M. Narita et F. Hamada, The synthesis of a fluorescent chemo-sensor system based on regioselectively dansyl-tosyl-modified beta- and gamma-cyclodextrins, J CHEM S P2, 4, 2000, pp. 823-832
Citations number
23
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
Flexible bis-functionalized hosts, 6(A)-dansyl-6(X)-tosyl-modified beta-cyc
lodextrins (X=B or G, C or F, and D or E for beta-1, beta-2, and beta-3, re
spectively) and gamma-cyclodextrins (X=B or H, C or G, D or F, and E for ga
mma-1, gamma-2, gamma-3, and gamma-4, respectively) have been synthesized t
o investigate their chemo-sensor potential for organic compounds such as bi
le acids and terpenoids. These host compounds show pure monomer fluorescenc
e, the beta-analogs showing a decrease in fluorescence intensity on accommo
dation of all the guests examined. On the other hand, gamma-analogs exhibit
a decrease in intensity on complexation of bile acids and smaller guests s
uch as bicyclic molecules, but an increase in intensity for much smaller gu
ests such as monocyclic and non-cyclic molecules. The extent of fluorescenc
e variation with a guest is employed to display the sensing ability of the
hosts. The sensing parameter (Delta I/I-0) was used to describe the sensing
ability of the hosts. Host beta-analogs can detect chenodeoxycholic acid,
ursodeoxycholic acid, and (-)-borneol with high sensitivity. The sequence o
f binding ability of these hosts is beta-1 >beta-2 >beta-3 for bile acids,
and beta-2 >beta-1 greater than or equal to beta-3 for terpenoids. On the o
ther hand, gamma-analogs can detect lithocholic acid, chenodeoxycholic acid
, ursodeoxycholic acid, and (-)-borneol with high sensitivity. The sensing
parameters of beta-analogs are up to almost two times larger for ursodeoxyc
holic acid and three times for (-)-borneol in comparison with those of gamm
a-analogs. The behavior of the appended moieties of the hosts during host-g
uest complexation is studied by induced circular dichroism (ICD), fluoresce
nce, and H-1 NMR spectra. Host beta- and gamma-analogs show similar ICD spe
ctral patterns. Host gamma-analogs exhibit H-1 NMR spectral changes after a
ddition of ursodeoxycholic acid, whereas beta-analogs indicate no change. T
he guest-induced variations in ICD, fluorescence, and H-1 NMR spectra sugge
st that the dansyl and tosyl groups change their mutual relationship.