Cyclic peptide libraries of novel compounds serve as valuable collections for researchers to mine for new therapeutics. The proposed methods for creating cyclic peptide libraries utilize biosynthetic pathways from various organisms. The enzymatic steps are broken into individual components and then reassembled in unique ways to generate large collections of novel chemical entities (NCEs).

One method uses amide-linked peptides created in vivo by expression of constructs in E. coli. Another method centers on prenylated compounds created from marine ascidian enzymes, again expressed in E. coli. The final method utilizes natural pathways from sponges to synthesize compounds for libraries. Methods to increase the yield and potency of peptides, specifically cyanobactin and prenylated peptides, in the libraries have also been developed.