Abstract
(±)-Evodiakine (1a and 1b), a pair of rearranged rutaecarpine-type alkaloids with an unprecedented 6/5/5/7/6 ring system, were isolated from the nearly ripe fruits of Evodia rutaecarpa. Separation of the enantiomers have been achieved by chiral HPLC column. The structures of (±)-evodiakine were unambiguously elucidated by 1D and 2D NMR spectra, mass spectrometry, and single-crystal X-ray diffraction. Their absolute configurations were determined by comparison of experimental and calculated electronic circular dichroism spectra. A hypothetical biogenetic pathway for (±)-evodiakine was also proposed. Compounds 1a, 1b, and the racemate (1) were tested for their cytotoxic and anti-inflammatory activities.Graphical Electronic supplementary materialThe online version of this article (doi:10.1007/s13659-016-0113-7) contains supplementary material, which is available to authorized users.
Highlights
Abstract (±)-Evodiakine (1a and 1b), a pair of rearranged rutaecarpine-type alkaloids with an unprecedented 6/5/5/7/6 ring system, were isolated from the nearly ripe fruits of Evodia rutaecarpa
Evodia rutaecarpa (Juss.) Benth., a small tree belonging to the family Rutaceae mainly, is distributed in the south regions of Qinling in China [1]
Previous phytochemical study on E. rutaecarpa have focused on rutaecarpine-type alkaloids that produce a number of characteristic compounds with different ring system, including rutaecarpine (6/5/6/6/ 6) [3], evodiagnine (6/5/6/7/6) [4], and wuzhuyurutine A (6/5/5/6/6) [5], as well as several seco-derivatives, such as goshuyuamide I [6] and wuchuyuamide I [7] (Fig. 1)
Summary
Evodiakine (1) was obtained as colorless needles. Its molecular formula C19H17N3O3 was deduced from the HREI-MS at m/z 335.1284 ([M]?, calc. 335.1270), corresponding to 13 degrees of unsaturation. The structure of 1 was identified as a pentacyclic alkaloid by fusing indole and the secopyrroloquinazolone rings [9] (Fig. 3). This confirmed the successful separation of enantiomers, (1)-evodiakine (1a) and (-)-evodiakine (1b). The rings C and D rearrangement of B via attack of the NH in C onto the imine carbon yielded the structure D, which was followed by reduction of the C-5/C-6 double bond to produce compounds 1a and 1b [13, 14]. Ltd.) using various solvent systems and spots were visualized by spraying improved Dragendorff’s reagent to the silica gel plates
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