Design, Semisynthesis, Insecticidal and Antibacterial Activities of a Series of Marine-Derived Geodin Derivatives and Their Preliminary Structure-Activity Relationships

To enhance the biological activity of the natural product geodin ( ), isolated from the marine-derived fungus sp., a series of new ether derivatives ( - ) was designed and semisynthesized using a high-yielding one-step reaction. In addition, the insecticidal and antibacterial activities of all geodin congeners were evaluated systematically. Most of these derivatives showed better insecticidal activities against Hübner than . In particular, showed potent insecticidal activity with an IC value of 89 μM, comparable to the positive control azadirachtin (IC = 70 μM). Additionally, , , , , and showed strong antibacterial activity against and with MIC values in the range of 1.15-4.93 μM. The preliminary structure-activity relationships indicated that the introduction of halogenated benzyl especially fluorobenzyl, into and substitution of 4-OH could be key factors in increasing the insecticidal and antibacterial activities of geodin.