Synthesis of Novel β-cyclodextrin Derivatives Bearing a 1-naphthyloxamino-oligo(ethyleneamino) Moiety and their Inclusion Complexation with some Fluorescent Dyes

摘要

Two novel β-cyclodextrin derivatives bearing a (1-naphthyloxamino)-ethyleneamino (4) or (1-naphthyloxamino)-diethylenediamino (5) moiety have been synthesized by a convenient method in 34% and 30% yields, respectively. Examinations of the circular dichroism (CD) spectra and fluorescence lifetime revealed that the naphthyloxamino-oligo (ethyleneamino) moiety tethered to β-cyclodextrin is not deeply embedded in the hydrophobic cavity of β-cyclodextrin itself even in the absence of a guest. The inclusion complexation behavior of 4 and 5 with some fluorescent dyes, i.e. ammonium 8-anilino-1-naphthalenesulfonate (ANS), sodium 2-(p-toluidinyl) naphthalenesulfonate (TNS), Acridine Red (AR) and Rhodamine B (RhB), was assessed in aqueous phosphate buffer solution (pH 7.2) at 25 ℃ by fluorometric titration to give the complex stability constants (K_S) and Gibbs free energy changes (ΔG~0) for the stoichiometric 1:1 inclusion complexation with the fluorescent dyes. The results obtained indicate that the naphthyloxamino-oligo (ethyleneamino) moiety attached to the β-cyclodextrin (1) can alter not only the original molecular binding-ability of the parent β-cyclodextrin, but also the molecular selectivity through the microenvironment changes of cyclodextrin cavity, which are discussed from the viewpoints of the size/shape-fit concept and the stereochemical complementary relationship between host cyclodextrin and model substrate.