Isolation of a new butenolide from the South China Sea gorgonian coral Subergorgia suberosa

Chemical investigation on the South China Sea gorgonian coral Subergorgia suberosa has led to the isolation of one new butenolide (5R)-5-(1-ethoxypropyl)-5-hydroxy-3,4-dimethylfuran-2(5H)-one (1) as a pair of inseparable epimers, along with two known butenolides (S)-5-hydroxy-3,4-dimethyl-5-propylfuran-2(5H)-one (2) and (S)-5-hydroxy-3,4-dimethyl-5-pentylfuran-2(5H)-one (3). Their structures including absolute configurations were determined unambiguously by detailed analyses of spectroscopic data and by comparison with the available literature. Compounds 1-3 exhibited moderate antifouling activities against the settlement of Balanus amphitrite larvae, whereas compound 4, the acetyl derivative of 3, showed no antifouling activity at the concentrations up to 25g/mL.