SCHEDULED MAINTENANCE
Azacalixarene: synthesis, conformational analysis, and recognition behavior toward anions
Abstract
The synthesis of an azacalix[4]arene (4) having four primary amino groups on the upper rim has been achieved. The synthesis was accomplished by a one-step cyclization starting from two easily synthesized building blocks. 1H NMR spectra indicate that this azacalixarene prefers a cone conformation, but that rapid interconversion among different conformations occurs at room temperature. It is shown that 4 is a useful receptor for sensing various anionic guests, such as inositol triphosphate (IP3), in aqueous solution. In a competition binding assay, fluorescent probes bound within 4 were replaced by anionic guests in buffered aqueous solution, causing a modulation in the fluorescence intensity. NMR spectra of 4 in the presence of fructose 1,6-diphosphate suggest that this guest is bound inside the cavity which adopts a cone conformation.
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