ИСТИНА

p-Sulfonatocalixarenes are well-known for their solubility in water and low toxicity, that make these molecular scaffold attractive for construction of novel polyfunctional molecules to be used for complexation with neutral and charged substrates as well as in catalysis, biochemistry, medicine etc. Still, there are very limited range of functionalities that can be introduced at calixarenes’ narrow rims and survive under drastic sulfonation conditions. Oppositely, solubility issues and altered acidities of OH-groups interfere significantly the application of well-known alkylation/acylation methods for a post-modification of p-sulfonatocalixarenes having no substituents at narrow rims. Thus, the development of novel approaches for functionalization of p-sulfonatocalixarenes seems attractive and important task. In this work, both approaches to functionalization of p-sulfonatocalixarenes were extended (Figure 1). First, the previously inaccessible water-soluble calix[4]arenes having four sulfonate groups at wide rims and four or two 2-hydroxyethyl units, as well as two substituted triazole groups at narrow rims were prepared by direct sulfonation of pre-functionalized p-tBu- or p-H-calix[4]arenes by bis(trifluoroacetyl)sulfate in dichloromethane/trifluoroacetic anhydride medium. The second way utilized the introduction of four propargyl groups to narrow rim of p-sulfonatocalix[4]arene followed by their conversion into substituted triazoles under copper(I)-catalyzed azide–alkyne cycloaddition conditions. The latter approach seemed universal and allowed the preparation of diversely functionalized p-sulfonatocalixarenes with four ester, benzyl and even multifunctional tripeptide units linked to the narrow rim of the platform through triazole units as key motifs.