Building Blocks for Articicial Anion Receptors: Derivatives of Chiral Bicyclic Guanidines

Bicyclic guanidinium salts are versatile anchor groups for oxoanions. Their incorporation into modular artificial hosts calls for the reliable accessibility of chiral, regioselectively functionalized derivatives. Here the preparation of an ensemble 6-14 of suitable building blocks is described, which meets these requirements and may be introduced into polytopic receptors by various nucleophilic displacement reactions. The individual members of this class were conveniently prepared in satisfactory yield by functional group manipulation starting from the known differentially protected parent compound 4.