Potent Antifouling Resorcylic Acid Lactones from the Gorgonian-Derived Fungus Cochliobolus lunatus

Three new 14 membered resorcylic acid lactones, two with a rare natural acetonide group and one with a 5-chloro-substituted lactone, named cochliomycins A-C (1-3), together with four known analogues, zeaenol (4), LL-Z1640-1 (5), LL-Z1640-2 (6), and paeciloniycin F (7), were isolated from the culture broth of Cochliobolius lunatus, a fungus obtained from the gorgonian. Dichotella gemmmacea collected in the South China Sea Their structures and the relative configurations of 1-3 were elucidated using comprehensive spectroscopic methods including NOESY spectra and chemical conversions. A transetherification reaction was also observed in which cochliomycin:B (2) in a, solution of CDCl3 slowly rearranged to give cochliomycin A (4) at room temperature. These resorcylic acid lactones were evaluated against the larval settlement of barnacle Balanus amphitrite and antifouling activity was detected for the first time for this class of metabolites. The antibacterial and cytotoxfc activities of these. compounds were alsoexamined.