Total Synthesis and Stereochemistry Revision of Mannopeptimycin Aglycone

Mannopeptimycin is an attractive drug candidate due to its strong antimicrobial activity against drug-resistant strains. However, detailed elucidation of structure-activity relationship and its mode of action has been hampered because the chemical synthesis of the densely functionalized aglycone moiety consisting of cyclic hexapeptide was not established. The key point in the synthesis of the aglycone was the construction of densely functionalized unnatural amino acids, Aiha-A and Aiha-B. This account describes isolation, structural determination of mannopeptimycins, previously reported synthesis of Aiha-A and Aiha-B as well as our short-step, high yielding synthesis of Aihas leading to the first synthesis of mannopeptimycin aglycone with stereo chemistry revision of originally proposed structure.