Enantioselective Total Synthesis of (+)-Iso-A82775C, a Proposed Biosynthetic Precursor of Chloropupukeananin

(+)-Iso-A82775C
is a proposed biosynthetic precursor of the chloropupukeananin
family and an important intermediate for related natural products.
The first enantioselective total synthesis of (+)-iso-A82775C (18
steps, 2.2% overall yield) toward the eventual biomimetic total synthesis
of chloropupukeananin is described. The key steps are (1) the enantioselective
Diels–Alder reaction of 4-bromo-3-hydroxy-2-pyrone with methyl
2-chloroacrylate using cinchonine as an organocatalyst and (2) the anti-selective Cu-mediated SN2′ reaction
to afford the axially chiral vinylallene moiety.