Studies on the Terpenoids and Related Alicyclic Compounds. XXI. Formation and X-Ray Crystal Structure of a Novel Spiro Dimer of 6-Dehydroxysantoninic Acid

Abstract

Treatment of 14-bromo-6-dehydroxysantoninic acid (1a) with 10% Na₂CO₃-acetone solution gave the lactone dimer (2), the spiro dimer (5), and a hydroxy compound (4), in 17%, 40%, and 21% yields, respectively. The molecular structure of the major product, 6-dehydroxysantoninic acid spiro dimer (5), was confirmed by X-ray crystallographic analysis. The mechanism of formation of 5 during the course of this reaction is discussed.