Free NH Groups Research Articles

Intramolecular cyclization of acetylene-containing α-amino carboxylates and α-amino phosphonates: synthesis of α-CF3-substituted dehydroprolines and their P-analogs

CF3-Containing α-arylpropargyl-α-amino carboxylates and α-arylpropargyl-α-amino phosphonates on treatment with the Bronsted or Lewis acids undergo cyclization involving the free NH2 group and triple bond to yield the corresponding dehydroprolines and their phosphorus analogs.

INFRARED SPECTRA OF PYRROLES AND DIPYRRYLMETHANES

The IR spectra of 18 substituted pyrroles and 6 substituted dipyrrylmethanes are investigated. It is shown that the position of the valence vibrations frequency of the free NH group, ν free NH depends on the number of substituents in the ring. The frequency is influenced by the electronegativity of a substituent, the effect of an α- being much more marked than that of a β-substituent. The stability of the hydrogen bond increases with increase in substituent electronegativity. When two electronegative substituents occupy the α and β positions, they have a mutually weakening effect. The ν C=O (acetyl) absorption bands in pyrrolecontaining compounds are situated 40–60 cm −1 lower than in aromatic ketones and greatly depend on the position and nature of the substituent in the pyrrole ring. Authors: A. F. Mironov, L. D. Miroshnichenko, R. P. Evstigneeva, N. A. Preobrazhenskii. English Translation in Chemistry of Heterocyclic Compounds , 1965, 1 (1), pp 49-53 http://link.springer.com/article/10.1007/BF01168919

Two-step crystal engineering of porous nets from [Cr3(μ3-O)(RCO2)6] and [Cu3(μ3-Cl)(RNH2)6Cl6] molecular building blocks

Two porous nets have been prepared via a 2-step crystal engineering approach that links decorated trigonal prismatic [Cr3(μ3-O)(CO2)6] and [Cu3(μ3-Cl)(RNH2)6Cl6] molecular building blocks, MBBs. tp-PMBB-5-acs-1 is a rare example of a rigid acs underlying net whereas tp-PMBB-6-stp-1, an stp underlying net, exhibits free NH2 groups in its channels and a relatively high isosteric heat of adsorption for CO2.

Pyrazoles as ligands for the Rh-catalyzed hydroformylation of alkenes in supercritical carbon dioxide

Activity of pyrazole ligands in hydroformylation of a number of unsaturated terminal substrates in supercritical carbon dioxide (scCO2) in the presence of Rh-catalyst was studied. The ligands without free NH group at position 1 of the pyrazole ring were found to be active. The use of scCO2 as the reaction medium served to reach a higher conversion and regioselectivity of hydroformylation as compared to those in toluene.

Direct Pd‐Catalyzed Cross‐Coupling of Functionalized Organoaluminum Reagents

A handsome couple: Through the use of the simple Pd catalyst [Pd(tmpp)(2)Cl(2)] (tmpp = tris(2,4,6-trimethoxyphenyl)phosphine) and THF/DMF as solvent, various aryl-, heteroaryl-, benzyl- and alkylaluminum reagents can be readily cross-coupled with aryl or heteroaryl iodides, bromides, and nonaflates, and in special cases even with chlorides and triflates. This cross-coupling tolerates free NH(2) groups, aldehydes, ketones, esters, and nitro functions.

A general template for synthesis of hollow microsphere with well‐defined structure

AbstractUsing chitooligosaccharides (COS) as the backbones and polycaprolactones (PCL) as the branches, a novel type of amphiphilic graft copolymers with a large amount of free OH and NH2 groups remained on the COS backbones was synthesized. The obtained Chitooligosaccharide‐graft‐poly(ε‐caprolactone)(COS‐g‐PCL) was self‐assembled into giant vesicles which served as templates for the preparation of hollow spheres of a series of metals(Au, Ag, Cu, Pt, and Pd). The method involved the initial mixing of COS‐g‐PCL and metal‐containing groups or metal ions to generate corresponding complex, followed by adding the selective solvent of water to induce the self‐assembly of the graft copolymers into giant vesicles; Metal ions were reduced and crosslinked by a subsequent calcination procedure to form metal hollow spheres. In addition, hybrid hollow spheres with fluorescent quantum dots and silica hollow spheres were also prepared by slightly modified procedures. A preliminary study on the trinitrotoluene sensor of CdS/vesicle hybrid hollow spheres revealed a considerable sensitivity, which exemplifies the distinct properties imparted by the hybrid hollow structure. All of the results demonstrate that the giant vesicles self‐assembled from COS‐g‐PCL could be utilized as effective templates for the synthesis of various hollow spheres. Using Chitooligosaccharide‐graft‐poly(ε‐caprolactone) vesicles as general templates, the hollow spheres of a series of metals such as Au, Ag, Cu, and Pt were produced. The method involved the initial absorption of metal ions from solution into the functional surface layer of the graft copolymer giant vesicles. Metal ions were reduced and crosslinked by a subsequent calcination procedure to form metal hollow spheres. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

