The relevance of carbohydrate hydrogen-bonding cooperativity effects: a cooperative 1,2-trans-diaxial diol and amido alcohol hydrogen-bonding array as an efficient carbohydrate-phosphate binding motif in nonpolar media.
Carbohydrates with suitably positioned intramolecularly hydrogen-bonded hydroxyl and amide groups have the potential to act as efficient bidentate phosphate binders by taking advantage of sigma- and/or ,sigma,pi-H-bonding cooperativity in nonpolar solvents. Donor-donor 1,2-trans-diaxial amido alcohol (1) and diol (3), in which one of the donor centres is cooperative, are very efficient carbohydrate-phosphate binding motifs. We have proven and quantified the key role of hydrogen-bonding centres indirectly involved in complexation, which serve to generate an intramolecular H-bond (six-membered cis H-bond) in 1 and 3. This motif enhances the donor nature of the H-bonding centres that are directly involved in complexation. A comparison of the thermodynamic parameters of the complexes formed between phosphate and a cooperative (1-Phos) or anti-cooperative (2-Phos) bidentate H-bonded motif of a carbohydrate has allowed us to quantify the energetic advantage of H-bonding cooperativity in CDCl3 and CDCl3/CCl4 (1:1.3) (Delta Delta G degrees=-2.2 and -2.0 kcal mol(-1), respectively). The solvent dependences of the entropy and enthalpy contributions to binding provide a valuable example of the delicate balance between entropy and enthalpy that can arise for a single process, providing effective cooperative binding in terms of Delta G degrees.
Muñoz
Eva Maria
EM
López de la Paz
Manuela
M
Jiménez-Barbero
Jesús
J
Ellis
Gary
G
Pérez
Marta
M
Vicent
Cristina
C
D002241:Carbohydrates / Q000737:chemistry*; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D009005:Monosaccharides / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013816:Thermodynamics
D002241:Carbohydrates; D009005:Monosaccharides; D010710:Phosphates