19 Bufadienolideの過酸化水素とTris(acetyl acetonate)Iron(III)によるエポキシ化反応

概要

論文の詳細を見る
Epoxidation reactions of bufadienolides with hydrogen peroxide and tris (acetyl acetonate) Iron (III) were studied, since the peracids such as m-chloroperbenzoic acid do not attack the 2-pyrone ring double bonds but hydrogen peroxide-tris (acetyl acetonate) Iron (III) was found to give a 20,21ξ-epoxyderivative. With 14-dehydrobufalin (1), the reaction gave 2-pyrone epoxide 3 as an intermediate that was transformed into 14,15α;20,21ξ-diepoxide 4. The diepoxide (4) was also obtained in the same manner from 14,-15α-epoxybufalin(2). Epoxidation of the 2-pyrone ring system was more smooth than that of steroidal 14-olefin. The similar reaction provided the bufadienolide 2-pyrone epoxides, 6, 8, 13 and 14, respectively. Although bufalin (9) gave 20,21-epoxide 10 by the same method, 2-pyrone epoxide 10 was found to isomerize slowly with contact on silica gel to give cyclic ethers, 11 and 12. The isomerization reaction suggests that the 14β-hydroxy group is located near the 21- and 22-carbon position. As another reaction, epoxidation of the 14,21-epoxy-20(21),22-dienoate(15) provided the two compounds, 16 and 17, respectively.
天然有機化合物討論会の論文
1980-09-10