Authors: Xiaocong Wang Robert J Woods
Publish Date: 2016/03/12
Volume: 64, Issue: 4, Pages: 291-305
Abstract
A twostate model is commonly used for interpreting ring conformations of furanoses based on NMR scalar 3 Jcoupling constants with the ring populating relatively narrow distributions in the North and the South of the pseudorotation itinerary The validity of this simple approach has been questioned and is examined here in detail employing molecular dynamics MD simulations with a new GLYCAM force field parameter set for furanoses Theoretical 3 Jcoupling constants derived from unrestrained MD simulations with the new furanosespecific parameters agreed with the experimental coupling constants to within 1 Hz on average The results confirm that a two state model is a reasonable description for the ring conformation in the majority of methyl furanosides However in the case of methyl αDarabinofuranoside the ring populates a continuum of states from North to South via the eastern side of the pseudorotational itinerary Two key properties are responsible for these differences Firstly East and West regions in β and αanomers respectively are destabilized by the absence of the anomeric effect And secondly East or West conformations can be further destabilized by repulsive interactions among vicinal hydroxyl groups and ring oxygen atoms when the vicinal hydroxyl groups are in synconfigurations such as in ribose and lyxose more so than when in anti arabinose xylose
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