Marine biofouling is the process of micro- and macro-organisms adhering to and growing on a submerged surface such as the hull of a ship, tidal power generators, oil rigs and other such marine structures. ¹ It is a complex, multistage process involving a range of physical and chemical effects that impacts every marine based industry, with major associated economic and environmental costs.   In the shipping industry, the added drag due to biofouling has been observed to increase fuel consumption by up to 40%, dramatically increasing not only financial cost, but also greenhouse gas emissions. ² Other issues such as increased maintenance, like hull cleaning and repair due to increased corrosion, also add to the costs of biofouling, with an estimated global impact of $36 billion USD per annum. Previous attempts at preventing marine biofouling have involved the use of highly toxic organo-tin compounds that accumulate in the environment causing unwanted toxicity. However, in 2008, organo-tin coatings were banned by the world maritime organisation. ³ Since then there has been a major push in the antifouling industry to develop eco-friendly alternatives.

The present research aims to employ cyclic dipeptides to combat this global issue in an environmentally sound fashion. 2,5-Diketopiperazines present an attractive target due to their relative stability to proteolytic degradation compared, to linear peptide equivalents, and the ability to generate structural analogues efficiently through the use of different amino acids. Following a known pharmacophore and previous unpublished work completed by Johan Svenson and co-workers at RISE (Research Institute of Sweden), a library of 2,5-diketopiperazines was designed, synthesised and evaluated as novel antifouling agents. ⁴ These 2,5-diketopiperazines have been shown to exhibit potent antifouling, antibacterial activity and antifungal activity, with low μM activity against pertinent micro- and macro-fouling organisms and terrestrial bacteria.