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The condensation of glycoluril and formaldehyde in concentrated HCl at 50 degrees C delivers nor-seco-cucurbit10uril (ns-CB 10). 1H NMR and X-ray crystallographic evidence indicates that the two cavities of ns-CB10 accommodate guests that are typically bound within CB6 or CB7. Several interesting types of selectivity are possible within these ternary complexes-top/center isomerism, diastereoselective complexation of chiral (but racemic) guest pairs, and guest size controlled homotropic allosterism.
Huang et al. (Sat,) studied this question.