Pd-catalysed C-C macrocyclisation of a simple tripeptide: efficient total synthesis of K-13

The cyclic tripeptide K-13 has been prepared in 11 steps from commercially available starting materials (11% overall yield); the key step is the Pd-ca talysed macrocyclisation of the zinc reagent prepared by selective insertio n of zinc into the aliphatic C-I bond of the linear tripeptide 3, followed by Pd-catalysed macrocyclisation.