ISSN:
1573-1111
Keywords:
Barbiturate receptors
;
stability constants
;
molecular modelling
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
Notes:
Abstract Three new derivatives of 2,6-diacyldiaminopyridine are reported. NMR shift titrations were performed in CDCl3 with barbiturates. The diamide1 affords a greater complexation energy (−13.00 kJ mol−1) with bemegride than the dithioamide2 (−9.15 kJ mol−1). This result, unexpected on the basis of the proton acidities, is explained by the great torsion energy induced in2 by the bulky sulfur atom. Compounds3 and4 present unusual four and five H-bond features with barbital and relatively weak complexation energies (−9.53 and −16.34 kJ mol−1, respectively). Molecular mechanics indicates that ligand4 displays a helical secondary structure which is disrupted by complexation. Calculations of the H-bond energies (ΔE calc.) of the intermolecular assemblies with barbital or phenobarbital and other host-guest complexes given in the literature give a good correlation (r=0.98) with experimental values: ΔE calc.=1.07 ΔG a−42.0. Limitations of this relation are discussed.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00706938
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