STUDIES ON SEARCH FOR ANTI-FOULING SUBSTANCES AND THEIR DEVELIPMENTS

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In our search for compounds to prevent biofouling, we have focused on the formation of the microbial biofilm that covers a surface that has been newly immersed in seawater. Antibacterial activity against the marine bacterium Rhodospirillum salexigens SCRC-113 strain, which has an adhering property, was selected as a bioassay to identify such compounds.More than 10 compounds, including novel zamamistatin, hedathiosulfonic acids, N-γ-glutamylboletione, tribromacetamide derivatives and so on, were isolated and their chemical structures were determined by careful pectroscopic analysis. The absolute stereochemistries of zamamistatin and hedathiosulfonic acids were determined using the modified Mosher's method. Two enantiomers of N-γ-glutamylboletione were synthesized to confirm its absolute stereostructure.Both nakitroiol and N-γ-glutamylboletione have been synthesized and a total synthetic study has been started for zamamistatin. Field experiments for actual antifouling capabilities are in progress. Recently, a photochemical reaction of titanium oxide with the generation of superoxide anion has been reported as a new antifouling method. However, the final answer to resolve biofouling problems has not been found. Therefore, it is important to continue to search for other candidates.We have also studied the action mechanism of these antibacterial compounds. Some of them may have future medical applications ; for example, N-benzyl-N-methyl-tribromacetamide and the related compound 4-tribromo-3-oxobutyl-benzene have been suggested as possible anti-cancer drugs. Basic investigations are now underway.This research project has demonstrated that our strategy for identifying new environmentally acceptable antifouling substances can lead to some extremely remarkable compounds.