Small organic molecules are compounds that are manufactured through chemical synthesis. One of the key advantages of small molecules is that they have a low molecular weight and simple chemical structures. This allows more predictability to their pharmacokinetics and pharmacodynamics, which means that dosing is simpler. To use small molecules as a useful tool to address human health issues, the collaboration between disciplines, especially chemistry and biology, is essential. In recent years in our laboratories, we have demonstrated that climacostol, a 5-alkenyl resorcinolic produced by eukaryotic microorganisms as secondary metabolite and obtained by our synthetic strategy too, it shows important biological and pharmacological activities. These ones are highly dependent on the 5-alkenyl chain, and chemical modifications to the resorcinolic moiety can be exploited to achieve higher toxicity against pathogen microbes and protists than climacostol. In this study, we have designed and made a synthetic strategy for a new analogue of climacostol (AN3), and evaluated how the new hydroxyl group at position four in the aromatic ring influences its biological effects on prokaryotic and free-living protists and on non-target cells/organisms, especially with regard to cytotoxic properties.