Synthesis of (±)-pyrenolide B

Article abstract of DOI:10.1002/hlca.19950780313

In the synthesis of the title compound 12, the important intermediate 7 was obtained in good yield from the easily available ethyl 5,5-ethylenedioxy-2-oxocyclohexane-1-carboxylate (1) via ring enlargement of the bicyclic enol ether 5. Its reduction (NaBH₄, CeCl₃ in EtOH) and subsequent protection with (t-Bu)Me₂Si resulted in the highly functionalized ten-membered lactone 9. Introduction of the (Z)-configurated double bond, followed by deprotection and elimination of H₂O, gave (±)-pyrenolide B (12) in 16% overall yield.