Facile one-pot synthesis of sugar-quinoline derivatives

Seven different sugar-quinoline derivatives were synthesised in a ‘one-pot’ reaction from their corresponding C-β-glycoside derivatives. The compounds were characterised by NMR spectroscopy and elemental analysis.     

Regioselective facile one-pot Friedländer synthesis of sugar-based heterocyclic biomolecules

Regioselective facile one-pot synthesis of 16 different sugar-based quinoline, naphthyridine, and xanthone derivatives is reported. The compounds are characterized by NMR spectroscopy and elemental analysis. The β-Anomeric form of the sugar moiety was identified from ¹H NMR studies. Antimicrobial studies of these sugar-heterocyclic derivatives, 3a, 3b, 3f, 5c, 7a, 7b, and 7c show excellent activity against different microbes.     

Further sesquiterpene lactones from the genus Dittrichia

The aerial parts of Dittrichia graveolens afforded in addition to compounds isolated previously five new sesquiterpene lactones, two benzoic acid derivatives while D. viscosa gave two further derivatives of costic acid. The structures were elucidated by high field NMR spectroscopy.     

Preparation and characterization of hemicellulosic derivatives containing carbamoylethyl and carboxyethyl groups

A series of novel water-soluble hemicellulosic derivatives, containing carbamoylethyl and carboxyethyl groups, were heterogeneously synthesized from wheat-straw hemicelluloses with acrylamide (AA) under alkaline conditions. The factors such as reaction temperature, reaction time, molar ratio of catalysis to xylose unit in hemicelluloses and molar ratio of acrylamide to xylose unit in hemicelluloses, were investigated. The average degree of substitution (DS) was calculated by ¹H NMR spectroscopy. DS values up to 0.23 in a one-step synthesis of hemicelluloses derivatives were obtained. Under optimum conditions (60 °C, NaOH to xylose unit in hemicelluloses molar ratio of 0.8, AA to xylose unit in hemicelluloses molar ratio of 8.0, reaction time of 1 h) an expected ratio of carbamoylethyl group to carboxyethyl group of 4.8 in the hemicellulosic derivatives was obtained. The structural features of the hemicellulosic derivatives were characterized by FTIR, NMR spectroscopy, and by elemental analysis. The current work provides a facile method for the synthesis of hemicellulose derivatives with bifunctional groups, which could be used as wet-end additives in the papermaking industry.     

Phloroglucinol derivatives and other constituents from South African Helichrysum species

The investigation of 11 South African Helichrysum species afforded in addition to known compounds 26 further phloroglucinol derivatives, nine diterpenes, a derivative of isocomene and an α-pyrone derivative. The structures were elucidated by highfield NMR spectroscopy and a few chemical transformations. Furthermore the structures of several phloroglucinol derivatives were established by synthesis. The chemotaxonomy is discussed.     

Investigation of the inclusion behavior of chlorogenic acid with hydroxypropyl-β-cyclodextrin

The inclusion complexation behavior of chlorogenic acid (CGA) with the hydroxypropyl-β-cyclodextrin (HP-β-CD) was investigated in both solution and the solid state by UV-vis and fluorescence spectroscopy, infrared spectroscopy (IR), NMR spectroscopy as well as differential scanning calorimetry (DSC). The experimental results indicate that CGA is able to form an inclusion complex with HP-β-CD. The inclusion complex has a stoichiometry of 1:1 and the formation constant was calculated to be 155.7 M⁻¹. The antioxidant activity of CGA on complexation with HP-β-CD increased as compared to uncomplexed CGA. NMR spectroscopic studies show that the aromatic ring and the vinyl group of CGA are deeply included inside the CD cavity.     

Humulene derivatives from Heterotheca villosa

The aerial parts of Heterotheca villosa afforded, in addition to known compounds, eleven new humulene derivatives. The roots gave a new umbelliferone derivative. The structures were elucidated by high-field NMR spectroscopy.     

