Regioselective Synthesis of 14-Membered Biaryl Ethers: Total Synthesis of RA-VII and Deoxybouvardin.
作者:Tsutomu INOUE、Takashi INABA、Isao UMEZAWA、Masayuki YUASA、Hideji ITOKAWA、Katsuyuki OGURA、Katsuichiro KOMATSU、Hiroshi HARA、Osamu HOSHINO
DOI:10.1248/cpb.43.1325
日期:——
In order to obtain a key compound (22a") for synthesis of RA-VII (1) and deoxybouvardin (2), construction of the 14-membered ring system was performed by means of thallium trinitrate-mediated oxidation of the tetrahalogeno amides 5-7. The dibromo dichloro amide 6 or the bromo trichloro amide 7 gave a natural type of 14-membered ring dienone (23a or 23c), whereas the tetrabromo amide 5 gave an unnatural type of product, 19a. The formation of the latter product 19a could be understood on the basis of energy calculations on plausible intermediates 26a-c and 27a-c in the transition state in the oxidaive coupling reaction. Compound 23a was further converted to 22a" through conventional procedures (aromatization; methylation; catalytic hydrogenation). This intermediate was readily converted to 1 and 2. Thus, total synthesis of RA-VII (1) and deoxybouvardin (2) was achieved for the first time.
为了获得合成RA-VII(1)和去氧布瓦丁(2)的关键化合物(22a"),通过三硝酸铋介导的氧化反应对四卤酰胺5-7构建了14元环体系。二溴二氯酰胺6或溴三氯酰胺7产生了一种天然类型的14元环二烯酮(23a或23c),而四溴酰胺5则产生了一种非自然的产物19a。产物19a的形成可以通过对氧化偶联反应中可能的过渡态中间体26a-c和27a-c进行能量计算来理解。化合物23a通过常规程序(芳构化;甲基化;催化氢化)进一步转化为22a"。该中间体可以很方便地转化为1和2。因此,RA-VII(1)和去氧布瓦丁(2)的总合成首次得以实现。