Studies on the alkaloids from Picrasma quassioides BENNET. V. Structures of picrasidines L,M, and P.
作者:TAICHI OHMOTO、KAZUO KOIKE
DOI:10.1248/cpb.33.3847
日期:——
Two new alkaloids, picrasidines M (II) and P (III), have been isolated from the root-bark of Picrasma quassioides BENNET. The structure of picrasidine L has been revised from 3-methyl-canthin-2, 6-dione to 3-methylcanthin-5, 6-dione (I). The structures were determined on the basis of spectral analysis and chemical evidence.
Three new β-carboline alkaloids, picrasidines I (I), J (II), and K (III), were isolated from the bark of Picrasma quassioides BENNET. The structures were determined on the basis of spectral analyses and chemical transformations.
Picrasidine-U, dimeric alkaloid from Picrasma quassioides
作者:Kazuo Koike、Taichi Ohmoto
DOI:10.1016/0031-9422(88)80725-8
日期:1988.1
Abstract A new canthin-5,6-dione and β-carboline dimericalkaloid, picrasidine-U was isolated from the root wood of Picrasmaquassioides. The structure was determined by spectral analysis and chemical evidence.
Divergent total syntheses of ITHQ-type bis-β-carboline alkaloids by regio-selective formal aza-[4 + 2] cycloaddition and late-stage C–H functionalization
作者:Qixuan Wang、Fusheng Guo、Jin Wang、Xiaoguang Lei
DOI:10.1039/d3sc03722c
日期:——
We herein report the first total syntheses of several bis-β-carboline alkaloids, picrasidines G, S, R, and T, and natural product-like derivatives in a divergent manner. Picrasidines G, S, and T feature an indolotetrahydroquinolizinium (ITHQ) skeleton, while picrasidine R possesses a 1,4-diketone linker between two β-carboline fragments. The synthesis of ITHQ-type bis-β-carboline alkaloids could be
我们在此报告了几种双-β-咔啉生物碱、picrasidines G、S、R 和 T 以及天然产物样衍生物以不同方式的首次全合成。Picrasidines G、S 和 T 具有吲哚四氢喹嗪鎓 (ITHQ) 骨架,而 Picrasidine R 在两个 β-咔啉片段之间具有 1,4-二酮连接体。ITHQ型双-β-咔啉生物碱的合成可以通过乙烯基β-咔啉生物碱的后期区域选择性氮杂-[4+2]环加成直接实现,这表明这种显着的氮杂-[4+2]环加成可能参与生物合成途径。计算研究表明,这种氮杂-[4 + 2]环加成是一个逐步过程,并解释了独特的区域选择性(ΔΔ G = 3.77 kcal mol -1)。此外,铱催化的C-H硼基化在β-咔啉底物上的成功应用使得位点选择性C-8官能化成为可能,从而实现该天然产物家族的高效合成和结构多样化。最后,通过噻唑鎓催化的Stetter反应,完成了picrasidine