Quantum Mechanical Calculation of ¹³C NMR Chemical Shifts in a Series of Isomeric Fucobiosides with the Account for Conformational Equilibrium

Abstract

Chemical shift calculations for isomeric fucobiosides were performed by means of quantum mechanics, taking into account the conformational equilibrium. It was found during our previous investigations that generally two conformers are present for the studied compounds. As was expected, the major differences of the chemical shift values between these conformers were found for the atoms in the area near the glycosidic linkage. Taking into account the relative weight of each conformer, we succeeded in obtaining a good coincidence of calculated and experimental chemical shifts for the compounds for which experimental shifts were known. The deviation was not more than 2 ppm.

Keywords:

• Fucoidans
• Structure elucidation
• NMR spectra
• Feed-forward neural network
• Adaptive resonance theory

ACKNOWLEDGEMENTS

This work was financed by the Russian Foundation for Basic Research (grant 10-03-01012-a) and the President of the Russian Federation (Grant for Young Scientists MK-5879.2008.3).

Notes

^aCalculated chemical shifts differed by less than 0.1 ppm.