The course will provide the essential tools for the retrosynthetic analysis of any organic molecule, with a detailed analysis of the various disconnections (from monofunctional molecules to more complex ones, even including stereochemical aspects), the functional group interconversion (deepening the knowledge of the reactivity dealt in Organic Chemistry I and II), the use of protecting groups strategy. Particular attention will be given to the planning of an efficient synthesis in terms of yield (linear synthesis vs. convergent or multicomponent) and atom economy. During the course several examples will be examined in parallel to the given notions, with a particular attention to the retrosynthesis and synthesis of bioactive organic molecules. Laboratory lessons will be focused on a multistep synthesis, the isolation of the products and their spectroscopic characterization.