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Macrocycles with persistent shape and large, noncollapsible lumens have attracted increasing interest because of their unique properties and potential applications. Although most of the macrocycles with well-defined shape have hydrocarbon backbones formed from the stepwise coupling of sp- or sp2-hybridized carbon atoms,[1a,b,d, 2] macrocycles with other rigid backbones have also been reported. For example, we discovered a series of aromatic oligoamide macrocycles that could be generated in high yield by a one-pot macrocyclization process. These readily available macrocycles contain hydrophilic cavities that are rich in carbonyl oxygen atoms. With their persistent shape and noncollapsible cavities, these macrocycles have demonstrated unique features such as binding large cations with high affinity and specificity, and self-assembling into highly conducting transmembrane pores. The latest mechanistic study[4b] indicates that the folding of uncyclized oligoamide intermediates and precursors, which belong to a class of folding oligoamides with well-defined crescent conformations and tapelike backbones, plays a critical role in the observed high efficiency of the one-pot macrocyclization. The folding of the intermediates and precursors facilitates the one-pot cyclization, and at the same time impedes the formation of “overshooting” oligomers longer than the direct precursor of a macrocycle through remote steric hindrance.[4b] Herein we report that macrocycles with backbones other than aromatic oligoamides can also be formed with very high efficiency. Specifically, macrocycles with rigidified oligohydrazide backbones and nanosized cavities containing well-positioned, modifiable convergent sites can be obtained nearly exclusively in one step.
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