ChemInform Abstract: Ruthenium(0)‐Catalyzed sp3 C—H Bond Arylation of Benzylic Amines Using Arylboronates.

AbstractAn efficient arylation adjacent to the free NH group in substrates (I) and (VII) includes pyridine‐directed cyclometalation with Ru3(CO)12.

Preparation and characterization of porous scaffold composite films by blending chitosan and gelatin solutions for skin tissue engineering

AbstractBiodegradable polymers have significant potential in biotechnology and bioengineering. However, for some applications, they are limited by their inferior mechanical properties and unsatisfactory compatibility with cells and tissues. In the present investigation blends of chitosan and gelatin with various compositions were produced as candidate materials for biomedical applications. Fourier transform infrared spectral analysis showed good compatibility between these two biodegradable polymers. The composite films showed improved tensile properties, highly porous structure, antimicrobial activities, low water dissolution, low water uptake and high buffer uptake compared to pure chitosan or gelatin films. These enhanced properties could be explained by the introduction of free OH, NH2 and NHOCOCH3 groups of the amorphous chitosan in the blends and a network structure through electrostatic interactions between the ammonium ions (NH3+) of the chitosan and the carboxylate ions (COO−) of the gelatin. Scanning electron microscopy images of the blend composite films showed homogeneous and smooth surfaces which indicate good miscibility between gelatin and chitosan. The leafy morphologies of the scaffolds indicate a large and homogeneous porous structure, which would cause increased ion diffusion into the gel that could lead to an increase in stability in aqueous solution, buffer and temperature compared to the gelatin/chitosan system. In vivo testing was done in a Wistar rat (Rattus norvegicus) model and the healing efficiencies of the scaffolds containing various compositions of chitosan were measured. The healing efficiencies in Wistar rat of composites with gelatin to chitosan ratios of 10:3 and 10:4 were compared with that of a commercially available scaffold (Eco‐plast). It was observed that, after 5 days of application, the scaffold with a gelatin to chitosan ratio of 10:3 showed 100% healing in the Wistar rat; however, the commercial Eco‐plast showed only a little above 40% healing of the dissected rat wound. Copyright © 2012 Society of Chemical Industry

Effect of aggregation behavior of gelatin in aqueous solution on the grafting density of gelatin modified with glycidol

The effect of aggregation behavior of gelatin in aqueous solution on the grafting density of glycidol grafted gelatin polymers (GGG polymers) was investigated. The grafting density was measured using the Van Slyke method by calculating the conversion rate of free NH2 groups of gelatin. The conversion rate reached peak values at 6% and 14% of the gelatin aqueous solution. SEM micrographs displayed a series of structural transitions (i.e., spherical, spindle, butterfly, irregular and dendritic aggregates) at varying concentrations from 2% to 16% (w/w) at an interval of 2% (w/w). The spindle aggregates reappeared at the concentrations of 6% and 14%. Viscosity measurements indicated that the physicochemical properties of the gelatin solution had changed with increasing concentration. UV and CD analysis indicated that hydrophobic interactions competed with hydrogen bonding, and the random coils partly transformed to β-sheet structure by changing the concentration. Zeta potential and pH data confirmed the increasing electrostatic repulsion associated with increasing the hydrophobic region. XPS analysis revealed that the elemental composition of the gelatin particle surface changed with variation in the aggregate structure, determining the monotonic variation of the grafting density with increasing concentration. Results demonstrate that aggregation behavior of gelatin in aqueous solution plays a crucial role in deciding the grafting density of gelatin modified products.

