β-amino acids are key structural elements of peptides, peptidomimetics and many other physiologically active compounds. Notably, b-amino acids are precursors for b-lactams, the most important class of antibiotics. Although some b-amino acids themselves show interesting pharmacological properties, usually they are intermediates en route to more complex products with biological and pharmacological activity. In recent years, it has become clear that peptides based on β-amino acids have secondary structures comparable to their a-amino acid analogues, but are not vulnerable towards proteases.