Diisopropylethylamine Research Articles

Silver nanoparticle in hyperbranched polyamine: Synthesis, characterization and antibacterial activity

Abstract Silver nanoparticles have been prepared in a hyperbranched polyamine matrix by using a reductive technique. The hyperbranched polyamine has been synthesized by an A2 + B3 approach using 2,4,6-trichloro-1,3,5-triazine and 4,4′-(4,4′-isopropylidene diphenyl-1,1′-diyldioxy) dianiline in the presence of diisopropyl ethyl amine as an active base. The synthesized hyperbranched polyamine and silver nanoparticles were characterized by different spectroscopic and analytical techniques such as FT-IR, UV–vis, 1H NMR, 13C NMR, elemental analysis, solution viscosity, X-ray diffraction, TEM, etc. UV–vis and TEM studies confirm the formation of well-dispersed nanoparticles with average size of 7.2 nm. The thermal behavior of pure polymer and polymer with silver nanoparticles has been studied by thermogravimetric (TG) analysis and differential scanning calorimetric (DSC) studies. These studies indicate the enhancement of thermostability of 40 °C and an increment of 34 °C in glass transition temperature (Tg) of polyamine with silver nanoparticles compared to pure polyamine. The antibacterial activity of silver nanoparticles was tested against Bacillus subtilis and Staphylococcus aureus bacteria at different concentrations by using the diffusion disc technique. The result shows that the antibacterial activity increases with the increase of concentration of the active agent.

The Synthesis of N-TBS-S-Alkynyl Sulfoximines

Treatment of β-keto sulfoximines with triflic anhydride and Hunig's base in toluene resulted in the formation of S-alkynyl sulfoximines in good yield.

Equimolar “a2 + b4” polycondensations—Cyclic polyethers derived from 1,4‐dicyanotetrafluorobenzene and various diphenols

AbstractDicyanotetrafluorobenzene was polycondensed with bisphenol‐P, bisphenol‐M, or 1,4‐bis(4‐hydroxyphenoxy)butane in DMF. Either K2CO3 and ethyldiisopropylamine (EDPA) or tetramethyl piperidine (TMPD) was used as catalysts and HF acceptors. Regardless of base and concentration, all polycondensations of bisphenol‐P or 1,4‐bis(4‐hydroxyphenoxy)butane yielded more or less crosslinked polyethers. In the case of bisphenol‐M, all polycondensations conducted with K2CO3 and 0.4, 0.2, or 0.1 M monomer concentrations resulted again in gelation. Gels were also obtained when polycondensations of 0.4 M monomer solutions were catalyzed with EDPA or TMPD. Yet, at a concentration of 0.2 M, the amines yielded completely soluble polyethers, which were characterized by elemental analyses, inherent viscosities, MALDI‐TOF mass spectrometry, and DSC measurements. The mass spectra revealed that the soluble polyethers mainly consisted of cycles containing two CF bonds per repeat unit. Nearly quantitative substitution of the CF groups with 4‐chlorothiophenol, 4‐bromophenol, 4‐aminophenol, and 4‐phenyl azophenol proved successful, so that a broad variety of multifunctional polyethers was obtained, but in the case of 4‐chloro thiophenol cleavage of the polyether chain also occurred. © 2007 Wiley Periodicals, Inc. JPolym Sci Part A: Polym Chem 46: 543–551, 2008

2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate as an efficient coupling reagent for the amidation and phenylhydrazation of carboxylic acids at room temperature

The synthesis of amides and phenylhydrazides from the reaction of corresponding carboxylic acids with primary aliphatic, aromatic amines or phenylhydrazine in the presence of triethylamine or diisopropylethyl amine as a base using 2-(1H-benzotriazole-1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate (TBTU) proceeds smoothly under mild conditions to afford the corresponding amides or phenylhydrazides in good to high yields in ethyl acetate at room temperature.

Identification of Novel Autoxidation Products of the ω-3 Fatty Acid Eicosapentaenoic Acid in Vitro and in Vivo

Increased intake of fish oil rich in the omega-3 fatty acids eicosapentaenoic acid (EPA, C20:5 omega-3) and docosahexaenoic acid (DHA, C22:6 omega-3) reduces the incidence of human disorders such as atherosclerotic cardiovascular disease. However, mechanisms that contribute to the beneficial effects of fish oil consumption are poorly understood. Mounting evidence suggests that oxidation products of EPA and DHA may be responsible, at least in part, for these benefits. Previously, we have defined the free radical-induced oxidation of arachidonic acid in vitro and in vivo and have proposed a unified mechanism for its peroxidation. We hypothesize that the oxidation of EPA can be rationally defined but would be predicted to be significantly more complex than arachidonate because of the fact that EPA contains an addition carbon-carbon double bond. Herein, we present, for the first time, a unified mechanism for the peroxidation of EPA. Novel oxidation products were identified employing state-of-the-art mass spectrometric techniques including Ag(+) coordination ionspray and atmospheric pressure chemical ionization mass spectrometry. Predicted compounds detected both in vitro and in vivo included monocylic peroxides, serial cyclic peroxides, bicyclic endoperoxides, and dioxolane-endoperoxides. Systematic study of the peroxidation of EPA provides the basis to examine the role of specific oxidation products as mediators of the biological effects of fish oil.

