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Paper

Org. Biomol. Chem., 2010, 8, 339 - 348, DOI: 10.1039/b908540h

1,1-Binaphthyl-based imidazolium chemosensors for highly selective recognition of tryptophan in aqueous solutions

Li Yang, Song Qin, Xiaoyu Su, Fei Yang, Jingsong You, Changwei Hu, Rugang Xie and Jingbo Lan

A type of 1,1-binaphthyl-based imidazolium chemosensor module has been synthesized for the highly selective recognition of tryptophan (Trp) among the eleven -amino acids investigated in aqueous solutions via synergistic effects of multiple hydrogen bonding and electrostatic interactions. These results have demonstrated that the C-2 hydrogen atom of the imidazolium ring plays a key role as a hydrogen bond donor. The UV/vis, fluorescence and mass spectral studies have indicated that a 1:1 complex is formed between the host and tryptophan. The binding affinity and selectivity of the cleft-like receptor (R)- 1 with L-Trp are superior to those of (R)- 2–5. In spite of an inferior selectivity towards various aromatic amino acids, the macrocyclic (R)- 3 displays a remarkable enantiodiscrimination for the two enantiomers of tryptophan with a KD/KL value as high as 6.2.

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