Pseudo-poly(amino acid)s: study on construction and characterization of novel chiral and thermally stable nanostructured poly(ester-imide)s containing different trimellitylimido-amino acid-based diacids and pyromellitoyl-tyrosine-based diol

A new class of chiral and potentially biodegradable poly(ester-imide)s (PEI)s as pseudo-poly(amino acid)s (PAA)s bearing natural amino acids in the main chain was synthesized. In this investigation, N,N′-(pyromellitoyl)-bis-(L-tyrosine dimethyl ester) as a biodegradable optically active diphenol and synthesized trimellitic anhydride-derived dicarboxylic acids containing different natural amino acids such as S-valine, L-methionine, L-leucine, L-isoleucine, and L-phenylalanine were used for direct polyesterification. With the aim of tosyl chloride/pyridine/N,N′-dimethylformamide system as a condensing agent, the new optically active PEIs were obtained in good yields and moderate inherent viscosity up to 0.42 dL/g. The obtained polymers were characterized with FT-IR, ¹H-NMR, X-ray diffraction (XRD), field emission scanning electron microscopy, elemental, and thermogravimetric analysis techniques. These polymers show high solubility in organic solvents, such as N,N′-dimethyl acetamide, N-methyl-2-pyrrolidone, and sulfuric acid at room temperature, and are insoluble in solvents, such as methylene chloride, cyclohexane, and water. Morphology probes showed these pseudo-poly(amino acid)s were noncrystalline and nanostructured polymers. On the basis of thermogravimetric analysis data, such PAAs are thermally stable and can be classified as self-extinguishing polymers. In addition due to the existence of amino acids in the polymer backbones these pseudo-PAAs not only are optically active but also are expected to be biodegradable and therefore could be classified under eco-friendly polymers.     

New optically active and thermally stable poly(ester-imide)s containing bicyclo segment in the main chain: Synthesis and characterization

New optically active diacid containing L-2-aminobutyric acid moiety was prepared by reacting bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride 1, with L-2-aminobutyric acid 2 in the acetic acid, and was polymerized with several aromatic diols 5a–f to obtain a new series of optically active poly(ester-imide)s (PEIs) through direct polycondensation using tosyl chloride/pyridine/N,N-dimethylformamide system as condensation agent. The data obtained by these methods indicate that, good yields and inherent viscosities are resulted. These polymers are readily soluble in polar organic solvents such as N,N-dimethyacetamide, N,N-dimethyformamide, dimethyl sulfoxide. The obtained polymers were characterized by FTIR, specific rotation measurements, elemental analysis and ¹H NMR spectroscopy. The thermal stability of the resulting PEIs were evaluated with thermogravimetric analysis and differential scanning calorimetry techniques under a nitrogen atmosphere.     

Synthesis and characterization of optically active poly(amide-imide)s containing photosensitive chalcone units in the main chain

<正>A series of new optically active poly(amide-imide)s were synthesized by direct polycondensation reaction of 4,4'-diaminochalcone with several N-trimellitylimido-L-amino acids using a tosyl chloride(TsCl),pyridine(Py) and dimethylformamide(DMF) system as condensing agent.The resulting thermally stable poly(amide-imide)s were obtained in good to high yields and inherent viscosities ranging between 0.35 dL/g and 0.58 dL/g and were characterized with FTIR, ~1H-NMR,CHN,Ultraviolet,TGA and DTG techniques.     

Synthesis and characterization of optically active polyamides based on 2-(1,3-isoindolinedione-2-yl)glutaric acid by direct polycondensation

<正>Five new optically active polyamides(PAs) 6a-6e were prepared by direct polycondensation reaction of 2-(1,3- isoindolinedione-2-yl)-glutaric acid 4 as a new chiral diacid with various aromatic diamines 5a-5e in a medium consisting of triphenyl phosphite(TPP),calcium chloride,pyridine(Py) and N-methyl-2-pyrrolidone(NMP).The polycondensation reaction produced a series of polyamids 6a-6e in quantitative yields with inherent viscosities of 0.26-0.39 dL/g.The resulting polymers were fully characterized by means of ~1H-NMR,FT-IR spectroscopy,elemental analysis,inherent viscosity and specific rotation.Thermal properties of these polymers were investigated using thermal gravimetric analysis (TGA) and differential thermal gravimetry(DTG).Phthalimide rings as a bulky pendent group in the polymer chains disturb the interchain and intrachain interactions and make these PAs readily soluble in polar,aprotic solvents such as N,N-dimethyl acetamide(DMAc),N,N-dimethyl formamide(DMF),dimethyl sulfoxide(DMSO),N-methyl-2-pyrrolidone(NMP) and sulfuric acid.     