Structure and chain conformation of five water-soluble derivatives of a beta-D-glucan isolated from Ganoderma lucidum

A linear water-insoluble (1-->3)-beta-D-glucan, coded as GL-IV-I, was isolated from the fruit body of Ganoderma lucidum by extracting with NaOH solution. Its derivatives were prepared by using sulfation, carboxymethylation, hydroxyethylation, hydroxypropylation, and methylation, respectively, and these were labeled as S-GL, CM-GL, HE-GL, HP-GL and M-GL. Five derivatives exhibited good water solubility. Their structures and chain conformations were investigated with infrared spectroscopy, elemental analysis (EA), one- and two-dimensional NMR spectroscopy, laser light scattering (LLS), and size-exclusion chromatography combined with LLS (SEC-LLS). The reactivity of the hydroxyl group of GL-IV-I was ordered as C-6>C-4>C-2 for the five derivatives. The degree of substitution (DS) of the derivatives was calculated from EA and NMR spectroscopy to be from 0.32 to 1.18. The weight-average molecular mass (M(w)) of GL-IV-I, S-GL, CM-GL, HE-GL, HP-GL, and M-GL was 13.3 x 10(4), 10.1 x 10(4), 6.3 x 10(4), 7.2 x 10(4), 5.1 x 10(4), and 14.1 x 10(4), respectively. The conformation analysis studies revealed that GL-IV-I exists as a compact coil in dimethyl sulfoxide, whereas the five derivatives are slightly expanded flexible chains in 0.9% aqueous NaCl solution.     

Bacterial synthesis,purification, and solubilization of membrane protein KCNE3, a regulator of voltage-gated potassium channels

An efficient method is described for production of membrane protein KCNE3 and its isotope labeled derivatives (¹⁵N-, ¹⁵N-/¹³C-) in amounts sufficient for structural-functional investigations. The purified protein preparation within different detergent micelles was characterized using dynamic light scattering, CD spectroscopy, and NMR spectroscopy. It is shown that within DPC/LDAO micelles the protein is in monomeric form and acquires mainly α-helical conformation. The existence of cross-peaks for all glycines of the ¹⁵N-HSQC NMR spectra as well as relatively small line widths (∼20 Hz) confirm the high quality of the preparation and the possibility of obtaining structural-dynamic information on KCNE3 by high resolution heteronuclear NMR spectroscopy.     

Unexpected rearrangement of enantiomerically pure 3-aminoquinuclidine as a simple way of preparing diastereomeric octahydropyrrolo[2,3-c]pyridine derivatives

Reaction of (S)- or (R)-3-aminoquinuclidine with 2-chloropyrimidine or 2-bromopyrimidine led to an unexpected formation of both cis- and trans-octahydropyrrolo [2,3]pyridine derivatives. A single-step synthesis of two of the four stereoisomers of these octahydropyrrolo[2,3]pyridine derivatives provides a convenient way of generating stereochemically defined isomers. Optimization of reaction conditions was carried out by (1)H NMR monitoring. The relative and absolute stereochemistry of all four stereoisomers was determined by a combination of (1)H, (13)C, and (15)N NMR spectroscopy and vibrational circular dichroism spectroscopy.     

α-Isocedrene derivatives, 5-methyl coumarins and other constituents from the subtribe nassauviinae of the compositae

The investigation of four further representatives of the subtribe Nassauviinae afforded in addition to known compounds 17 α-isocedrene derivatives, four methyl coumarins, three methylchromones, three 1βH-guaiene derivatives and three nerolidol derivatives. The structures were elucidated by highfield NMR spectroscopy. The chemotaxonomy of the subtribe Nassauviinae is discussed briefly.     

Four oplopanone and bisabolone derivatives from Rugelia nudicaulis

Rugelia nudicaulis afforded, in addition to known compounds, three new highly oxygenated oplopanone derivatives and a bisabolone derivative. The structures were elucidated by high field ¹H NMR spectroscopy. The chemotaxonomic situation is discussed briefly.     

Chemical modification of bovine pancreatic trypsin inhibitor for single site coupling of immunogenic peptides for NMR conformational analysis

Procedures for chemical modification of bovine pancreatic trypsin inhibitor (BPTI) to allow site-specific coupling of immunogenic peptides are reported. Each of the modified proteins has a single free amino group; the other amino groups of lysine or the amino terminus are blocked by acetylation or guanidination. Two of the derivatives were prepared by protecting Lys-15 by complexation with trypsin or chymotrypsin during acetylation with N-hydroxysuccinimide acetate or guanidination with 3,5-dimethylpyrazole-1-carboxamidine nitrate. A third derivative with a free amino group at the amino terminus was prepared by guanidination of the 4 lysine residues with o-methylisourea. The purity and structural integrity of the modified proteins was checked by NMR spectroscopy. Cysteine-containing peptides can be coupled to the single free amino group using several heterobifunctional linking reagents. N-Succinimidyl 3-(2-pyridyldithio)propionate is the most satisfactory coupling reagent for NMR studies because of its high specificity. Two-dimensional NMR spectroscopy shows that the conformation of the modified proteins is almost identical with that of native BPTI. The BPTI derivatives are suitable for use as models for NMR investigations of the conformation of immunogenic peptides conjugated to a carrier protein.     

