev reaches a minimum of 0.4–0.5 at 1700 °C and next increases to a value close to 1 at 2500 °C. In the boron doped graphite, X irr has a slight tendency to increase with the boron content, due to the simultaneous presence of nitrogen in these materials and their strong affinity for oxygen from the atmosphere.

Effects of borane–pyridine complex on the mesophase pitch formation from decant oil

Mesophase pitches were prepared by adding 0.5 to 2 wt.% of a borane–pyridine complex to a decant oil in a tubing bomb reactor and heating in a fluidized-sand bath held at 500 °C for 30, 45, and 60 min, respectively. The mesophase pitches were analyzed using thermal gravimetric analysis, X-ray diffraction and polarized-light microscopy. Growth and coalescence of mesophase spheres were hindered, while the crystallinity of mesophase pitches was increased when the materials were heat treated with the boron compound. The addition of the borane–pyridine complex also accelerated the coke formation.

A novel solid-phase reductive alkylation route to acridine and dansyl polyamine conjugates

Solid-phase organic synthesis (SPOS) routes to target unsymmetrical polyamines and their acridinyl and dansyl conjugates have been developed based upon borane–pyridine complex (BAP) mediated reductive alkylation, azide reduction with triphenylphosphine, and the use of pent-4-enoyl (Pnt) as an orthogonal amine protecting group.

Solid phase reductive alkylation of secondary amines

Solid phase reductive alkylation of secondary amines has been carried out in excellent yields using borane-pyridine complex (BAP). Various aldehydes and ketones have been reacted with L-proline substituted on high-capacity Wang Resin.

Reductive Amination of Piperidines with Aldehydes Using Borane-Pyridine

Abstract Borane-pyridine complex (BAP) was found to be an excellent replacement for NaCNBH3 in the Borch reduction. Assorted aromatic, heterocyclic and aliphatic aldehydes were reacted with various substituted piperidines using standardized conditions.

Studies on Organophosphorus Compounds; LXXV: A Facile Synthesis of 1-(Hydroxyamino)alkyl(or aryl)phosphonic Acids

Reduction of dialkyl 1-(hydroxyimino)alkyl(aryl)phosphonate 1 with borane-pyridine complex proceeds smoothly to give dialkyl 1-(hydroxyamino) alkyl(or aryl)phosphonate 2 which is then easily converted into the corresponding hydroxyaminophosphonic acid 3 by acidic hydrolysis.

Synthesis of N-[(3-substituted phenoxy)alkyl]acetohydroxamic acids, potential inhibitors of the enzyme 5-lipoxygenase

The synthesis of the title compounds starts from methyl (3-subst. phenoxy)alkanoates II which are reduced to the corresponding aldehydes and then transformed to oximes V by reaction with hydroxylamine. Reduction with borane-pyridine complex gives the hydroxylamines VI which on diacetylation and partial deacetylation provide the hydroxamic acids VIII.

New chemiluminescent derivatizing agent for the analysis of aldehydes and ketones by high-performance liquid chromatography with peroxyoxalate chemiluminescence

Three methods of reductive amination have been investigated for the derivatization of aldehydes and ketones with a new chemiluminescent agent, 3-aminofluoranthene. Use of a borane-pyridine complex was found to give the highest product yield. Analytes were separated by high-performance liquid chromatography (HPLC) and detected by peroxyoxalate chemiluminescence. Detection limits were in the fmol range, chemiluminescence detectability being thirty times better than fluorescence.

スルガトキシン合成に関するモデル実験(第6報)スルガトキシンに対応するエチルエステル誘導体とその立体異性体の合成 その1

Dehydrated surugatoxin ethyl ester analogue 14 was prepared from bromo-nitroketone 11. Alkaline hydrolysis [2% MeONa-MeOH, tetrahydrofuran (THF), room temperature] of 14 gave an enamine derivative 15 which was treated with OsO4 in THF to give a mixture of cis-diols 16α and 16β. Selective reduction of 16α with borane-pyridine complex in AcOH followed by debenzylation of the resulting monool 17 with 90% trifluoroacetic acid at 50°C for 15 min afforded a desired surugatoxin derivative 18. The structure and stereochemistry of 18 was unequivocally determined in a single crystal X-ray diffraction analysis.

The preparation of 1-benzoyl-6,7-dimethoxy-5-keto-1,2,2a,3,4,5-hexahydrobenz[cd]indole

The synthesis of 1 - benzoyl - 6,7 - dimethoxy - 5 - keto - 1,2,2a,3,4,5 - hexahydrobenz[cd]indole ( 10) is described. Reduction of the pyrrole ring of 3 - (5',6' - dimethoxy - 3' - indolyl)propanoic acid ( 6) with borane pyridine complex and a proton source, followed by N-benzoylation furnished the corresponding indoline derivative 3 - (1' -benzoyl - 5', 6' - dimethoxy - 3' - indolinyl)propanoic acid (7). This acid was cyclized with PPA to the target tricyclic ketone ( 10).