Total Synthesis of the Reported Structure of Neaumycin B

The stereoselective total synthesis of structure 1 assigned to the macrolide natural product neaumycin B isreportedin a 2.3% overall yield on 90 mg scale. The synthesis features a gram-scalenickel-catalyzed reductive cross-coupling/spiroketalization tacticto construct the spiroketal core of neaumycin B. The stereostructuresof the C3-C6, C8-C14, and C20-C41 segments ofsynthetic neaumycin B were unambiguously verified by X-ray crystallography.