Structural optimization and evaluation of butenolides as potent antifouling agents: modification of the side chain affects the biological activities of compounds

Abstract

A recent global ban on the use of organotin compounds as antifouling agents has increased the need for safe and effective antifouling compounds. In this study, a series of new butenolide derivatives with various amine side chains was synthesized and evaluated for their anti-larval settlement activities in the barnacle, Balanus amphitrite. Side chain modification of butenolide resulted in butenolides 3c-3d, which possessed desirable physico-chemical properties and demonstrated highly effective non-toxic anti-larval settlement efficacy. A structure-activity relationship analysis revealed that varying the alkyl side chain had a notable effect on anti-larval settlement activity and that seven to eight carbon alkyl side chains with a tert-butyloxycarbonyl (Boc) substituent on an amine terminal were optimal in terms of bioactivity. Analysis of the physico-chemical profile of butenolide analogues indicated that lipophilicity is a very important physico-chemical parameter contributing to bioactivity.

Keywords:

• antifouling
• anti-larval settlement
• barnacle
• butenolides
• structural optimization
• side chain modification
• lipophilicity

Acknowledgements

This study was supported by a grant (DY125-15-T-02) from the China Ocean Mineral Resources Research and Development Association, a joint research grant from the Research Grants Council of the HKSAR and the National Natural Science Foundation of China (N_HKUST602/09), and award SA-C0040/UK-C0016 from the King Abdullah University of Science and Technology to P.Y. Qian.