scholarly journals Three New Spongian Diterpenes from the Fijian Marine Sponge Spongia sp

2009 ◽  
Vol 4 (3) ◽  
pp. 1934578X0900400 ◽  
Author(s):  
Harald Gross ◽  
Anthony D. Wright ◽  
Uwe Reinscheid ◽  
Gabriele M. König
Keyword(s):  
Molecular Modeling ◽  
Marine Sponge ◽  
Spectroscopic Data ◽  
Chemical Investigation ◽  
Complete Analysis ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
Fiji Islands ◽  
Combined Strategy ◽  
Spongian Diterpene

Chemical investigation of the marine sponge Spongia sp., collected from the Fiji Islands resulted in the isolation of three new furanoditerpenoids 1-3, along with the known compounds epispongiatriol (4) and 17,19-dihydroxyspongia-13(16),14-dien-2,3-dione (5) While 1 is a new spongian diterpene with a modified oxidation pattern, compounds 2 and 3 represent two new ring A-contracted spongians, displaying a novel and unprecedented nor-spongian carbon skeleton. Despite their labile nature the structures could be established through a combined strategy including complete analysis of spectroscopic data (NMR, MS), molecular modeling and quantum-mechanical calculations.

scholarly journals Plakilactones G and H from a marine sponge. Stereochemical determination of highly flexible systems by quantitative NMR-derived interproton distances combined with quantum mechanical calculations of 13C chemical shifts

2013 ◽  
Vol 9 ◽  
pp. 2940-2949 ◽  
Author(s):  
Simone Di Micco ◽  
Angela Zampella ◽  
Maria Valeria D’Auria ◽  
Carmen Festa ◽  
Simona De Marino ◽  
...  
Keyword(s):  
Marine Sponge ◽  
Molecular System ◽  
Chemical Shifts ◽  
Integrated Approach ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
Chemical Derivatization ◽  
Fiji Islands ◽  
Interproton Distances

In this paper the stereostructural investigation of two new oxygenated polyketides, plakilactones G and H, isolated from the marine sponge Plakinastrella mamillaris collected at Fiji Islands, is reported. The stereostructural studies began on plakilactone H by applying an integrated approach of the NOE-based protocol and quantum mechanical calculations of 13C chemical shifts. In particular, plakilactone H was used as a template to extend the application of NMR-derived interproton distances to a highly flexible molecular system with simultaneous assignment of four non-contiguous stereocenters. Chemical derivatization and quantum mechanical calculations of 13C on plakilactone G along with a plausible biogenetic interconversion between plakilactone G and plakilactone H allowed us to determine the absolute configuration in this two new oxygenated polyketides.

scholarly journals Saturated Ceramides from the Sponge Dysidea Robusta

2009 ◽  
Vol 4 (7) ◽  
pp. 1934578X0900400
Author(s):  
Suzi O. Marques ◽  
Katyuscya Veloso ◽  
Antonio G. Ferreira ◽  
Eduardo Hajdu ◽  
Solange Peixinho ◽  
...  
Keyword(s):  
Marine Sponge ◽  
Crude Extract ◽  
Spectroscopic Data ◽  
Chemical Investigation ◽  
Ms Analysis

Chemical investigation of the crude extract of a marine sponge Dysidea robusta led to the isolation of an inseparable mixture of saturated ceramides. These were identified from spectroscopic data as well as by hydrolysis followed by LC-MS analysis of the sphingosine moieties.

Vibration Frequencies and Normal Coordinates of Benzo(c)phenanthrene

2001 ◽  
Vol 56 (6-7) ◽  
pp. 499-504
Author(s):  
Rehab M. Kubba ◽  
Muthana Shanshal
Keyword(s):  
Spectroscopic Data ◽  
Normal Coordinate Analysis ◽  
Quantum Mechanical ◽  
Ir Absorption ◽  
Quantum Mechanical Calculations ◽  
Vibration Frequencies ◽  
Normal Coordinate ◽  
Normal Coordinates ◽  
Comparative Relations

Abstract MINDO/3-FORCES quantum mechanical calculations yielded non-planar (C2) geometry of Ben-zo(c)phenanthrene. The result agrees with the majority of published results but disagrees with others in which a planar (C2 V) structure was accepted in order to simplify the analysis of certain spectroscopic data. Vibration frequencies and IR absorption intensities were calculated then, applying the non-planar (C2) structure. A complete normal coordinate analysis for the molecule is reported. Inspection of these coordinates allowed the discovery of some useful comparative relations between them, which are re­ ported in the paper.

Synthesis, isolation and characterization of a stable lithium stannenolate. A keto or an enol tautomer?

2021 ◽  
Vol 50 (39) ◽  
pp. 13651-13655
Author(s):  
Roman Bashkurov ◽  
Natalia Fridman ◽  
Dmitry Bravo-Zhivotovskii ◽  
Yitzhak Apeloig
Keyword(s):  
Spectroscopic Data ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
Isolation And Characterization ◽  
Enol Tautomer

The synthesis and isolation of the first stable lithium stannenolate is reported. Structural and spectroscopic data, in combination with DFT quantum-mechanical calculations, indicate that the stannenolate adopts the keto tautomeric structure.

Crystal Forms of Semisynthetic Ergot Alkaloid Terguride

2002 ◽  
Vol 67 (4) ◽  
pp. 479-489 ◽  
Author(s):  
Michal Hušák ◽  
Bohumil Kratochvíl ◽  
Ivana Císařová ◽  
Ladislav Cvak ◽  
Alexandr Jegorov ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Ergot Alkaloid ◽  
Simplified Model ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
X Ray Diffraction ◽  
Torsion Angles ◽  
Crystal Forms ◽  
X Ray ◽  
Independent Molecules

Two new structures of semisynthetic ergot alkaloid terguride created by unusual number of symmetry-independent molecules were determined by X-ray diffraction methods at 150 K. Form A (monoclinic, P212121, Z = 12) contains three symmetry-independent terguride molecules and two molecules of water in the asymmetric part of the unit cell. The form CA (monoclinic, P21, Z = 8) is an anhydrate remarkable by the presence of four symmetry-independent molecules in the crystal structure. Conformations of twelve symmetry-independent molecules that were found in four already described terguride structures are compared with torsion angles obtained by ab initio quantum-mechanical calculations for the simplified model of N-cyclohexyl-N'-diethylurea.

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