Development of a synthetic route to the oxaphenalenone (OP) natural products neonectrolides BE is described. The synthesis relies on gold-catalyzed 6-endo-dig hydroarylation of an unusual enynol substrate as well as a one-pot Rieche formylation/cyclization/deprotection sequence to efficiently construct the tricyclic oxaphenalenone framework in the form of a masked orthoquinone methide (o-QM). A tandem cycloisomerization/[4+2] cycloaddition strategy was employed to quickly construct molecules resembling the neonectrolides. The tricyclic OP natural product SF226 could be converted to corymbiferan lactone E and a related masked o-QM. Our study culminates with the application of the tandem reaction sequence to syntheses of neonectrolides BE as well as previously unreported exo-diastereomers.
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