Synthesis of IB-01211, a Cyclic Peptide Containing 2,4-Concatenated Thia- and Oxazoles, via Hantzsch Macrocyclization

[structure: see text] An efficient and versatile convergent synthesis of IB-01211 based on a combination of peptide and heterocyclic chemistry is described. The key step in the synthesis is macrocyclization through intramolecular Hantzsch formation of the thiazole ring. Dehydration of a free primary alcohol to furnish the exocyclic methylidene present in the natural product was applied during the macrocyclization.