Synthesis of andrographolide-related esters as insecticidal and acaricidal agents.

In continuation of our program aimed at the development of natural product-based pesticidal agents, a series of andrographolide-related esters, such as 3,19-dialkyl(aryl)carbonyloxy andrographolide (3a-g), 3-alkyl(aryl)carbonyloxyandrographolide (4a-g), and 19-alkyl(aryl)carbonyloxyandrographolide (5a-g), were prepared. Their structures were well characterized by1 H NMR, IR, optical rotation, HRMS and mp. Especially three-dimensional structures of compounds 3a, 4g, and 5g were unambiguously confirmed by single-crystal X-ray diffraction. Compounds 3a and 5a exhibited good insecticidal and acaricidal activities against Mythimna separata and Tetranychus cinnabarinus. Their structure-activity relationships were also discussed.