Diterpenes. Part XI. Iodocarboxylations of phyllocladene (8β,13β-kaur-16-ene) and isophyllocladene (8β,13β-kaur-15-ene)

Abstract

16-Acetoxy-17-iodo-(15) and 17-acetoxy-16-hydroxy-8β,13β-kaurane (16) have been isolated from the reaction of phyllocladene (8β,13β-kaur-16-ene)(1) with thallium(I) acetate–iodine, and 17-iodo-8β,13β-kaur-15-ene (10) has been obtained from the reaction with thallium(I) tosylate. Treatment of phyllocladene or isophyllocladene (8β,13β-kaur-15-ene)(6) with thallium(I) benzoate–iodine gives 8β,13β-kaur-15-en-17-yl benzoate (7) and 8β,13β-kaur-16-en-15α-yl benzoate (2), which are also obtained using silver benzoate–iodine. Formation of the products is discussed and an S_N2′ type mechanism is proposed for the solvolysis of the allylic iodide (10) with thallium(I) acetate.