Isocyano compounds as non-toxic antifoulants.

The marine sponge Acanthella cavernosa and nudibranchs of the family Phyllidiidae contain isocyanoterpenoids and their related compounds that show potent antifouling activity against cypris larvae of the barnacle Balanus amphitrite, while their toxicity to cyprids is weak. To develop non-toxic antifoulants based on isocyanoterpenoids, especially 3-isocyanotheonellin, a total of 36 isocyano compounds have been synthesized. They were evaluated by both antifouling activity and toxicity toward B. amphitrite cyprids, which led some insight into the structure-activity relationships. Since linear alkyl isocyanides showed antifouling activity at nontoxic concentrations, a large amount of 1,1-dimethyl-10-undecyl isocyanide was synthesized, incorporated into paints, and tested for antifouling activity in the field with promising results. Therefore, isocyano compounds were considered as candidate non-toxic antifouling agents.