Introduction to Unnatural Foldamers

This chapter describes some recent and typical examples of synthetic foldamers. The foldamers are divided into into two large families: biotic foldamers and abiotic foldamers. First, the chapter discusses some examples of biotic foldamers containing unusual amino acids or unusual functions that replace the amide moiety. The examples presented are β-peptides, β-peptides, hybrid foldamers, aliphatic urea foldamers, foldamers of α-aminoxy acids, and foldamers containing amido groups. Then, the chapter talks about abiotic foldamers. Another interesting topic is the study of the driving force for the folding of foldamers with heterogeneous backbones. Some of these compounds tend to be self-organized, while others assume secondary structures only when they are in contact with external agents such as solvents, anions or metals. The chapter shows some examples of foldamer organization driven by external agents. Finally, it reports some examples of foldamer applications for the formation of pharmacologically active compounds and discrete tertiary structures.