Stereoselective Partial Synthesis of (+)-Pisiferic Acid

(+)-Pisiferic acid ( 1 ), an antibiotic active against Gram-negative and Gram-positive bacteria, was synthesized starting from dehydroabietic acid ( 2 ) or abietic acid ( 26 ). The terpene ring system was functionalized and a Barton reaction used to oxidize Me(20). The intermediates of this photochemical reaction were isolated and characterized.