ИСТИНА

First reported in 1997, calix[4]tubes have attracted interest due to their selectivity for K+ and unique cation complexation mode that can be used to mimic cellular ion channels behavior. Upper-rim functionalization of calixtubes is of great importance for development and applications of these host systems. But chemical modifications of calixtubes are weakly reported and are limited to halogenation of calixtubes1 and modifications of adamantylated calixtubes.2 Here we present an approach to direct functionalization of calixtubes’ upper rims. Exhaustive nitration of various calixtube substrates led to fully nitrated calix[4]tube in high yield. Reduction of the nitro groups gave the corresponding octaamine, and its octakis(hydrochloride) is the first water-soluble calix[4]tube. The presence of amino groups allows various further chemical modifications of calixtubes. Thus we converted the octaamine to calixtube containing eight urea moieties. It is known that calix[4]arenes containing four urea groups at upper rims are able to form molecular capsules.1 The selective formation of hetero- or homo-dimers by octaurea calixtubes can be used for the construction of self-assembled polymers or oligomers. According to preliminary data, the obtained octaurea calixtube is capable of forming trimeric aggregates with two molecules of tetraurea calix[4]arenes.