Synthesis of the unique angular tricyclic chromone structure proposed for aspergillitine, and its relationship with alkaloid TMC-120B

Abstract

The synthesis of the tricyclic angular chromone structure originally assigned to aspergillitine is reported. The synthesis was achieved in 11 steps and 15% overall yield from 2,4-dihydroxypropiophenone, through the intermediacy of 2,3-dimethyl-7-hydroxychromen-4-one. Construction of the nitrogen-bearing heterocyclic ring entailed a Stille cross-coupling reaction with n-Bu₃SnCH₂CHCH₂, followed by double bond isomerization, oximation of the chromone carbonyl, and a final microwave-assisted electrocyclization of the thus formed 6π-electron aza-triene system.