Diisocyanate route as a convenient method for the preparation of novel optically active poly(amide-imide)s based on N-trimellitylimido-S-valine

A new class of optically active poly(amide-imide)s based on an α-amino acid was synthesized via direct polycondensation reaction of different diisocyanates with a chiral diacid monomer. The step-growth polymerization reactions of N-trimellitylimido-S-valine (TISV) (1) with 4,4′-methylene-bis(4-phenylisocyanate) (MDI) (2) was performed under microwave irradiation, as well as solution polymerization under graduate heating and reflux conditions. The optimized polymerization conditions for each method were performed with tolylene-2,4-diisocyanate (TDI) (3), hexamethylene diisocyanate (HDI) (4), and isophorone diisocyanate (IPDI) (5) to produce optically active poly(amide-imide)s via diisocyanate route. The resulting polymers have inherent viscosities in the range of 0.02-1.10 dL/g. Decomposition temperatures for 5% weight loss (T₅) occurred above 300 °C (by TGA) in nitrogen atmospheres. These polymers are optically active, thermally stable and soluble in amide-type solvents. Some structural characterization and physical properties of this new optically active poly(amide-imide)s are reported.     

Synthesis and characterization of optically active poly(amide-imide)s based on [N,N′-(4,4′-carbonyldiphtaloyl)-bis-lamino diacid]s and 1,5-bis(4-aminophenyl)penta-1,4-dien-3-one

Six dicarboxylic acids 3a-3f were synthesized by the reaction of 3,3’,4,4’-benzophenonetetracarboxylic dianhydride 1 with L-aminoacids 2a-2f in a solution of glacial acetic acid/pyridine(Py) at refluxing temperature.Then six new poly(amide-imide)s PAIs were synthesized from the direct polycondensation reaction of[N,N’-(4,4’- carbonyldiphtaloyl)-bis-L-amino diacid]s with 1,5-bis(4-aminophenyl)penta-1,4-dien-3-one(APPD).The polymerization reactions produced a series of new optically active PAIs with high yield and good inherent viscosity.Also these PAIs are optically active and soluble in various organic solvents.These resulting new polymers can be used in column chromatography for the separation of enantiomeric mixtures.The resulted polymers were fully characterized by means of FTIR and ~1H-NMR spectroscopy,elemental analyses,inherent viscosity measurements,solubility tests and thermogravimetric analysis(TGA).     

Reaction of syndiotactic poly(methacrylic acid hydrazide) with functional carboxylic acids

As a highly reactive tactic vinyl polymer, syndiotactic poly(methacrylic acid hydrazide) (s-PMH) was prepared from syndiotactic poly(methyl methacrylate) (s-PMMA) by hydrazinolysis. The s-PMH served as the starting polymer to prepare other tactic vinyl homopolymers having optically active functional carboxylic acids or N-protected amino acids as side chains. The condensation of the acids was carried out in water by water-soluble carbodiimides. Conversion was followed by pH and the resulting homopolymers characterized by ¹H- and ^13C-NMR spectroscopy. The NMR-spectra were assigned by comparison with low molecular weight model compounds, derived from pivalic acid hydrazide. In a third on-polymer reaction, the OH-groups present in the side chains of some of the polymers were employed for adding an optically active isocyanate to yield branched side chains.     

