Quantitative NMR-Derived Interproton Distances Combined with Quantum Mechanical Calculations of 13C Chemical Shifts in the Stereochemical Determination of Conicasterol F, a Nuclear Receptor Ligand from Theonella swinhoei

2012 ◽  
Vol 77 (3) ◽  
pp. 1489-1496 ◽  
Author(s):  
Maria Giovanna Chini ◽  
Catharine R. Jones ◽  
Angela Zampella ◽  
Maria Valeria D’Auria ◽  
Barbara Renga ◽  
...  
Keyword(s):  
Nuclear Receptor ◽  
Chemical Shifts ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
Quantitative Nmr ◽  
Receptor Ligand ◽  
13C Chemical Shifts ◽  
Theonella Swinhoei ◽  
Interproton Distances

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 Oxygenated Theonellastrols: Interpretation of Unusual Chemical Behaviors Using Quantum Mechanical Calculations and Stereochemical Reassignment of 7α-Hydroxytheonellasterol

Marine Drugs ◽  
2020 ◽  
Vol 18 (12) ◽  
pp. 607
Author(s):  
A-Young Shin ◽  
Hyi-Seung Lee ◽  
Yeon-Ju Lee ◽  
Jong Seok Lee ◽  
Arang Son ◽  
...  
Keyword(s):  
Chemical Shift ◽  
Chemical Shifts ◽  
Atomic Orbital ◽  
2D Nmr ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
Epoxy Alcohol ◽  
Theonella Swinhoei ◽  
Nmr Data ◽  
Chemical Shift Calculations

A total of eight new oxygenated 4-exo-methylene sterols, 1–8, together with one artifact 9 and six known sterols 11–16, were isolated from the marine sponge Theonella swinhoei collected from the Bohol province in Philippines. Structures of sterols 1–8 were determined from 1D and 2D NMR data. Among the sterols, 8α-hydroxytheonellasterol (4) spontaneously underwent an allylic 1,3-hydroxyl shift to produce 15α-hydroxytheonellasterol (9) as an artifact; this was rationalized by quantum mechanical calculations of the transition state. In addition, the 1,2-epoxy alcohol subunit of 8α-hydroxy-14,15-β-epoxytheonellasterol (5) was assigned using the Gauge-Independent Atomic Orbital (GIAO) NMR chemical shift calculations and subsequent DP4+ analysis. Finally, comparison of the 13C chemical shifts of isolated 7α-hydroxytheonellasterol (6) with the reported values revealed significant discrepancies at C-6, C-7, C-8, and C-14, leading to reassignment of the C-7 stereochemistry in the known structure.

scholarly journals Stereochemistry of Complex Marine Natural Products by Quantum Mechanical Calculations of NMR Chemical Shifts: Solvent and Conformational Effects on Okadaic Acid

Marine Drugs ◽  
2014 ◽  
Vol 12 (1) ◽  
pp. 176-192 ◽  
Author(s):  
Humberto Domínguez ◽  
Guillermo Crespín ◽  
Adrián Santiago-Benítez ◽  
José Gavín ◽  
Manuel Norte ◽  
...  
Keyword(s):  
Natural Products ◽  
Okadaic Acid ◽  
Marine Natural Products ◽  
Chemical Shifts ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
Nmr Chemical Shifts ◽  
Conformational Effects

scholarly journals Determination of the electron density in methyl (±)-(1S,2S,3R)-2-methyl-1,3-diphenylcyclopropanecarboxylate using refinements with X-ray scattering factors from wavefunction calculations of the whole molecule

2013 ◽  
Vol 69 (8) ◽  
pp. 910-914 ◽  
Author(s):  
John Bacsa ◽  
John Briones
Keyword(s):  
Electron Density ◽  
Title Compound ◽  
Cyclopropane Ring ◽  
Topological Analysis ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
X Ray ◽  
Compound C ◽  
X Ray Scattering

The molecule of the title compound, C18H18O2, is a substituted cyclopropane ring. The electron density in this molecule has been determined by refining single-crystal X-ray data using scattering factors derived from quantum mechanical calculations. Topological analysis of the electron densities in the three cyclopropane C—C bonds was carried out. The results show the effects of this substitution on these C—C bonds.

Benchmarking quantum mechanical calculations with experimental NMR chemical shifts of 2-HADNT

2015 ◽  
Vol 1086 ◽  
pp. 43-48 ◽  
Author(s):  
Yuemin Liu ◽  
Thomas Junk ◽  
Yucheng Liu ◽  
Nianfeng Tzeng ◽  
Richard Perkins
Keyword(s):  
Chemical Shifts ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
Nmr Chemical Shifts
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