A Chemoenzymatic and Fully Stereocontrolled Total Synthesis of the Antibacterial Natural Product (-)-Platencin

The natural product (-)-platencin is a potent antibacterial agent that exerts its effects through a novel mode of action. As such, it is an important lead in the development of next-generation antibacterials that are urgently needed because of the rapidly developing resistance to current therapies. The work reported here concerns the development of a convergent and chemoenzymatic total synthesis of (-platencin by methods that should provide access to a range of biologically relevant analogues. The key step involves a thermally promoted and facially selective intramolecular Diels-Alder (IMDA) cycloaddition reaction to give an adduct that embodies the tricarbocyclic core of (-)-platencin. This adduct was elaborated over thirteen steps to the natural product. The substrate for the IMDA reaction was prepared by Stille cross-coupling of a Z-configured alkenylstannane with an iodinated diene obtained in an enantiomerically pure form through the whole-cell biotransformation of iodobenzene.