Electrochemical studies of sulfonates in non-aqueous solvents: Part III. Trifluoromethanesulfonic acid as a strong acid in dipolar aprotic solvents and acetic acid

Dissociation of trifluoromethanesulfonic acid in non-aqueous solvents has been investigated mainly by conductometry and compared with that of p-toluenesulfonic, methanesulfonic, fluorosulfuric and perchloric acids. The solvents used are dimethyl sulfoxide, N,N-dimethylacetamide, N,N-dimethylformamide, n-butyronitrile, propylene carbonate, acetonitrile, nitromethane, methyl isobutyl ketone and acetic acid. Trifluoromethanesulfonic acid is completely dissociated in rather basic solvents such as dimethyl sulfoxide, dimethylacetamide and dimethylformamide, while it is associated to some extent in the other solvents, especially in methyl isobutyl ketone and acetic acid. The strength of trifluoromethanesulfonic acid is almost the same as that of perchloric acid in all the solvents. Dissociation constants of the other acids are also obtained.     

Solvent effects in the absorption spectra of the Ninhydrin chromophore

Visible spectra of the Ninhydrin chromophore, Ruhemann's purple, were studied in dimethyl sulfoxide (DMSO), formamide, N, N-dimethylformamide (DMF), and pyridine, as well as in mixed aqueous-nonaqueous solvent media. Large differences in both the position of absorption maxima and extinction coefficients for the two bands in the visible spectra in the various solvent media were observed. Both the absorption maxima and the extinction coefficients of the Ninhydrin chromophore were a linear function of the composition of dimethyl sulfoxide-H₂O solvent media. The experimental evidence allows predictions of values for the two absorption maxima of Ruhemann's purple as a function of the nature of the solvent medium. In nonaqueous aprotic solvents (i.e., DMSO and DMF), the maxima should be near 605 and 420 mμ; in nonaqueous aprotic solvents capable of undergoing charge-transfer interactions (i.e., pyridine), near 550 and 420 mμ; and in nonaqueous protic solvents (i.e., formamide), near 575 and 410 mμ. The maxima in aprotic media will be displaced to about 575 mμ (higher wavelength band) and 410 mμ (lower wavelength band) on dilution with protic solvents.     

A 2‐Tyr‐1‐carboxylate Mononuclear Iron Center Forms the Active Site of a Paracoccus Dimethylformamidase

N,N‐dimethyl formamide (DMF) is an extensively used organic solvent but is also a potent pollutant. Certain bacterial species from genera such as Paracoccus, Pseudomonas, and Alcaligenes have evolved to use DMF as a sole carbon and nitrogen source for growth via degradation by a dimethylformamidase (DMFase). We show that DMFase from Paracoccus sp. strain DMF is a halophilic and thermostable enzyme comprising a multimeric complex of the α₂β₂ or (α₂β₂)₂ type. One of the three domains of the large subunit and the small subunit are hitherto undescribed protein folds of unknown evolutionary origin. The active site consists of a mononuclear iron coordinated by two Tyr side‐chain phenolates and one carboxylate from Glu. The Fe³⁺ ion in the active site catalyzes the hydrolytic cleavage of the amide bond in DMF. Kinetic characterization reveals that the enzyme shows cooperativity between subunits, and mutagenesis and structural data provide clues to the catalytic mechanism.     

Design and synthesis of novel organosoluble chiral poly(amide-ether-imide-urea) containing l-leucine moieties in the main chain

N,N′-(pyromellitoyl)-bis{N-[4(4-aminophenoxy)phenyl]-2-(4-methyl)p-entanamide} (5), as a novel chiral diamine, is synthesized through dehydration of l-leucine and pyromellitic dianhydride followed by the treating with thionyl chloride and subsequent reaction with 4,4′-diamino diphenylether in dry tetrahydrofuran. Several novel optically active poly(amide-ether-imide-urea)s (PAEIUs) with inherent viscosities of 0.37–0.46 dL g⁻¹ are synthesized via the polymerization of compound 5 with various diisocyanates under different catalytic conditions. The obtained PAEIUs are characterized by means of FT-IR, ¹H-NMR, elemental analysis, and specific rotation measurement techniques. The new polymers are readily soluble in polar organic solvents such as N,N-dimethyacetamide, N,N-dimethyformamide, and dimethyl sulfoxide, while the evaluation of their thermal stability by thermogravimetric analysis and differential scanning calorimetry confirmed their moderate to good thermal stability. Compared with our previous work, here, we have different functional groups in the main chain which provide novel polymers with much better solubility while maintaining reasonable thermal properties.     

