Synthesis of the steroid skeleton was planned from dehydro-abietic acid (2), a representative resin acid of pine tree. 1. Synthesis of Antipodal Steroids The ketone compounds (4 and 5), important intermediates in synthesis of the skeleton of antipodal steroids, were synthesized via the γ-lactone (7) derived from dehydroabietic acid (2). 2. Synthesis of Steroid A-Ring i) The 3-keto compound (36) having a steroid type A-ring was synthesized by the use of the 4-methyl group in (2) via the keto esters (34 and 35), important intermediates, from the phenacyliden (32) and 1-en ester (33). ii) The phenacyliden (60), obtained via the 4-keto compound (37) derived from dehydroabietic acid (2), was also converted into 3-keto compound (36) 3. Synthesis of Steroid D-Ring i) The C-aromatized steroids (65 and 66) were synthesized by the use of a part or whole of the carbon units of the isopropyl group in dehydroabietic acid (2). ii) The 14-keto compound (69) considered to be an important intermediate in synthesis of steroid skeleton having the 13-methyl group was synthesized via the 14-nitro compound (85) from dehydroabietic acid (2). Synthesis of steroid type D-ring from the 14-keto compound already been completed in the total steroid synthesis.
