Focus Synthesis is a new research chemical supplier that uses rational principles based in chemoinformatics in the design of chemical building blocks that are ideally suited for DOS (diversity-oriented synthesis). Focus Synthesis products include members of unique and underrepresented substructure classes, building blocks designed for thorough chemical space coverage, exotic heterocycles and precursors for highly focused combinatorial libraries. The mission of Focus Synthesis is to provide tool sets for discovering the drugs of the future by optimizing diversity and enabling comprehensive single-site and isosteric changes in biologically active small molecules that result in optimal SAR knowledge.