Tight, oriented binding of an aliphatic guest by a new class of water-soluble molecules with hydrophobic binding sites

There is much current interest in the design and synthesis of water-soluble organic molecules with hydrophobic binding sites. A variety of interesting artificial receptors (hosts) based on cyclophane skeletons has been prepared and shown to bind flat, aromatic guests very efficiently. In contrast, efforts to bind other types of guests, such as derivatives of polycyclic aliphatic systems, have been less successful. We report herein that a new class of receptor molecules, which we have designed and synthesized, 7 binds a guest of this second type very effectively. Two binding modes are seen: one in which the guest is bound in a relatively random orientation and one which involves very much stronger binding with a very precise orientation of the guest in the binding site.