Anionic [4+2] cycloaddition strategy in the regiospecific synthesis of carbazoles: formal synthesis of ellipticine and murrayaquinone A

Total Synthesis of Carbazole Alkaloid Murrayaquinone A

“…如 Scheme 1 所示, 以 3-乙酰基吲哚 7 [19] 193.0, 137.0, 135.8, 135.0, 129.0, 128.2, 126.9, 126.4, 123.4, 122.6, 122.6, 117.4, 110.1, 50.7, 27.6 3, 168.5, 137.1, 135.8, 135.5, 129.1, 128.3, 127.0, 126.5, 123.9, 123.1, 122.7, 116.4, 110.3, 52.4 3.18 (dd,J＝14.7,7.2 Hz,1H),3.13 (dd,J＝14.7,7.0 Hz, 1H); 13 C NMR (100 MHz, CDCl 3 ) δ: 187. 3, 169.5, 137.1, 136.2, 135.3, 130.2, 129.0, 128.3, 127.1, 126.6, 123.9, 123.2, 122.8, 119.9, 116.1, 110.3, 53.7, 52.5, 50.9, 40.7; IR (neat) ν max : 1739, 1645, 1526, 1386, 1186 cm -1 ; HRMS (ESI) calcd for C 22 H 20 NNaO 3 [M＋Na] ＋ 448.0519, found 448.0511.…”

“…目前已有多个课题组报道了 Murrayaquinone A 的全合成, 根据合成过程中最后一个环的构建, 可以分 为吡咯 B 环的构建, 以及苯醌 A 环的构建两种策略. 其 中, 绝大多数报道都是采用构建吡咯 B 环的策略, 包括 过渡金属催化的二苯胺衍生物的偶联 [9] 、2-氨基醌和苯 炔或环己烯酮的成环反应 [10] 以及 2-硝基苯乙烯衍生物 的还原环化 [11] 等; 而以包含 B、C 环的吲哚衍生物为底 物来构建 A 环的报道较少, 主要有烯烃复分解 [12] 、[4＋ 2]环加成 [13] 等方法. 此外, 也有对已有咔唑环进行修饰 从而合成 Murrayaquinone A 的报道 [14] .…”

Isolation, biological activity and synthesis of the natural product ellipticine and related pyridocarbazoles

“…Mal et al devised an anionic [4+2] cycloaddition strategy towards the ellipticine quinone and related carbazole quinones. 121,122 Indolofuranone 163 was treated with triethylamine and ethylchloroformate to give the N-ethoxycarbonyl derivative 164 in 92% yield (Scheme 32). Reaction of 164 with 3,4-pyridyne (prepared in situ from 3-bromopyridine) in the presence of lithium diisopropylamide gave an inseparable mixture of the ellipticine and isoellipticine quinones 70 & 76 (45%).…”

Total Synthesis of Carbazole Alkaloids – Ekeberginine, Harmandianamine A, and Furanoclausamine B

“…Among the known synthetic approaches, we have been particularly interested in the anionic [4+2] annulation10 strategy because of its regiochemical integrity. We recently accomplished the total synthesis of clausevatine D10b ( 7 ) adopting this strategy 10c,11…”