Our aim is to find new antibacterial molecules with novel mechanisms of action, by applying new and innovative approaches in organic and medicinal chemistry, such as diversity-oriented synthesis (DOS) and chemical genetics. The concrete objectives are: -Development of diversity-oriented synthesis (DOS) using solid phase and solution synthesis to obtain collections of highly diverse and complex small cyclic peptide derivatives including small cyclic di- tri- and tetra- peptides as well as bicyclic diketopiperazines (DKP's). -Development of new methodologies for solid phase organic synthesis: optimization of relatively new reactions such as RCM or enyne metathesis on solid phase. -Biological screening of the molecular libraries on cultures of human pathogen bacteria and selection of the most active compounds to identify new modes of antibacterial action. This project addresses major challenges in both therapeutics and organic synthesis, such as bacterial resistance to existing drugs, development of new methodologies for solid phase organic synthesis and diversity-oriented synthesis and chemical genetics in Europe. It is a multidisciplinary project that involves a highly valuable education for the candidate in new scientific aspects related to his research field.