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

Abstract

(+)-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 S_N2' reaction to afford the axially chiral vinylallene moiety.