Hyperbranched aromatic polyamines with s‐triazine rings

AbstractTwo aromatic hyperbranched polyamines with s‐triazine rings were synthesized from A2 (4,4′‐sulfonyl dianiline or 4,4′‐methylene dianiline) and B3 (2,4,6‐trichloro‐s‐triazine) types of monomers by a single‐step nucleophilic displacement polymerization technique in the presence of diisopropyl ethyl amine as the base. The hyperbranched polyamines were obtained in high yields (∼ 82–90%) with this technique. The polymers were characterized through solubility testing, measurements of the inherent viscosity, Fourier transform infrared, ultraviolet, 1H‐NMR, and 13C‐NMR spectroscopy, and X‐ray diffraction studies. The inherent viscosities of the polymers were in the range of 0.23–0.42 dL/g in 0.5% (w/v) N,N′‐dimethylacetamide at 27 ± 0.1°C. They were soluble only in highly polar solvents such as N,N′‐dimethylacetamide, dimethylformamide, dimethyl sulfoxide, and N‐methylpyrrolidone. The thermal behavior of the polymers was investigated with thermogravimetric analysis and differential scanning calorimetry studies. The flame‐retardant characteristics of the polymers were tested through the measurement of the limiting oxygen index. In the thermogravimetric analysis of these hyperbranched polyamines, no weight loss was observed below 250°C under a nitrogen atmosphere, whereas differential scanning calorimetry showed that the glass‐transition temperatures were about 240 and 230°C for the polymers with sulfonyl and methylene groups, respectively. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Neuronal Apoptotic Signaling Pathways Probed and Intervened by Synthetically and Modularly Modified (SMM) Chemokines

As the main coreceptors for human immunodeficiency virus type 1 (HIV-1) entry, CXCR4 and CCR5 play important roles in HIV-associated dementia (HAD). HIV-1 glycoprotein gp120 contributes to HAD by causing neuronal damage and death, either directly by triggering apoptotic pathways or indirectly by stimulating glial cells to release neurotoxins. Here, to understand the mechanism of CXCR4 or CCR5 signaling in neuronal apoptosis associated with HAD, we have applied synthetically and modularly modified (SMM)-chemokine analogs derived from natural stromal cell-derived factor-1alpha or viral macrophage inflammatory protein-II as chemical probes of the mechanism(s) whereby these SMM-chemokines prevent or promote neuronal apoptosis. We show that inherently neurotoxic natural ligands of CXCR4, such as stromal cell-derived factor-1alpha or viral macrophage inflammatory protein-II, can be modified to protect neurons from apoptosis induced by CXCR4-preferring gp120(IIIB), and that the inhibition of CCR5 by antagonist SMM-chemokines, unlike neuroprotective CCR5 natural ligands, leads to neurotoxicity by activating a p38 mitogen-activated protein kinase (MAPK)-dependent pathway. Furthermore, we discover distinct signaling pathways activated by different chemokine ligands that are either natural agonists or synthetic antagonists, thus demonstrating a chemical biology strategy of using chemically engineered inhibitors of chemokine receptors to study the signaling mechanism of neuronal apoptosis and survival.

One‐Pot Synthesis of Cyclic Enecarbamates from Lactam Carbamates.

AbstractFor Abstract see ChemInform Abstract in Full Text.

The Direct Catalytic Enantioselective Synthesis of Protected Aryl β‐Hydroxy‐α‐Amino Acids.

AbstractFor Abstract see ChemInform Abstract in Full Text.

One-pot synthesis of cyclic enecarbamates from lactam carbamates

A general, practical and efficient one-pot synthesis of cyclic enecarbamates is described. The protocol proceeds via reduction of lactam carbamate with Super-Hydride ®, followed by in situ dehydration with trifluoroacetic anhydride (TFAA) and diisopropylethylamine (DIPEA).

