Total Synthesis of (±)‐2‐Pupukeanone

(±)‐2‐Pupukenone ( 4 ) has been synthesized, the key step being the intramolcular Diels‐Alder reaction of the intermediate 13 to 14 (42%) and 15 (14%). The bromodiene 12 has been obtained from the reaction of α‐isopropylidene‐γ‐lactone ( Scheme 2 ) 12 with sodium phenylselenide and subsequent esterification to 9 , oxidation and thermal elimination of which furnished 10 . Reduction of 10 with diisobutylaluminimum hydride and treatment of the resulting alcohol 11 with PBr 3 led to the required bromodiene 12 . Finally, hydrogenation of the 14 on Pt(C) in CH 3 OH gave a 4:1 mixture of 2‐pupukeanone ( 4 ) and epi‐2‐pupukeanone 16 .