Using computational methods to predict NMR spectra for polyether compounds

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
Krysten Scott Adams (Creator)
The University of North Carolina Wilmington (UNCW )
Web Site:
Ned Martin

Abstract: Naturally occurring polyether ring compounds have been studied extensively over the past several years because of their importance as biologically active hemolytic and neurotoxic substances produced by various marine phytoplankton species. These substances contain varying numbers of ether rings of varying sizes. This research was performed to predict NMR spectra, including chemical shifts and coupling constants, of such polyether ring compounds. A literature search was performed to determine the frequency of ring size occurrence within the known toxins and each structure was broken down into three-ring segments. Models of each of these three-ring substructures were built in Spartan and a conformer search was done followed by a semi-empirical energy minimization on the lower energy conformers. Once the most energetically favorable conformers of each compound were determined, they were submitted to the North Carolina Supercomputing Center to perform a Hartree-Fock single point energy calculation, as well as a calculation of isotropic shielding values using the GIAO (Gauge including atomic orbital) method. From these values, chemical shifts were calculated. Energy values were used to determine the distribution among the various conformers by using a Boltzmann function. With this distribution data a prediction of chemical shifts for each ring structure was developed as the weighted average of the chemical shifts computed for each contributing conformer. Proton-proton coupling constants were also calculated using dihedral angles measured from the several minimum energy conformers and applying a modified Karplus equation to each one. Again, application of the Boltzmann function gave a weighted average coupling constant. These numbers were used to produce a library of NMR spectral data, which should be useful for determining the structures of novel polyether toxins.

Additional Information

A Thesis Submitted to the University of North Carolina at Wilmington in Partial Fulfillment Of the Requirements for the Degree of Master of Science
Language: English
Date: 2009
Nuclear magnetic resonance spectroscopy, Polyethers, Spectrum analysis
Nuclear magnetic resonance spectroscopy
Spectrum analysis

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