Search results for "two-dimensional"

Lactones from the Sponge-Derived Fungus Talaromyces rugulosus.

2017

The marine-derived fungus Talaromyces rugulosus isolated from the Mediterranean sponge Axinella cannabina and cultured on solid rice medium yielded seventeen lactone derivatives including five butenolides (1–5), seven (3S)-resorcylide derivatives (6–12), two butenolide-resorcylide dimers (13 and 14), and three dihydroisocoumarins (15–17). Among them, fourteen compounds (1–3, 6–16) are new natural products. The structures of the isolated compounds were elucidated by 1D and 2D NMR (Nuclear Magnetic Resonance) spectroscopy as well as by ESI-HRMS (ElectroSpray Ionization-High Resolution Mass Spectrometry). TDDFT-ECD (Time-Dependent Density Functional Theory-Electronic Circular Dichroism) calcul…

Kaemgalangol A: Unusual seco-isopimarane diterpenoid from aromatic ginger Kaempferia galanga.

2018

Abstract A new unusual seco-isopimarane, kaemgalangol A (1) and 12 usual analogs (2−13) were isolated from the rhizomes of Kaempferia galanga (Family: Zingiberaceae). KaemgalangolA (1) represented a rarely isolated 9,10-seco-isopimarane skeleton. The chemical structures of the isolated compounds were mainlyinvestigated by spectroscopic techniques such as 1D, 2D NMR, and HRMS. The absolute configuration of 1–3 was studied by X-ray diffraction analysis as well as experimental and TDDFT-calculated electronic circular dichroism. Among the isolated diterpenoids, 5, 6 and 9 exhibited cytotoxic activity against HeLa (IC50 75.1, 74.2 and 76.5 μM, respectively) and HSC-2 (IC50 69.9, 53.3 and 58.2 μM…

Ancistrolikokine I and further 5,8'-coupled naphthylisoquinoline alkaloids from the Congolese liana Ancistrocladus likoko and their cytotoxic activit…

2018

Abstract The Congolese liana Ancistrocladus likoko (Ancistrocladaceae) produces naphthylisoquinoline alkaloids that are, chemotaxonomically remarkable, all based on the same coupling type, with the biaryl axis located between C-5 and C-8′. About 20 alkaloids, belonging to the subclass of 5,8′-linked naphthylisoquinolines, have so far been discovered in this plant species. Here, we report on the isolation and structure elucidation of six further such 5,8′-coupled monomeric alkaloids, named ancistrolikokines I (9), C3 (10), F2 (11), J (12), J2 (13), and J3 (14). They were identified in the twigs of A. likoko, along with the two new atropo-diastereomeric dimers michellamines A8 (15a) and B8 (1…

Ancistectorine D, a naphthylisoquinoline alkaloid with antiprotozoal and antileukemic activities, and further 5,8'- and 7,1'-linked metabolites from …

2016

From the twigs and stems of the Chinese liana Ancistrocladus tectorius (Ancistrocladaceae), two new 5,8'-coupled naphthylisoquinolines, ancistectorine D (5) and its 6-O-demethyl derivative 6, were isolated, along with two new 7,1'-linked alkaloids, 6-O-methylancistectorine B1 (7) and ancistectorine B2 (8). Two further compounds, ancistroealaine A (4) and 6-O-demethyl-8-O-methyl-7-epi-ancistrobrevine D (10), already known from related Asian and African Ancistrocladus species, were discovered for the first time in A. tectorius. The structure elucidation was achieved by spectroscopic analysis including HRESIMS, 1D and 2D NMR, and by chemical (oxidative degradation) and chiroptical (circular di…

Cytotoxic secondary metabolites from the endophytic fungus Aspergillus versicolor KU258497

2018

Abstract Two new isocoumarin dimers (1 and 2) and one new dihydroquinolone derivative (3) were isolated from Aspergillus versicolor, an endophyte derived from leaves of the Egyptian water hyacinth Eichhornia crassipes (Pontederiaceae), together with ten other known metabolites. Chemical structures of the isolated metabolites were determined based on HRESIMS, extensive 1D and 2D NMR spectroscopy. The relative and absolute configurations of the new natural products were established by ROESY and electronic circular dichroism (ECD) spectroscopy, respectively. The axial chirality of the isocoumarin 7,7′-homodimers (1 and 2) was deduced by TDDFT-ECD calculations. All isolated compounds were asses…

New Austalides from the Sponge-Associated Fungus Aspergillus sp.

2011

Chromatographic separation of a crude extract obtained from the fungus Aspergillus sp., isolated from the Mediterranean sponge Tethya aurantium, yielded five new meroterpenoid metabolites, austalides M–Q (1–5), together with nine known compounds (6–13). The structures of the new compounds were unambiguously elucidated on the basis of extensive 1D and 2D NMR methods and by mass spectral analysis. Furthermore, the absolute configurations of 1 and 4 were determined by time-dependent density functional theory electronic circular dichroism (TDDFT ECD) calculations, allowing the assignment of the absolute configuration of analogous compounds 2, 3, and 5. The calculations revealed that the conform…

2019

A unique series of six biaryl natural products displaying four different coupling types (5,1′, 7,1′, 7,8′, and 5,8′) were isolated from the roots of the West African liana Ancistrocladus abbreviatus (Ancistrocladaceae). Although at first sight structurally diverse, these secondary metabolites all have in common that they belong to the rare group of naphthylisoquinoline alkaloids with a fully dehydrogenated isoquinoline portion. Among the African Ancistrocladus species, A. abbreviatus is so far only the second one that was found to produce compounds with such a molecular entity. Here, we report on four new representatives, named ancistrobreveines A–D (12–14, and 6). They were identified alon…

Filtering design for two-dimensional Markovian jump systems with state-delays and deficient mode information

2014

This paper is concerned with the problem of H"~ filtering for a class of two-dimensional Markovian jump linear systems described by the Fornasini-Marchesini local state-space model. The systems under consideration are subject to state-delays and deficient mode information in the Markov chain. The description of deficient mode information is comprehensive that simultaneously includes the exactly known, partially unknown and uncertain transition probabilities. By invoking the properties of the transition probability matrix, together with the convexification of uncertain domains, a new H"~ performance analysis criterion for the filtering error system is firstly derived. Then, via some matrix i…

Model approximation for two-dimensional Markovian jump systems with state-delays and imperfect mode information

2014

Published version of an article in the journal: Multidimensional Systems and Signal Processing. Also available from the publisher at: http://dx.doi.org/10.1007/s11045-013-0276-x This paper is concerned with the problem of {Mathematical expression} model approximation for a class of two-dimensional (2-D) discrete-time Markovian jump linear systems with state-delays and imperfect mode information. The 2-D system is described by the well-known Fornasini-Marchesini local state-space model, and the imperfect mode information in the Markov chain simultaneously involves the exactly known, partially unknown and uncertain transition probabilities. By using the characteristics of the transition proba…

In-situ monitoring by Raman spectroscopy of the thermal doping of graphene and MoS2 in O-2-controlled atmosphere

2017

The effects of temperature and atmosphere (air and O2) on the doping of monolayers of graphene (Gr) on SiO2 and Si substrates, and on the doping of MoS2 multilayer flakes transferred on the same substrates have been investigated. The investigations were carried out by in situ micro-Raman spectroscopy during thermal treatments up to 430 °C, and by atomic force microscopy (AFM). The spectral positions of the G and 2D Raman bands of Gr undergo only minor changes during treatment, while their amplitude and full width at half maximum (FWHM) vary as a function of the temperature and the used atmosphere. The thermal treatments in oxygen atmosphere show, in addition to a thermal effect, an effect a…