Synthesis and tuberculostatic activity of novel N′‐methyl‐4‐(pyrrolidin‐1‐yl)picolinohydrazide and N′‐methylpyrimidine‐2‐carbohydrazide derivatives

AbstractThe synthesis of N′‐methyl‐4‐(pyrrolidin‐1‐yl)picolinohydrazide and N′‐methyl‐pyrimidine‐2‐carbohydrazide derivatives (5a and 5b) was carried out. These compounds were used as starting materials to obtain methyl N′‐methylhydrazinecarbodithioates 6a and 6b, which, on reaction with either triethylamine or hydrazine, gave corresponding 1,3,4‐oxadiazioles 7a and 7b or 1,2,4‐triazoles 9a and 9b with the free NH2 group at the N‐4 position, respectively. Compounds 8a–e, particularly containing cyclic amines at N‐4 of the 1,2,4‐triazole ring, were also obtained. Synthesized compounds were tested in vitro for their activity against Mycobacterium tuberculosis. The structure–activity relationship analysis for obtained compounds was done. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:223–230, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.21008

Facile synthesis and basic catalytic application of 3D mesoporous carbon nitride with a controllable bimodal distribution

Here we demonstrate a facile synthesis of 3D mesoporous carbon nitride with Ia3d symmetry (MCN-6) using mesoporous silica KIT-6 with 3D porous structure and different pore diameters as hard templates, and ethylenediamine and carbon tetrachloride as the sources for N and C, and C, respectively. The obtained materials possess bimodal pores that can be controlled with a simple adjustment of the pore diameter of the KIT-6 templates. The lower angle powder X-ray diffraction (XRD) patterns and high resolution transmission electron microscope (HRTEM) images confirm that the MCN-6 materials possess a well-ordered mesoporous 3D structure with a highly interwoven and a branched pore structure. The textural parameters such as the specific surface areas and specific pore volumes of the materials can also be controlled by tuning the pore diameter of the hard template. The specific surface area and the specific pore volume of the samples increase with increasing the pore diameter of the hard template. The C/N ratio of the MCN-6 is ca. 4.3 which is similar to that obtained for MCN-1 prepared from SBA-15 as template. FT-IR and XPS spectroscopy results reveal that samples contain a CN network with a lot of free NH2 groups which are originated from ethylenediamine and can offer the basic sites. The temperature programmed desorption of CO2 confirms that the samples are highly basic and the basicity of the sample is 0.195 mmol of CO2 per g which is higher than that of MCN-1 (0.14 mmol of CO2 per g). We tested the performance of MCN-6 materials in the base-catalyzed Knoevenagel condensation of benzaldehyde and malononitrile. The catalysts exhibit excellent activity and afford a high yield of the corresponding α,β-unsaturated nitrile in a short reaction time even at room temperature. In addition, catalysts are highly stable and can be recyclable several times without affecting their activity.

Pd‐Catalyzed Synthesis of ArSCF3 Compounds under Mild Conditions

Pd‐Catalyzed Synthesis of ArSCF₃ Compounds under Mild Conditions

Synthesis of 3-Aryl-2-arylamidobenzofurans Based on the Curtius Rearrangement

The synthesis of novel 3-aryl-2-arylamidobenzofurans has been accomplished via a Curtius rearrangement strategy in four steps from benzofuran-2-carboxylic acids. The requisite Suzuki-Miyaura cross-coupling, with benzyl 3-bromobenzofuran-2-ylcarbamate or 2-arylamido-3-bromobenzofurans, revealed an unusual reductive debromination process due to the presence of the free NH group. This dehalogenation can be suppressed by N-alkylation. DMAP is an efficient reagent for the one-pot conversion of benzyl benzofuran-2-ylcarbamates into the corresponding benzofuran-2-arylamides through aroylation, thus acting both as an acyl transfer reagent and a deprotecting agent of the Cbz group. A mechanism is postulated.

Design and synthesis of some pyrazole derivatives of expected anti-inflammatory and analgesic activities

Design and synthesis of some pyrazole derivatives 4–11 of expected anti-inflammatory and analgesic activities. In addition, docking of the tested compounds into cyclooxygenase II using (MOE) was performed to rationalize the obtained biological results and their mechanism of action. The structures of the new compounds were elucidated by spectral and elemental analyses. All the newly synthesized compounds were evaluated for their anti-inflammatory activity using the carrageenan-induced rat paw edema method. Analgesic activity of the target compounds was measured using the p-benzoquinone writhing-induced method, and their ability to induce gastric toxicity was also evaluated. Results showed that the newly synthesized compounds exhibited weak to good activities compared to ibuprofen and celecoxib as reference drugs. Some compounds, such 4a and 11b exhibited significant anti-inflammatory activity with gastric ulcerogenic potential less than that of ibuprofen. Results of the analgesic activity showed that compounds possessing good anti-inflammatory activity showed also good analgesic. Substitution of pyrazole ring with at least one aryl moiety was found to be essential for anti-inflammatory and analgesic activities. Free NH (of pyrazole ring) and/or acidic group (COOH) will improve the anti-inflammatory activity.

