Synthesis of Microphyllaquinone

Significance

Extracts of the roots from Lippia microphylla have long been used in Brazilian traditional medicine as expectorants, astringents and diuretics. Naphthoquinone dimer microphylla­quinone has recently been identified as one of the active components and it displays cytotoxic activity. Noteworthy in this synthesis is (1) the conjugate addition of functionalized organocopper ­reagent E to D and (2) the biomimetic oxa 6π-electrocyclization of putative ortho-quinone methide H to form the central pyran ring.