Identification of intramolecular hydrogen bonds as the origin of malfunctioning of multitopic receptors

Several trisamides of N,N-bis(2-aminoethyl)ethane-1,2-amine are prepared as potential saccharide receptors. Surprisingly low or even nil affinity to n-octyl-glucose is found by H-1 NMR titration, and explained as a consequence of intramolecular hydrogen bonds of trisamides, (R-CO-NH-C2H4)(3)N. The hydrogen bonds are identified by combination of H-1 NMR and infrared spectra, and H-1 NMR temperature coefficients. Results demonstrate that even small molecule can has a rather strong secondary structure, which can cause their malfunctioning in certain applications. Results also point out that the amide temperature coefficients should not be used as the only parameter for the consideration a hydrogen bond is intermolecular or intramolecular, particularly, in the case of furcated hydrogen bonds, and in the cases were a couple of signals are averaged. (c) 2012 Published by Elsevier B.V.