Search results for "Nuclear magnetic resonance spectroscopy"
showing 10 items of 843 documents
1H 2D-NMR characterization of Ni(II)-substituted azurin fromPseudomonas aeruginosa
1993
1 H two-dimemional NMR experiments on nickel(II)-substituted azurin have been succesfully applied. Despite the short relaxation time of the hyperfine-shifted resonances, the combined use of NOESY and COSY spectra allowed the alignment of 15 resonances belonging to the metal-coordinated residues Gly-45, His-46, His-117 and Met-121. Even in the case of the two broad and furthest downfield resonances, the NOESY spectra were successful in assigning these signals to the β-CH 2 protons of Cys-112. The protons of the non-coordinated residues Met-13, Phe-15 and Trp-48 were also assigned via NOESY, COSY and TOCSY experiments
Three New Medicagenic Acid Saponins from Polygala micranthaGuill. & Perr.
2011
Three new medicagenic acid saponins, micranthosides A–C (1–3), were isolated from the roots of Polygala micranthaGuill. & Perr., along with six known presenegenin saponins. Their structures were elucidated on the basis of extensive 1D- and 2D-NMR experiments (1H, 13C, DEPT, COSY, TOCSY, NOESY, HSQC, and HMBC) and mass spectrometry as 3-O-β-D-glucopyranosylmedicagenic acid 28-[O-β-D-galactopyranosyl-(14)-O-β-D-xylopyranosyl-(14)-O-α-L-rhamnopyranosyl-(12)-β-D-fucopyranosyl] ester (1), 3-O-β-D-glucopyranosylmedicagenic acid 28-[O-6-O-acetyl-β-D-galactopyranosyl-(14)-O-β-D-xylopyranosyl-(14)-O-α-L-rhamnopyranosyl-(12)-β-D-fucopyranosyl] ester (2), and 3-O-{O-β-D-glucopyranosyl-(13)-O-[β-D-gluc…
Über gemischte bindungen in der IV. hauptgruppe
1987
Abstract Reaction of Ph3SnLi with Ph2SiCl2 or Ph2GeCl2 at −78°C in THF yields (Ph3Sn)2SiPh2 (1) and (Ph3Sn)2GePh2 (2). The crystal structure of 1 (R = 0.075) exhibits SnSi distances of 257.2(4) and 257.9(5) pm, an SnSiSn angle of 118.5(2)°, and a central C3SnSiC2SnC3 molecular skeleton with symmetry close to C2. The geminal NMR coupling 2J(119Sn ⋯ 119Sn) in 1, and in a tri-, tetra- and pentastannane series shows a linear correlation to their respective non-bonded d(Sn ⋯ Sn) distances (I(t-Bu2Sn)4I: 20 Hz/496 pm; 1: 724 Hz/443 pm).
Hydroquinone derivatives from the marine-derived fungus Gliomastix sp.
2017
Eight new hydroquinone derivatives, gliomastins A–D (1–4), 9-O-methylgliomastin C (5), acremonin A 1-O-β-D-glucopyranoside (6), gliomastin E 1-O-β-D-glucopyranoside (7), and 6′-O-acetyl-isohomoarbutin (8), together with seven known analogues were isolated from the marine-derived fungus Gliomastix sp. Their structures were elucidated by extensive spectroscopic analysis including 1D and 2D NMR measurements aided by DFT NMR calculations as well as MS data. TDDFT-ECD and OR calculations were performed to determine the absolute configurations of 1 and the aglycones of 6 and 7. Compound 1 features a novel skeleton, biogenetically derived from a Diels–Alder reaction between derivatives of 11 and 1…
New bioactive alkaloids from the marine sponge Stylissa sp.