Polymerization of methylmethacrylate with cetyl pyridinium bromide (CPB)-benzoyl peroxide (BZ2O2) combination as a redox initiator and with CPB as a lone photoinitiator

Polymerization of MMA was carried out in near-bulk and in fairly dilute solutions in DMF at 40° with (1) CPB-BZ₂O₂ combination as the redox initiator in the dark and (2) CPB as the sole photoinitiator in visible light. R_p was proportional to ([CPB] [BZ₂O₂])^0.18 for the redox polymerization and to [CPB]^0.35 for the photopolymerization both in near-bulk (10% DMF, v/v) and in high dilution (50% DMF, v/v). Polymerization was inhibited by hydroquinone in each case indicating a radical mechanism. Effect of several solvents/additives on the polymerization revealed that dimethyl formamide, acetonitrile and pyridine acted as rate enhancing solvents in the redox polymerization while in the photopolymerization they acted as normal diluents; benzene, methanol, acetone and chloroform exhibited inert nature while formamide and acetamide behaved as retarding additives in both types of polymerization. Initiator transfer of the degradative type reasonably explains kinetic nonidealities.     

Characterization of N,N‐dimethyl amino acids by electrospray ionization–tandem mass spectrometry

Methylation is an essential metabolic process for a number of critical reactions in the body. Methyl groups are involved in the healthy function of the body life processes, by conducting methylation process involving specific enzymes. In these processes, various amino acids are methylated, and the occurrence of methylated amino acids in nature is diverse. Nowadays, mass‐spectrometric‐based identification of small molecules as biomarkers for diseases is a growing research. Although all dimethyl amino acids are metabolically important molecules, mass spectral data are available only for a few of them in the literature. In this study, we report synthesis and characterization of all dimethyl amino acids, by electrospray ionization–tandem mass spectrometry (MS/MS) experiments on protonated molecules. The MS/MS spectra of all the studied dimethyl amino acids showed preliminary loss of H₂O + CO to form corresponding immonium ions. The other product ions in the spectra are highly characteristic of the methyl groups on the nitrogen and side chain of the amino acids. The amino acids, which are isomeric and isobaric with the studied dimethyl amino acids, gave distinctive MS/MS spectra. The study also included MS/MS analysis of immonium ions of dimethyl amino acids that provide information on side chain structure, and it is further tested to determine the N‐terminal amino acid of the peptides. Copyright © 2015 John Wiley & Sons, Ltd.     

Acylation of Cellulose with N,N′‐Carbonyldiimidazole‐Activated Acids in the Novel Solvent Dimethyl Sulfoxide/Tetrabutylammonium Fluoride

Summary: Carboxylic acids were efficiently activated with N,N′‐carbonyldiimidazole (CDI) and applied for the acylation of cellulose under homogeneous conditions using dimethyl sulfoxide (DMSO)/tetrabutylammonium fluoride trihydrate (TBAF) as solvent. The simple and elegant method is a very mild and easily applicable tool for the synthesis of pure aliphatic, alicyclic, bulky, and unsaturated cellulose esters with degrees of substitution of up to 1.9. Products are soluble in organic solvents, e.g., DMSO or N,N‐dimethylformamide (DMF). The cellulose esters were characterized by elemental analysis, FT‐IR, ¹H and ¹³C NMR spectroscopy and show no impurities or substructures resulting from side reactions.

The esterification of cellulose using carboxylic acids activated in situ with N,N′‐carbonyldiimidazole.     

Palladium-catalyzed intra-molecular olefin insertion reaction of α-alkenyl-α-acyloxytrialkylsilane. Synthesis of optically active carbocycle

Pd-catalyzed intra-molecular olefin insertion/carbonylation reaction of optically active α-alkenyl-α-acyloxysilanes is described. The reactions proceeded in a stereoselective manner to give five- and six-membered optically active carbocycles having (E)-vinylsilane in their side chains. Under CO condition, optically active carbocycles containing one-carbon homologated side chain were produced by Pd-catalyzed tandem olefin insertion-carbonylation reaction.     

