Divergent Synthesis and Evaluation of Inhibitory Activities against Cyclooxygenases-1 and -2 of Natural Withasomnines and Analogues

Abstract

The divergent synthesis of natural withasomnines and analogues was achieved from 4-hydroxypyrazoles, which was prepared via alkaline hydrolysis of the Baeyer–Villiger oxidation products from 4-formylpyrazoles. Key steps of this synthesis are regioselective Claisen rearrangement of 4-allyloxypyrazoles and the Suzuki–Miyaura coupling of 5,6-dihydro-4H-pyrrolo[1,2-b]pyrazol-3-yl trifluoromethanesulfonate and commercially available arylboronic acids. The Suzuki–Miyaura coupling at the final step of this strategy enabled facile access to natural withasomnines and their analogues. The biological activities of the twelve synthesized compounds against cyclooxygenases-1 and -2 (COX-1 and COX-2) were evaluated.