Issue 4, 2000

The synthesis of a fluorescent chemo-sensor system based on regioselectively dansyl-tosyl-modified β- and γ-cyclodextrins

Abstract

Flexible bis-functionalized hosts, 6A-dansyl-6X-tosyl-modified β-cyclodextrins (X = B or G, C or F, and D or E for β-1, β-2, and β-3, respectively) and γ-cyclodextrins (X = B or H, C or G, D or F, and E for γ-1, γ-2, γ-3, and γ-4, respectively) have been synthesized to investigate their chemo-sensor potential for organic compounds such as bile acids and terpenoids. These host compounds show pure monomer fluorescence, the β-analogs showing a decrease in fluorescence intensity on accommodation of all the guests examined. On the other hand, γ-analogs exhibit a decrease in intensity on complexation of bile acids and smaller guests such as bicyclic molecules, but an increase in intensity for much smaller guests such as monocyclic and non-cyclic molecules. The extent of fluorescence variation with a guest is employed to display the sensing ability of the hosts. The sensing parameter (ΔI/I0) was used to describe the sensing ability of the hosts. Host β-analogs can detect chenodeoxycholic acid, ursodeoxycholic acid, and (−)-borneol with high sensitivity. The sequence of binding ability of these hosts is β-1 > β-2 > β-3 for bile acids, and β-2 > β-1 ≥ β-3 for terpenoids. On the other hand, γ-analogs can detect lithocholic acid, chenodeoxycholic acid, ursodeoxycholic acid, and (−)-borneol with high sensitivity. The sensing parameters of β-analogs are up to almost two times larger for ursodeoxycholic acid and three times for (−)-borneol in comparison with those of γ-analogs. The behavior of the appended moieties of the hosts during host–guest complexation is studied by induced circular dichroism (ICD), fluorescence, and 1H NMR spectra. Host β- and γ-analogs show similar ICD spectral patterns. Host γ-analogs exhibit 1H NMR spectral changes after addition of ursodeoxycholic acid, whereas β-analogs indicate no change. The guest-induced variations in ICD, fluorescence, and 1H NMR spectra suggest that the dansyl and tosyl groups change their mutual relationship.

Article information

Article type
Paper
Submitted
23 Sep 1999
Accepted
23 Dec 1999
First published
13 Mar 2000

J. Chem. Soc., Perkin Trans. 2, 2000, 823-832

The synthesis of a fluorescent chemo-sensor system based on regioselectively dansyl-tosyl-modified β- and γ-cyclodextrins

M. Narita and F. Hamada, J. Chem. Soc., Perkin Trans. 2, 2000, 823 DOI: 10.1039/A907702B

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