Conformationally Mobile Acyclic Cucurbit[n]uril-Type Receptors Derived from an S-shaped Methylene Bridged Glycoluril Pentamer.

We report the synthesis of the conformationally mobile S-shaped glycoluril pentamer building block and two new acyclic CB[n]-type receptors and . (9 mM) and (11 mM) have moderate aqueous solubility but their host•guest complexes are poorly soluble. Host does not undergo intermolecular self-association whereas does (K = 189±27 M).