Synthetic Circularized Analogues of Bovine Pancreatic Trypsin Inhibitor

Two cyclic analogues of the protein bovine pancreatic trypsin inhibitor (BPTI), c-[R]Smc and c-Cys5[R]Abu, have been synthesized. For the first target, a semisynthetic approach featured a cyclization that took advantage of the constraint imposed by the three disulfides of the native protein. For the second target, an entirely unstructured 58-residue thiolester, prepared by total synthesis with mild Fmoc chemistry and a side-chain anchoring strategy, was cyclized by native chemical ligation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)