| Abstract
| - The cucurbit[n]uril (CB[n]) family of macrocycles occupies a prominent role in molecular recognitionand self-assembly studies despite the current inability to access specific cucurbit[n]uril homologues,derivatives, and analogues by straightforward tailor-made synthetic procedures. In this paper, weexplore an approach that circumvents the challenges posed by the tailor-made synthesis ofmacrocyclic CB[n] by preparing 1, which functions as an acyclic CB[6] congener. The o-xylyleneconnections to the glycoluril rings preorganize 1 into the (a,a,a,a)-1 conformation required for bindingand reduce its tendency to undergo self-association. We surveyed the binding properties of 1 toward16 amines (Ka ≤ 1.52 × 104 M-1) and diol, diacid, guanidinium, and pyridinium species in pD 7.4phosphate-buffered D2O. We find that the recognition properties of 1 parallel those of CB[6], bindingtightly to alkaneammonium species in water and exhibiting length-dependent selectivity andcompetitive binding with alkali metals present in solution. Compound 1 binds hexanediammoniumion only 180-fold less tightly than CB[6]. The modular synthesis of 1 suggests synthetic methodstoward the preparation of acyclic CB[n] congeners with complex functional groups on the edges oftheir aromatic rings and cavity volumes similar to CB[7] and CB[8]. In combination, these resultssuggest that acyclic CB[n] congeners hold promise in molecular recognition and self-assembly studiesthat complements that of macrocyclic CB[n].
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