Synthesis and Fungicidal Activity of Some 6‐Aryl‐2‐(β‐D‐glucopyranosyl)‐3‐oxo‐2,3‐dihydro‐1,3,4‐oxadiazolo [3,2‐b]‐1,2,4,6‐thiatriazine‐1,1‐dioxides.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Design of a Novel Class of Peptide Inhibitors of Cyclin-dependent Kinase/Cyclin Activation

Cyclin dependent kinases (CDKs) are key regulators of the cell cycle progression and therefore constitute excellent targets for the design of anticancer agents. Most of the inhibitors identified to date inhibit kinase activity by interfering with the ATP-binding site of CDKs. We recently proposed that the protein/protein interface and conformational changes required in the molecular mechanism of CDK2-cyclin A activation were potential targets for the design of specific inhibitors of cell cycle progression. To this aim, we have designed and characterized a small peptide, termed C4, derived from amino acids 285-306 in the alpha5 helix of cyclin A. We demonstrate that this peptide does not interfere with complex formation but forms stable complexes with CDK2-cyclin A. The C4 peptide significantly inhibits kinase activity of complexes harboring CDK2 in a competitive fashion with respect to substrates but does not behave as an ATP antagonist. Moreover, when coupled with the protein transduction domain of Tat, the C4 peptide blocks the proliferation of tumor cell lines, thereby constituting a potent lead for the development of specific CDK-cyclin inhibitors.

Alkynylation of N‐Tosylimines with Aryl Acetylenes Promoted by ZnBr2 and N,N‐Diisopropylethylamine in Acetonitrile.

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New total synthesis of the marine antitumor alkaloid (-)-agelastatin A.

[reaction: see text] A new total synthesis of (-)-agelastatin A (1) has been achieved from the chiral oxazolidinone (-)-3. Although enone transposition was problematic when the Michael ring closure of 2 was attempted with strong base, the desired cyclization could be effected with Hunig's base after the pyrrole nucleus was brominated. Subsequent reduction and monobromination afforded synthetic (-)-agelastatin A (1).

Cyclofunctionalization of Unsaturated Alcohols, Phenols, Acids, and Sulfonamides with 1‐Benzenesulfinyl Piperidine and Trifluoromethanesulfonic Anhydride.

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Cyclofunctionalization of Unsaturated Alcohols, Phenols, Acids, and Sulfonamides with 1-Benzenesulfinyl Piperidine and Trifluoromethanesulfonic Anhydride

The combination of a benzenesulfinamide, trifluoromethanesulfonic anhydride, and Hunig's base brings about the cyclofunctionalization of unsaturated alcohols, phenols, acids, and sulfonamides to give the corresponding α-phenylsulfanylmethyl cyclic ethers, lactones and sulfonamides, respectively. In an unanticipated twist the products are isolated at the sulfur (II) oxidation state denoting an overall reduction in the oxidation state of the sulfur based electrophile in the course of the reaction.

Modular Synthesis of Amine‐Functionalized Oxazolines.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Polymers of carbonic acid 32: Influence of catalysts on propagation and cyclization in the interfacial polycondensation of bisphenol A with diphosgene

AbstractBisphenol A was polycondensed with diphosgene in a dichloromethane/aqueous NaOH system. Temperature, time, and molar ratios of the reactants were optimized according to a previously elaborated optimization of the hydrolytic polycondensation of bisphenol A bischloroformate. Five of the following catalysts were examined: triethylamine, 4‐(N,N‐dimethylamino)pyridine (DMAP), ethyldiisopropylamine (EDPA), tetrabutylammonium hydrogen sulfate, and triethylbenzylammonium chloride (TEBA‐Cl). Triethylamine and DMAP accelerated the hydrolysis of diphosgene by formation of a hydrophilic acylammonium salt. Therefore, the molecular weights decreased with higher concentration of these tert‐amines. However, the molecular weights increased (weight‐average molecular weight up to 106) with higher concentrations of tetraalkylammonium salts because these catalysts favor chain growth in the organic phase via “naked” phenoxide ions without catalyzing the hydrolysis of diphosgene. EDPA gave poor results under all circumstances. Cyclic polycarbonates were discovered in all samples. Their fraction increased with the average molecular weight of the samples. When samples prepared with triethylamine or TEBA‐Cl were fractionated, cycles having molar masses up to 15,000 Da were detected by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectroscopy. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 890–904, 2003

Nα-Urocanylhistamine: A Natural Histamine Derivative

Nα-Urocanylhistamine and two related compounds were synthesized by using PyBOP coupling protocols. These compounds represent naturally occurring histamine derivatives.

The Fluorous Swern and Corey—Kim Reactions: Scope and Mechanism.

AbstractFor Abstract see ChemInform Abstract in Full Text.