Ligand trans-effect in octahedral complexes of 3d metals and its manifestation in the synthesis of metalloporphyrins in solution

We study features of the indicator kinetic reaction of meso(tetraphenyl)tetrabenzoporhine with cobalt(II), nickel(II), and manganese(II) acetates in electron-donating organic solvents (N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and pyridine (Py)) and in their binary mixtures at temperatures in the range 348–368 K. Specific features of the trans-effect of solvent molecules on the rate and activation parameters of formation of manganese(II), cobalt(II), nickel(II), and copper(II) complexes with porphyrin are noted.     

Synthesis and characterization of novel optically active poly(ester‐imide)s with high Tg and good thermal stability

A series of novel optically active poly(ester‐imide)s (ter‐PEIs) with high glass transition temperature (T_g), good thermal stability, and solubility were successfully designed and synthesized by direct polycondensation reactions, using p‐hydroxybenzoic acid (PHB), 4,4’‐dihydroxybenzophenone, and a chiral diacid, N,N'‐(pyromellitoyl)‐bis‐L‐phenylalanine diacid as monomers. The resulting terpolymers were characterized by¹H‐NMR, FTIR, element analysis, thermogravimetric analysis, different scanning calorimeter and wide‐angle x‐ray diffraction, etc. The ter‐PEIs are amorphous polymers with good heat resistance and high T_gs. They are soluble in many common polar organic solvents and show optically rotation property. The specific rotation values of the ter‐PEIs increase with the molar ratio of the chiral diacid, and the rigid PHB monomer is beneficial to increase the T_gs of the polymers. Copyright © 2013 John Wiley & Sons, Ltd.     

Syntheses of stereoregular and optically active polyamides from active 4-chloro-1-benzotriazolyl diesters and diamines

A new route to prepare optically active polyamides was established, based on the polycondensation of two new active diesters: the active diesters of 4-chloro-1 hydroxybenzotriazole, such as 1,1'-(terephthaloyldioxy)bis(4-chloro-benzotriazole), and 1,1'-(isophthaloyldioxy)bis(4-chlorobenzotriazole), with optically active isomers of 2,4-diaminopentane. Dipolar aprotic solvents such as N,N-dimethylformamide and dimethyl sulfoxide were used as reaction solvents. The solution polycondensation carried out in solution at room temperature afforded optically active polyamides. The aminolysis of the two active diesters was carried out as a model reaction study.     

Regioselective intramolecular asymmetric cyclization of symmetrical open chain triketone

The title reactions performed with (S)-α-amino acids or their derivatives as chiral sources were found to regioselectively give enantiomeric pairs of optically active 4-acetyl-3, 4-dimethyl-2-cyclohexenone (R)(+)- and (S)(?)-$\text{4}$), 16–25% e.e., and those of optically active 6-acetyl-3,6-dimethyl-2-cyclohexenone((R)(+)- and (S)(?)-$\text{5}$, 54–59% e.e., from the open chain triketone($\text{3}$).     

Studies on synthesis and in vitro biodegradability of novel optically active nanostructure poly(ester-imide)s containing <Emphasis Type="SmallCaps">l</Emphasis>-phenylalanine and <Emphasis Type="SmallCaps">l</Emphasis>-isoleucine linkages

A series of biodegradable functional amino-acid-based poly(ester-imide)s (PEI)s were designed and synthesized by the direct polycondensation reaction of chiral diacids composed of naturally occurring α-amino acids with 4,4′-thiobis(2-tert-butyl-5-methylphenol) in the presence of tosyl chloride, pyridine, and N,N-dimethylformamide as a condensing agent. These new chiral polymers were characterized with respect to chemical structure and purity using specific rotation experiments, FT-IR, ¹H-NMR, techniques, and elemental analysis. The surface morphology of these polymers was investigated by field emission scanning electron microscopy. The result indicated nanoscale morphology of the obtained polymers. Thermal stability and the weight loss behavior of the resulting PEIs were studied by TGA techniques. All PEIs showed no significant weight loss below 400 °C in a N₂ environment. The monomers and prepared polymers were co-cultivated with airborne fungal spores in culture media to study their biological activity. Soil burial test was also used for evaluation of their biodegradation behavior. The results showed that the synthesized monomers and their derived polymers are biologically active and that their degradation products are probably nontoxic to microbial growth.