Preparation of a Key Intermediate for the Synthesis of the (±)-Pentalenolactone E Methyl Ester by Catalytic ‘Palladium-Ene Cyclization’/Methoxycarbonylation

Bicyclic alcohol (±)- 2 , an advanced intermediate for the synthesis of the methyl ester 1 of pentalenolactone E, has been synthesized in nine operations starting from aldehyde 7 . The key step 6 → 9 is a Pd-catalyzed, tandem intramolecular alkyne allylation/carbonylation reaction.