RESIN ACIDS .19. STRUCTURE AND STEREOCHEMISTRY OF ADDUCTS OF LEVOPIMARIC ACID WITH CYCLOPENTENONE AND 1-CYCLOPENTENE-3,5-DIONE . FAVORSKII REACTION OF AN ENEDIONE EPOXIDE

The diene reaction of levopimaric acid (1) with cyclopentenone proceeds in mediocre yield at elevated temperature and affords an endo,cis adduct as major product and an exo,cis adduct in small quantity. The reaction of 1 with 1-cyclopentene-3,5-dione affords a mixture of enolic endo,cis adducts. The structure and stereochemistry of these adducts have been determined by photolytic methods and by correlating them with the product of a novel Favorskii reaction on the epoxide of the known levopimaric acid-benzoquinone adduct. © 1969, American Chemical Society. All rights reserved.