Stereoselective intramolecular 6-exo-Heck reaction : A facile synthetic route to podocarpa-8,11,13-triene and diterpenoid resin acids intermediates
Intramolecular Heck reaction of the olefins 1a-c in the presence of sodium formate affords ca 3:1 mixtures of the respective trans- and cis-octahydrophenanthrenes 3a-c and 4a-c. Similar reaction of the olefmic ester 2 provides a 70:30 mixture of (±)-methyl desisopropyldehydroabietate 6 and (±)10-epi-methyl desoxypodocarpate 7.