The R 2 2 (8) Hydrogen-Bonded Supramolecular Synthon in Two Novel Glycoluril Derivatives

Two new glycoluril derivatives, namely 6-phenyl-1,4-dioxo-2,2a,3,4,6,7-hexahydro-1H,5H-2,3,4a,6,7a-pentaazacyclopenta[cd]indene-2a,7b-dicarboxylate (1), and diethyl 6-(2,4-dichorophenyl)-1,4-dioxo-2,2a,3,4,6,7-hexahydro-1H,5H-2,3,4a,6,7a-pentaazacyclopenta[cd]indene-2a,7b-dicarboxylate (2) have been synthesized and structurally determined by X-ray diffraction analysis. Compound 1 is, monoclinic, space group C2/c, with a = 20.0784(7), b = 9.0316(3), c = 23.0980(8) A, β = 98.3930(10), V = 4143.7(2) A3, with Z = 8 for d calc = 1.338 Mg/m3. The analog 2 is, Triclinic, space group P-1, with a = 8.9353(18), b = 10.466(2), c = 14.679(3) A, β = 73.60(3), V = 1268.1(4) A3, with Z = 2 for d calc = 1.533 Mg/m3. X-ray analysis reveals that both glycoluril derivatives bearing two free syn-urea NH groups and two ureidyl C=O, assemble the same one-dimensional chains in the solid-state running parallel to the [110], [1–10] and [010] directions via N–H···O hydrogen bonds. Two new glycoluril derivatives, namely 6-phenyl-1,4-dioxo-2,2a,3,4,6,7-hexahydro-1H,5H-2,3,4a,6,7a-pentaazacyclopenta[cd]indene-2a,7b-dicarboxylate (1), and diethyl 6-(2,4-dichorophenyl)-1,4-dioxo-2,2a,3,4,6,7-hexahydro-1H,5H-2,3,4a,6,7a-pentaazacyclopenta[cd]indene-2a,7b-dicarboxylate (2), both bearing two free syn-urea NH groups and two ureidyl C=O, assemble the same one-dimensional chains in the solid-state running parallel to the [110], [1–10] and [010] directions via R 2 2 (8) N–H···O hydrogen bonds.

Dynamics and Couplings of N−H Stretching Excitations of Guanosine−Cytidine Base Pairs in Solution

N-H stretching vibrations of hydrogen-bonded guanosine-cytidine (G·C) base pairs in chloroform solution are studied with linear and ultrafast nonlinear infrared (IR) spectroscopy. Assignment of the IR-active bands in the linear spectrum is made possible by combining structural information on the hydrogen bonds in G·C base pairs with literature results of density functional theory calculations, and empirical relations connecting frequency shifts and intensity of the IR-active vibrations. A local mode representation of N-H stretching vibrations is adopted, consisting of ν(G)(NH(2))(f) and ν(C)(NH(2))(f) modes for free NH groups of G and C, and of ν(G)(NH(2))(b), ν(G)(NH), and ν(C)(NH(2))(b) modes associated with N-H stretching motions of hydrogen-bonded NH groups. The couplings and relaxation dynamics of the N-H stretching excitations are studied with femtosecond mid-infrared two-dimensional (2D) and pump-probe spectroscopy. The N-H stretching vibrations of the free NH groups of G and C have an average population lifetime of 2.4 ps. Besides a vibrational population lifetime shortening to subpicosecond values observed for the hydrogen-bonded N-H stretching vibrations, the 2D spectra reveal vibrational excitation transfer from the ν(G)(NH(2))(b) mode to the ν(G)(NH) and/or ν(C)(NH(2))(b) modes. The underlying intermode vibrational couplings are on the order of 10 cm(-1).

