In the first chapter of this thesis, the macrocyclization of a new type of bifunctional substrates, omega-isocyanoaldehyde derivatives, is described. Ten different omega-isocyanoaldehydes in terms of different ring sizes and functional groups were prepared. They were smoothly proceeded under the simple multicomponent reactions including Passerini reaction, Ugi reaction and modified Ugi reaction. A wide range of 9- to 22-membered macrocyclic lactams were obtained in low to excellent yields with up to four bonds were formed in a single step. In the second chapter, synthetic studies towards the total synthesis of cyclic peptide jamaicensamide A are presented. We applied our strategy to cyclize the advanced intermediate containing omega-isocyanoaldehyde into the cyclic peptide in one-pot procedure. The precursors for the preparation of omega-isocyanoaldehydes with different functional groups and protecting groups were prepared. The derived 24-membered cyclic peptides were formed in good yields. The study on the deprotection of protecting groups is still on-going to complete the total synthesis of jamaicensamide A.