Calix[4]arene Sulfonate Hosts Selectively Modified on the Upper Rim: A Study of Nicotine Binding Strength and Geometry

Abstract

Preprint manuscript, including synthesis of new compounds and fluorescence/NMR-based binding data. <div><br></div><div>We present the synthesis and structure-activity relationships of sulfonatocalix[4]arene hosts bearing novel substitutions. The calix[4]arenes are modified on the upper rim at either one or two of the phenolic units, where the dual modifications are introduced selectively on neighboring or opposing phenols. The calix[4]arenes are mono- or di-functionalized with nitro or formyl groups, with the remaining upper-rim sites in all cases occupied by sulfonates. Equilibrium association constants were determined between each host and the guests nicotine, nornicotine, and cotinine. Indicator displacement-based binding studies show that nicotine binds most strongly to the different members of the library followed by nornicotine, whereas cotinine displays weak to no binding. NMR titrations were carried out with nicotine and show different host-guest interaction geometries for the formyl-calix[4]arenes versus the nitro-calix[4]arenes. <div><p></p></div></div>

Binding methylarginines and methyllysines as free amino acids: a comparative study of multiple supramolecular host classes

“…The binding constants were determined for the complexes formed by each member of the host library with each of the guests, using indicator displacement assays (IDAs). We adapted previously reported IDAs 31 for sCx4 (using lucigenin, Figure 2b) 32 and M1 and M2 (using Rhodamine 6G, Figure 2b). 33,34 We established IDAs for PC and CLR01 during this work.…”