2012
Abstract Chemical investigation of the Indonesian marine sponge Stylissa species, which was collected at 2008 from Derawan Islands, Berau, NE Kalimantan, Indonesia offered four new brominated alkaloids, including 12-N-methyl stevensine (1), 12-N-methyl-2-debromostevensine (2), 3-debromolatonduine B methyl ester (3), 3-debromolatonduine A (4) together with eight known alkaloids identified as Z-hymenialdisine, Z-debromohymenialdisine, Stevensine, 2-debromostevensine, 3-bromoaldizine, 3,4-dibromopyrrole-2-carbamide, latonduine A, and latonduine B methyl ester (5–12), respectively. The structures of all isolated compounds were unambiguously elucidated based on extensive 1D and 2D NMR spectrosco…
Expanding the chemical diversity of an endophytic fungus Bulgaria inquinans, an ascomycete associated with mistletoe, through an OSMAC approach
2019
An endophytic fungus Bulgaria inquinans (isolate MSp3-1), isolated from mistletoe (Viscum album), was subjected to fermentation on solid Czapek medium. Chromatographic workup of the crude EtOAc extract yielded five new natural products (1–5). Subsequent application of the “One Strain, MAny Compounds” (OSMAC) strategy on this strain by the addition of a mixture of salts (MgSO4, NaNO3 and NaCl) to solid Czapek medium induced the accumulation of nine additional new secondary metabolites (6–13, 16), with most of them (8, 10–12) not detectable in cultures lacking the salt mixture. The structures of the new compounds were established on the basis of the 1D/2D NMR and HRESIMS data. The TDDFT-ECD m…
Polyketides and nitrogenous metabolites from the endophytic fungus Phomopsis sp. D15a2a
2019
Abstract Three new polyketides, phomopones A−C (1–3), one new cyclic tetrapeptide, 18-hydroxydihydrotentoxin (4), and a new amide, 6-hydroxyenamidin (5) together with a known derivative, enamindin (6) were obtained from the endophytic fungus Phomopsis sp. D15a2a isolated from the plant Alternanthera bettzickiana. The structures of the new compounds were elucidated by 1D, 2D NMR and HRMS data. The absolute configurations of the isolated metabolites were determined either by X-ray crystallography, Marfey’s method or by converting the compounds to Mosher esters.
Two new diterpenoids from kencur (Kaempferia galanga): Structure elucidation and chemosystematic significance
2021
Abstract Aromatic ginger or kencur (Kaempferia galanga L.) rhizomes are ground as a spice or pickled for consumption in south-east Asian cuisines; although widely used, until recently it has been less studied chemically than white and red ginger. Hydro-distillate extracts have identified several compounds that exhibit anticancer activity against select tumor cell lines in vitro, and most recently chemical analyses have focused on rhizome metabolites present in organic extracts. Here we report on two new diterpenoids including Δ8(14),15 polyhydroxlated isopimardienes, 1α-hydroperoxy-2α,6,7-trihydroxy-isopimara-6(7),8(14),15-triene (kaemgalangol E; 1) and 1α,7β-hydroxy-isopimara-8(14),15-dien…
Conformational investigation of αβ-dehydropeptides
2009
Solution conformations of three series of model peptides, homochiral Ac-Pro-L-Xaa-NHCH3 and heterochiral Ac-Pro-D-Xaa-NHCH3 (Xaa = Val, Phe, Leu, Abu, Ala) as well as alpha,beta-unsaturated Ac-Pro-delta Xaa-NHCH3 [delta Xaa = delta Val, (Z)-delta Phe, (Z)-delta Leu, (Z)-delta Abu] were investigated in CDCl3 and CH2Cl2 by 1H-, 13C-NMR, and FTIR spectroscopy. NH stretching absorption spectra, solvent shifts delta delta for NH (Xaa) and NHCH3 on going from CDCl3 to (CD3)2SO, diagnostic interresidue proton NOEs, and trans-cis isomer ratios were examined. These studies performed showed the essential difference in conformational propensities between homochiral peptides (L-Xaa) on the one hand and…
Gold-Catalyzed Suzuki Coupling of ortho -Substituted Hindered Aryl Substrates
2017
International audience; A method that allows hindered ortho-substituted aryl iodides to be efficiently coupled to phenylboronic acid using a gold-catalyzed C-C bond formation is presented. The use of a molecularly-defined dinuclear gold chloride catalytic precursor that is stabilized by a new tetradentate (N,N')-diamino-(P,P')-diphosphino ferrocene hybrid ligand in a Suzuki-type reaction is described for the first time. Electron-rich isopropyl groups on phosphorus were found essen-tial for a superior activity, while the performances of a set of analogous gold dinuclear complexes that were fully characterized by multinuclear NMR spectroscopy and XRD analysis, were investigated. Therefore, ar…