A state-of-the-art collection of detailed synthetic procedures that lead to a variety of scaffolds, turn mimetics, peptide-bound replacements, and enzyme inhibitors. Topics range from unusual syntheses of amino acids to the use of a variety of linear and heterocyclic scaffolds in place of the peptide backbone. Important chemical procedures and methods include the transient protection of charged peptides as neutral prodrugs for improved blood-brain penetration and the replacement of peptide bonds with heterocyclic rings, olefins and fluoroolefins, and ketomethylenes. Synthetic protocols towards the transition-state mimics and reactive "warheads," applicable in enzyme inhibitors, are also disclosed.