Strategy for the synthesis of large peptides: An application to the total synthesis of human parathyroid hormone [hPTH(1–84)]

A strategy suitable for the synthesis of larger peptides is proposed. It involves the following four considerations: (1) all of the side‐chain functional groups are protected by benzyl‐type protective groups; (2) a water‐soluble carbodiimide, 1‐ethyl‐3‐(3‐dimethylaminopropyl)‐carbodiimide, is used for the fragment‐condensation reactions together with 1‐hydroxybenzotriazole as the additive; (3) all the protective groups are cleaved simultaneously by the HF method in the final stage of the synthesis; and (4) side products formed are detected and removed by an efficient high‐performance liquid chromatography procedure. The usefulness of these procedures is demonstrated taking the synthesis of human parathyroid hormone [hPTH(1–84)] as an example.