Molecular Self‐Assembling of N‐Methylacetamide in Solvents

The self‐association of N‐methylacetamide (NMA), which is one of the most simple compound having a peptide bond, in various solvents such as carbon tetrachloride (CCl4), chloroform, dichloromethane, and acetonitrile was studied through the near‐infrared (NIR) spectroscopic observation at various temperatures and concentrations. An analysis assuming a successive association processes for the NMA molecules was applied to the sharp 1470‐nm band (the first‐overtone band of NH stretching vibration mode attributed to free NH group of NMA monomer and partly to the free, terminal NH group of NMA aggregate); the mean association number for NMA in CCl4 increases with increasing concentration and decreases with increasing temperature. Comparisons of the association number of NMA in various solvents indicate that the degree of association is in the following order: CCl4≫ chloroform ≒ dichloromethane > acetonitrile. Interestingly, the association number of NMA in CCl4 is thought to be larger than that in its pure liquid.

Mechanism in Brill transition of polyamide 66 studied by two-dimensional correlation infrared spectroscopy

The Brill transition of polyamide 66 was investigated by temperature-dependent infrared spectroscopy combined with moving-window two-dimensional (MW2D) correlation spectroscopy. The temperature range of the Brill transition determined by MW2D correlation spectroscopy was 90–170 °C. We employed generalized 2D correlation spectroscopy to study the sequential order of polyamide 66 chains with linear increment of temperature. The movement of the methylene segments near to NH is earlier than those on the C O sides. At the same time, the methylene which is close to NH varies before the inner methylene. Three kinds of NH groups in polyamide 66 were found. The sequential order of their motions is as follows. The free hydrogen-bonded NH groups change first, and then the disordered hydrogen-bonded NH groups. Finally, the ordered hydrogen-bonded NH groups start to change. We also found that the changes of the ordered hydrogen-bonded NH groups follow with the methylene groups.

Structure and proton-donor ability of N-(1-trifluoromethylsulfonylamino-2,2,2-trichloroethyl)-acrylamide

Quantum-chemical calculations (B3LYP/6-311G**) of N-(1-trifluoromethylsulfonylamino-2,2,2-trichloroethyl)acrylamide CF3SO2NHCH(CCl3)NHC(O)CH=CH2 (I) in the isolated state revealed four local minima corresponding to the conformers with the syn- and antiperiplanar orientation of the C=O and N-H bonds in the amide fragment, two of which containing the intramolecular C(O)NH…O=S or SO2NH…O=C hydrogen bonds. Judged from the data of IR spectroscopy and dielectrometry, compound I in inert media exists predominantly in the form of conformer with antiperiplanar amide fragment and free NH group. Its self-associates in molecular crystals and solutions are formed by hydrogen bonds SO2NH…O=C. Spectroscopic acidity of compound I determined as the value of Δν(NH) upon interactions with DMF in CCl4 is higher than that of N-methyltrifluoromethanesulfonamide.

Simultaneous quantification of glucosylceramide and galactosylceramide by normal-phase HPLC using O-phtalaldehyde derivatives prepared with sphingolipid ceramide N-deacylase

We report here a method of simultaneously quantifying glucosylceramide (GlcCer) and galactosylceramide (GalCer) by normal-phase HPLC using O-phtalaldehyde derivatives. Treatment with sphingolipid ceramide N-deacylase which converts the cerebrosides in the sample to their lyso-forms was followed by the quantitative labeling of free NH(2) groups of the lyso-cerebrosides with O-phtalaldehyde. Using this method, 14.1 pmol of GlcCer and 10.4 pmol of GalCer, and 108.1 pmol of GlcCer and 191.1 pmol of GalCer were detected in zebrafish embryos and RPMI 1864 cells, respectively, while 22.2 pmol of GlcCer but no GalCer was detected in CHOP cells using cell lysate containing 100 microg of protein. Linearity for the determination of each cerebroside was observed from 50 to 400 microg of protein under the conditions used, which corresponds to approximately 10(3) to 10(5) RPMI cells and 5 to 80 zebrafish embryos. The present method clearly revealed that the treatment of RPMI cells with a GlcCer synthase inhibitor P4 resulted in a marked decrease in GlcCer but not GalCer, concomitantly with a significant decrease in the GlcCer synthase activity. On the other hand, GlcCer but not GalCer increased 2-fold when an acid glucocerebrosidase inhibitor CBE was injected into zebrafish embryos. Interestingly, the treatment of CHOP cells with ciclosporin A increased GlcCer possibly due to the inhibition of LacCer synthase. A significant increase in levels of GlcCer in fibroblasts from patients with Gaucher disease was clearly shown by the method. The proposed method is useful for the determination of GlcCer and GalCer levels in various biological samples.