= Solution
The terminal \b[<ureidopyrimidinone> groups] supply the association sites. Their <urea>/pyrimidinone NH donors and <carbonyl>/ring-nitrogen acceptors can form a self-complementary array of four <hydrogen bonds> between two <UPy units>. Joining the two terminal units of one <molecule> by this noncovalent association closes the ring.
The ether-containing arms provide flexibility and spacing; they are not covalently joined together during ring formation. The ring is therefore a supramolecular <conformation> of the existing <molecule>, rather than a new covalent <ether> <macrocycle>.
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