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Ganapaty S.,Gandhi Institute of Technology and Management | Nair V.,University of Gottingen | Devi D.R.,Andhra University | Pannakal S.T.,Andhra University | And 2 more authors.
Natural Product Communications | Year: 2014

Chemical re-examination of the roots of T. calophylla led to the isolation of four isoflavones, namely 2′,4′,5-trihydroxy-6,7-(2″, 2″-dimethylchromene)-8-γ,γ-dimethylallylisoflavone (1a, auriculatin), 2′,5-dihydroxy-6,7-(2″,2″-dimethylchromene)- 4′-γ,γ-dimethylallyloxyisoflavone (2a, isoauriculatin), 3′,4′,5-trihydroxy-6,7-(2″,2″-dimethylchromene) -8-γ,γ-dimethylallylisoflavone (1b, auriculasin), and 3′,5-dihydroxy-6,7-(2″,2″-dimethylchromene)-4′-γ, γ-dimethylallyloxyisoflavone (2b, isoauriculasin). Auriculasin and isoauriculasin are reported for the first time with full NMR assignments. All metabolites were fully characterized by 1D and 2D NMR techniques including COSY, HSQC, HMBC experiments, mass spectra and in part on the basis of X-ray diffraction. Accurate 'invariom' refinements with aspherical scattering factors were carried out for 1a, 1b and 2a.

Kenla T.J.N.,University of Gottingen | Tatong M.D.K.,University of Gottingen | Talontsi F.M.,University of Gottingen | Dittrich B.,Institute for Inorganic and Applied Chemistry | And 2 more authors.
Chemical Communications | Year: 2013

Si-enterobactin (2a), a hexacoordinated complex of the siderophore enterobactin (2b) with silicon as the central atom, was isolated from an endophytic Streptomyces sp. occurring in Piper guinensis roots. The structure and absolute configuration were determined from NMR and MS data, and by X-ray diffraction. The orientation of the molecule along the pseudo-3-fold axis shows that the coordination environment of the silicon atom complexed with three bidentate ligands is Δ. We assume that 2a or related complexes may be involved in the transport of silicon in plants, diatoms, or other silicon-dependent organisms. This journal is © The Royal Society of Chemistry.

Mouafo Talontsi F.,University of Gottingen | Kongue Tatong M.D.,University of Gottingen | Dittrich B.,Institute for Inorganic and Applied Chemistry | Douanla-Meli C.,University of Kassel | Laatsch H.,University of Gottingen
Tetrahedron | Year: 2013

Three α-pyrone derivatives, campyrones A-C (1-3), were isolated from Aspergillus niger, an endophytic fungus occurring in Zanthoxylum lemairei leaves. Their structures were elucidated by detailed spectroscopic and spectrometric analyses and confirmed by X-ray diffraction. The absolute configurations were assigned by a combination of circular dichroism (CD) spectra and X-ray analyses. Biosynthetically, pyrophen (4) and the new derivatives may be derived in a mixed biosynthesis from l-phenylalanine (for 4), l-isoleucine (for 1), l-leucine (for 2), and l-valine (for 3) as starter units, respectively. In bioassays, the new compounds exhibited weak toxicity on brine shrimp larvae (Artemia salina). © 2013 Elsevier Ltd. All rights reserved.

Buchert M.,Institute for Inorganic and Applied Chemistry | Steenbock T.,Institute for Inorganic and Applied Chemistry | Lukaschek C.,Institute for Inorganic and Applied Chemistry | Wolff M.C.,Institute for Inorganic and Applied Chemistry | And 2 more authors.
Chemistry - A European Journal | Year: 2014

Parallel alignment of dipolar electron-donor-p-bridge-electron-acceptor entities can strongly enhance their nonlinear optical properties. This favorable arrangement can be in principle achieved by linking these units covalently or through metal coordination. Four dipolar single-strand chro-mophores decorated with a 5-electron-donor-5′-electron-ac-ceptor-modified 2,2′-bipyridine functionality were synthesized. For two of these chromophores triple-stranded dendritic structures were successfully formed. All of the compounds were characterized with respect to their linear and nonlinear optical properties. For the aldehyde derivatives an enhancement of the first hyperpolarizability of 4.5 rather than 3 was obtained when going from single to triple strands. Theoretical calculations with density functional theory suggest that interstrand transitions contribute to the optical properties of the dendritic structures. © 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

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