Acid-activated clay as heterogeneous and reusable catalyst for the synthesis of bioactive cyclic ketal derivatives

Abstract

A new heterogeneous acid catalyst based on a natural resource, Tunisian clay (Clay-H0.5), has been preparedand characterized by FT-IR, FE-SEM, and powder X-ray diffraction (XRD), as well as chemical composition, cationexchange capacity, specific surface area, and pore volume. Acid treatment for 0.5 h enlarged the surface area from 78.24to 186.10 m2/g and pore volume (PV) from 0.186 to 0.281 cm3/g. The catalytic activity of this material was investigatedin ketalization reaction under mild solvent-free conditions. This achieved up to 92% isolated yield for only 10 wt.% of thecatalyst. This environmentally friendly method has advantages such as simple work-up procedure, avoidance of organicsolvents, and good performance in ketalization reactions. Importantly, the Clay-H0.5 catalyst showed good recyclabilitywhere insignificant activity loss was exhibited even after six runs. Synthesized cyclic ketals were tested for their possibleantileishmanial and antibacterial activities as well as antifungal activity. Biological screening showed that compound 11had important antileishmanial activity against both L. major and L. infantum, while compound 14 also had significantantibacterial activity against four gram-positive and two gram-negative bacteria, and antifungal activity against Candidaalbicans, with minimal inhibitory concentration values ranging from 15.62 µg/mL to 125 µg/mL.