Migration of the exocyclic double bond in terpenoid coumarins of the iresane series

In terpenoid coumarins of the iresane series with an exocyclic double bond, migration of the double bond into the ring with the retention of the configuration of the substituent in position 1 is observed in an acid medium. The reaction has been performed in CF₃COOH and has been monitored by the PMR method. Badrakemin has yielded conferol, badrakemone has yielded conferone, badrakemin acetate has yielded conferol acetate, colladonin has yielded moschatol, and farnesiferol A and gummosin have yielded the corresponding isomers with endocyclic double bonds. The rate of the reaction is affected by the nature of the substituent at C-6. The presence of a keto group increases the time of isomerization to 1.5 h as compared with the 5–10 min for compounds with an OH group at C-6. The increase in the time of the reaction leads to the formation of byproducts. The reaction does not take place in CH₃COOH.All-Union Scientific-Research Institute of Medicinal Plants, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 630–637, September–October, 1979.