Natural compounds isolated from terrestrial plants have been studied for a long time and have been successful. However, studies on marine compounds have only begun in the middle of the last century. Currently, natural marine compounds are known to be a promising source of pharmaceuticals, and many highly biologically active compounds have been found in various marine organisms. Difficulties in collecting large amounts of samples and requiring high funding are one of the obstacles to research in the field of marine chemical compounds. Therefore, organic synthesis is an effective alternative to generate larger amounts of active ingredients to serve biological studies, as well as to ensure their applicability. Many marine-derived active compounds play as lead compounds so that researchers can make new derivatives possess higher biological activity. The bengamides isolated from marine sponges are known for their potent anti-cancer activity. However, structural instability is one of the reasons limiting the applicability of this class. In order to overcome this limitation of bengamides, we chose the research topic “Synthesis and cytotoxicity of bengamide analogues A and E” in this thesis.