Prenylation is a universal covalent post-translational modification found in all eukaryotic cells, comprising attachment of either a farnesyl or a geranylgeranyl isoprenoid. Prenyl group is important for protein-protein binding through specialized prenyl-binding domains. Farnesylation and geranyl geranylation are very important in C-terminal anchoring of proteins to the cell membrane. These post-translational modification are most often catalyzed by either protein farnesyl transferase (FTase) or protein geranyl geranyl transferase-I (GGTase-I). These enzymes typically recognize a CaaX motif, where “C” is the cysteine to be prenylated and the remainder of the motif leads to recognition by FTase and/or GGTase-I. Prenylation plays vital role in diversification of natural products flavonoids, coumarins, and isoflavonoids. Many prenylated compounds have been identified as active components in medicinal plants with biological activities, such as anti-cancer, anti-spasmodic, anti-bacterial, anti-fungal, anti-inflammatory, and anti-androgen activity. Due to their beneficial effects on diseases, prenylated compounds are of particular interest as lead compounds for producing drugs and functional foods. In this chapter, we concise the prenylation reactions of aromatic compounds such as indole, ketones, and aldehydes that may results to lead molecules discovery. Prenylation reactions are applied on azoles, anilines, thioles, indole, α-carbonyl bromides, and aryl bromide. There are several drugs that are obtained from prenylation, i.e. (-)-17-hydroxy-citrinalin, (+)-stephacidin, prenylated. In this text there is no referencing, it is a chemical name, so keep as it is.