Iminecalix[4]arenes: microwave-assisted synthesis, X-ray crystal structures, and anticandidal activity

Abstract

In this study, six iminecalix[4]arenes were synthesized and the crystal structures of two of the iminecalix[4]arenes were also determined. Iminecalix[4]arene adopts a strongly pinched cone conformation with two upper rim substituents pointing toward and the other two pointing away from the aromatic cavity. This uncommon conformation is stabilized by an intramolecular π…π interaction between the phenyl rings from the upper rim substituents pointing inwards the cone. In addition, phenyl rings from the substituent groups are not coplanar with respect to the calixarene phenyl rings holding them. The compounds, as well as their respective monomeric units, were evaluated for their antifungal activities against Candida strains. All the synthesized iminecalix[4]arenes were found to cause higher inhibition of all tested Candida strains than their respective monomers. The ratio between the minimal inhibitory concentration (MIC) of a monomer and the corresponding iminecalix[4]arene ranged from 2.05 to 36.50. Furthermore, the iminecalix[4]arene bearing nitrofuran group exhibited low MIC values comparable to that of fluconazole. Thus, this compound was twice more active than fluconazole against Candida krusei.