Diterpenoids. XXXVIII. Conversion of l-abietic acid into steroidal skeletons: Formation of the D-ring. I.
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The steroidal D-rings (31 and 37), along with 32 and 38, were synthesized by the use of a part or whole of the carbon units of the isopropyl group of l-abietic acid (1), via oxidation of 18 or 20 with Tl (ONO<SUB>2</SUB>)<SUB>3</SUB>, or addition reaction of 20 with 1, 1-dichloroethylene, and modifications of the functionality, followed by Friedel-Crafts cyclization. Cyclization to the 14-position (formation of 31 or 37) in 30 or 35 was always predominant over that to the 12-position (formation of 32 or 38). In attempts for functionalization of the isopropyl group with Pb (OAc)<SUB>4</SUB>, 9, a hopeful intermediate to syntheseze quinoid diterpenes, was obtained via 3, 4, 5 and 6. RuO<SUB>2</SUB> reduction of 6 and successive Pb (OAc)<SUB>4</SUB> oxidation to 17 is also described.
- Chemical and Pharmaceutical Bulletin
Chemical and Pharmaceutical Bulletin 23(12), 3189-3202, 1975
The Pharmaceutical Society of Japan