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

• Published in: Organic & biomolecular chemistry 2010-01, Vol.8 (2), p.339-348
• Main Authors: Yang, Li, Qin, Song, Su, Xiaoyu, Yang, Fei, You, Jingsong, Hu, Changwei, Xie, Rugang, Lan, Jingbo
• Format: Article
• Language: English
• Subjects: Chemistry Techniques, Analytical - instrumentation; Crystallography, X-Ray; Fluorescent Dyes - chemical synthesis; Fluorescent Dyes - chemistry; Imidazoles - chemical synthesis; Imidazoles - chemistry; Models, Molecular; Molecular Conformation; Naphthalenes - chemistry; Solutions; Spectrophotometry, Ultraviolet; Stereoisomerism; Substrate Specificity; Tryptophan - analysis; Tryptophan - chemistry; Water - chemistry
• ISSN: 1477-0520; 1477-0539
• DOI: 10.1039/b908540h

A type of 1,1'-binaphthyl-based imidazolium chemosensor module has been synthesized for the highly selective recognition of tryptophan (Trp) among the eleven alpha-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)- with l-Trp are superior to those of (R)-. In spite of an inferior selectivity towards various aromatic amino acids, the macrocyclic (R)- displays a remarkable enantiodiscrimination for the two enantiomers of tryptophan with a K(D)/K(L) value as high as 6.2.