Synthesis of Monofacially Functionalized Cyclodextrins Bearing Amino Pendent Groups

Abstract

Derivatives of the cyclodextrins, αCD, βCD, and γCD, in which all primary hydroxyls are substituted by amine pendant groups, may be synthesized efficiently from the per-6-bromo-6-deoxy-CD derivatives by direct reaction with amines. These ACD derivatives, which bear six, seven, or eight amine pendent groups, represent interesting biomimetic receptors and catalysts. The synthetic strategy relies on quantitative transformation and efficient purification as is demonstrated by preparation of 11 homogeneous ACD derivatives. The limitations of the synthesis and potential adaptations are illustrated by the synthesis of several more ACD derivatives to >95% purity. A synthetic route to a CD persubstituted with primary amine functionalities at the primary face, per-6-(aminomethyl)-6-deoxy-CD, yields an alternative reagent to the simple per-6-amino-6-deoxy-CD, which is more suitable for further synthetic transformations. The synthetic strategy is further adapted to preparation of a prototypical (6 + 1)-ACD derivative in which one primary position is substituted with a sulfide group and the remaining six primary face positions are substituted with amine pendent groups.