Dendrimer poly(ethylenimine)s linked to beta-cyclodextrin

beta-Cyclodextrin was attached to two dendrimer poly(ethylenimine)s. The resulting cyclodextrin-containing dendrimers, CD-I and CD-II, can be considered either as dendrimers equipped with specific binding sites or as cyclodextrins containing amino groups around the cavities. Amines of CD-I and CD-II remarkably resisted protonation compared with those of the parent dendrimers. A compact conformation of CD-I or CD-II in which the dendrimer wraps itself around the cyclodextrin is proposed as a conformation consistent with the suppressed protonation. Esters containing t-butylphenyl groups were complexed by CD-I and CD-II and underwent fast deacylation. Kinetic data were obtained with several ester substrates, which revealed that two amino groups located in the vicinity of each cyclodextrin cavity of CD-I or CD-II participated as nucleophiles. In addition, optimum reactivity was attained when the spacer connecting the t-butylphenyl and the ester groups was -O-CH2- or -CH=CH-. Structures of the active sites for the accelerated deacylation of esters were elucidated on the basis of the kinetic data. (C) 1997 Academic Press.