Steroselective total syntheses of diterpene resin acids

A stereoselective total synthesis of ([plus-minus])-callitrisic acid (1) from p-isopropenyliospropylbenzene via intermediate keto-ester 59, as well as a stereoselective total synthesis of ([plus-minus])-podocarpic acid (.2) from enone 63 via intermediate keto-ester 64 are described. The synthetic approach involves a new and highly stereoselective reductive-elimination-alkylation reaction on vinyl ether esters 61 and 65, respectively. Lithium in liquid-ammonia followed by methyl iodide was used for the simultaneous reduction, deoxygenation, and stereoselective alkylation in single step.