Ring-Closing Enyne Metathesis Approach to Functionalized Semicyclic Dienes: The Total Synthesis of (–)-Tetrangomycin

摘要

The angucycline antibiotic (–)-tetrangomycin was synthesized in 13 steps (11% overall yield) by using a stereoselective Diels–Alder reaction between a naphthoquinone and a semicyclic diene to construct the benz[a]anthraquinone ring system. The diene intermediates were synthesized through a ring-closing enyne metathesis reaction. The tertiary alcoholat C-3 was installed by an asymmetric dihydroxylation reaction. The relative stereochemistry of the dienes was verified by the NMR analyses of the cycloadducts that were obtained from their reaction with N-phenylmaleimide. Selective aromatization of the B ring was achieved under oxidative conditions.