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 ( 1 ), isolated from the marine-derived fungus Aspergillus sp., a series of new ether derivatives ( 2 - 37 ) 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 Helicoverpa armigera Hübner than 1 . In particular, 15 showed potent insecticidal activity with an IC 50 value of 89 μM, comparable to the positive control azadirachtin (IC 50 = 70 μM). Additionally, 5 , 12 , 13 , 16 , 30 and 33 showed strong antibacterial activity against Staphylococcus aureus and Aeromonas salmonicida 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 1 and substitution of 4-OH could be key factors in increasing the insecticidal and antibacterial activities of geodin.