Stabilization of a <i>Cis</i> Amide Bond in a Host−Guest Complex
作者:Glen J. Pernía、Jeremy D. Kilburn、Jonathan W. Essex、Russell J. Mortishire-Smith、Michael Rowley
DOI:10.1021/ja9607805
日期:1996.1.1
Macrobicycle 12 has been synthesized and its binding properties with a range of N-acetyl amino acid carboxylates (as tetrabutylammonium salts) have been studied. While the binding results showed little selectivity for the various substrates investigated, detailed NMR studies have revealed that D-amino acid substrates bind predominantly on the outside of the macrobicycle cavity by a strong carboxylate-thiourea interaction, whereas L-amino acid substrates bind predominantly on the inside of the cavity also establishing a strong carboxylate-thiourea interaction but with the acetyl amide in a cis configuration. Molecular modeling studies suggest that the energetic penalty associated with adopting a cis amide configuration in the host-guest complex is compensated by intermolecular hydrogen bonds between the cis amide and the rim of the macrobicycle.