I. Suzuki et al., Molecular recognition of deoxycholic acids by pyrene-appended gamma-cyclodextrin connected with a rigid azacrown spacer, CHEM PHARM, 47(2), 1999, pp. 151-155
A gamma-cyclodextrin (gamma-CyD) derivative (1) having a pyrene moiety, con
nected through a 4,13-diaza-18-crown-6 ether moiety to gamma-CyD, was synth
esized and evaluated for guest binding and sensing properties. In aqueous s
olution, 1 existed as an association dimer in which the secondary hydroxyl
sides faced each other to accommodate two pyrene moieties, Photo-induced el
ectron transfer (PET) between the amino group and the excited pyrene moiety
regulated the monomer fluorescence intensity of 1. The monomer-dimer equil
ibrium and the PET indicated that 1 may be used as a host capable of detect
ing guest complexation by changes in fluorescence intensity from the pyrene
moiety, Deoxycholic acids were found to be good guests for detection by 1,
and deoxycholic acid itself induced different fluorescence changes compare
d to the other deoxycholic acids. This indicated that 1 could recognize the
position of the hydroxy groups on the steroidal framework. The azacrown pa
rt may participate in the guest selectivity for the deoxycholic acids by re
gulating the distance between the amino group and the pyrene moiety, modify
ing PET efficiency.