Total Synthesis of (+)-Pestalofone A and (+)-Iso-A82775C

We describe the total synthesis of
epoxyquinoid natural products
(+)-pestalofone A and (+)-iso-A82775C. The synthesis of (+)-16-oxo-iso-A82775C,
the putative biosynthetic precursor of pestalofone C, is also presented.
The allene moiety present in (+)-iso-A82775C and (+)-16-oxo-iso-A82775C
was constructed from the ketodiene-yne group via a biosynthetically
relevant sequence involving a conjugate reduction and a base-catalyzed
tautomerization. Attempted Diels–Alder reaction-based dimerizations
of (+)-16-oxo-iso-A82775C and (+)-iso-A82775C toward pestalofones
B and C are also described.