Preparation and characterization of cationic corn starch with a high degree of substitution in dioxane-THF-water media

Cationic corn starch derivatives with a high degree of substitution are prepared in alkaline solution or in mixed media of organic solvent and water with different levels of the cationic reagent, 2,3-epoxypropyltrimethylammonium chloride. The starch cationization yield is investigated, and the results indicate that the degree of substitution (DS) of the samples depends on the reaction conditions and reaction media. The maximum DS values are up to 1.37 in 1,4-dioxane alkaline-aqueous solution. Meanwhile, the structures of the cationic starch derivatives are characterized by elemental analyses, FTIR spectroscopy, X-ray diffraction, and ¹³C NMR spectroscopy, as well as by SEM techniques.     

Sesquiterpene lactones and eudesmane derivatives from Onopordon carmanicum

The aerial parts of Onopordon carmanicum afforded in addition to onopordopicrin and two related esters the epoxide of onopordopicrin, a new elemane derivative, two eudesmanolides and two eudesmane derivatives which most likely are the precursors of the latter lactones. The structures were elucidated by highfield NMR spectroscopy.     

Triterpenoids of Cnidosculus urens

The ethanol extract of Cnidosculus urens yielded β-amyrin cinnamate and germanicol acetate. Also, using ¹³C NMR spectroscopy, mixtures of β-amyrin, germanicol and lupeol as well as their acetates were identified.     

Sesquiterpene lactones and other constituents from Tanacetum parthenium

A reinvestigation of the aerial parts of Tanacetum parthenium afforded in addition to known compounds three pinene derivatives, two spiroketal enol ether polyines, four germacranolides; and six guaianolides, two of them being endoperoxides, and two secoguaianolides. The structures were elucidated by high field ¹H NMR spectroscopy, mass spectroscopy and a few chemical transformations. The biogenetic relationships are discussed briefly.     

Synthesis of dinitrophenyl derivatives of 3-O-fatty acyl esters of serine and threonine

The synthesis of 2,4-dinitrophenyl derivatives of the 3-O-oleoyl and 3-O-palmitoyl esters of serine and threonine are described. The derivatives were purified by preparative thin-layer chromatography (TLC) and characterized by 1H-nuclear magnetic resonance (NMR) spectroscopy. These derivatives may be useful for researchers interested in characterizing covalently bound fatty acids on serine and threonine hydroxyl groups of cellular proteins.     

NMR assignments for glucosylated and galactosylated N-acetylhexosaminitols: oligosaccharide alditols related to O-linked glycans from the protozoan parasite Trypanosoma cruzi

We report full 1H and 13C NMR assignments for 13 gluco- or galacto-pyranosylated derivatives of GlcNAc-ol, GalNAc-ol or ManNAc-ol, many of which have been prepared by enzymatic methods. These spectra are reference data to aid the structural analysis by NMR spectroscopy of glycosylated alditols derived from the mucin of the protozoan parasite Trypanosoma cruzi. A series of structural reporter groups for the derivatives from this unusual series of O-glycans are described.     

Structure elucidation and sulfated derivatives preparation of two alpha-D-glucans from Gastrodia elata Bl. and their anti-dengue virus bioactivities

The structures of two glucans, WGEW and AGEW, isolated from Gastrodia elata Bl. were elucidated using monosaccharide composition analysis by gas chromatography (GC), methylation analysis by gas chromatography-mass spectrometry (GC-MS) and nuclear magnetic resonance (NMR) spectroscopy. Their structures were deduced as an alpha-D-(1-->4)-glucan with an alpha-(1-->4) linked branch attached to O-6 branch points with different branch degrees. Their sulfate derivatives with distinct degrees of substitution (DS) were prepared. The substitution position was assigned to O-6 according to the (13)C NMR spectra. All sulfated derivatives showed strong anti-dengue virus bioactivities. The structure-activity relationships (SAR) between the polysaccharides and their sulfated derivatives were also investigated. Results showed that the higher the DS is, the more potent the impact on the dengue virus infection would be.