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

Abstract

Two novel g -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 g -cyclodextrin is not deeply embedded in the hydrophobic cavity of g -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 25C by fluorometric titration to give the complex stability constants ( K S ) and Gibbs free energy changes ( j G 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 g -cyclodextrin ( 1 ) can alter not only the original molecular binding-ability of the parent g -cyclodextrin, but also the molecular selectivity through the micro-environment 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.