Conformational Plasticity in Glycomimetics: Fluorocarbamethyl-L-idopyranosides Mimic the Intrinsic Dynamic Behaviour of Natural Idose Rings.

Chemistry (Weinheim an der Bergstrasse, Germany)

PubMedID: 26096911

Unione L, Xu B, Díaz D, Martín-Santamaría S, Poveda A, Sardinha J, Rauter AP, Blériot Y, Zhang Y, Cañada FJ, Sollogoub M, Jiménez-Barbero J. Conformational Plasticity in Glycomimetics: Fluorocarbamethyl-L-idopyranosides Mimic the Intrinsic Dynamic Behaviour of Natural Idose Rings. Chemistry. 2015;21(29):10513-10521.
Sugar function, structure and dynamics are intricately correlated. Ring flexibility is intrinsically related to biological activity; actually plasticity in L-iduronic rings modulates their interactions with biological receptors. However, the access to the experimental values of the energy barriers and free-energy difference for conformer interconversion in water solution has been elusive. Here, a new generation of fluorine-containing glycomimetics is presented. We have applied a combination of organic synthesis, NMR spectroscopy and computational methods to investigate the conformational behaviour of idose- and glucose-like rings. We have used low-temperature NMR spectroscopic experiments to slow down the conformational exchange of the idose-like rings. Under these conditions, the exchange rate becomes slow in the (19) F NMR spectroscopic chemical shift timescale and allows shedding light on the thermodynamic and kinetic features of the equilibrium. Despite the minimal structural differences between these compounds, a remarkable difference in their dynamic behaviour indeed occurs. The importance of introducing fluorine atoms in these sugars mimics is also highlighted. Only the use of (19) F NMR spectroscopic experiments has permitted the unveiling of key features of the conformational equilibrium that would have otherwise remained unobserved.