N-(tert-Butoxycarbonyl)-L-proline is widely used as a building block in solution-phase and solid-phase peptide synthesis for the preparation of peptides peptide-based pharmaceuticals and other research compounds.

Its purpose is to protect the amino group of L-proline during peptide synthesis allowing controlled peptide bond formation and reducing unwanted side reactions.

N-(tert-Butoxycarbonyl)-L-proline (Boc-L-proline or Boc-Pro-OH) is the Boc-protected derivative of the amino acid L-proline in which the amino group is protected with a tert-butoxycarbonyl (Boc) group while the carboxyl group remains free.