Obovamine, a New Indole Alkaloid fromStemmadenia obovata

Abstract

The stem bark of the Panamanian plant Stemmademia obovata has afforded a new ibogainetype alkaloid, obovamine (1), whose structure was determined by a combination of spectral interpretation and chemical correlations. Ten known alkaloids, coronaridine, coronaridine hydroxyindolenine, voacangine, voacangine hydroxyindolenine, (19S)-heyneanine, (19S)-heyneanine hydroxyindolenine, (19S)-voacristine, (19S)-voacristine hydroxyindolenine, ajmalicine, and ajmalicinine, were also isolated. Voacangine was the main alkaloid constituent.In a previous work, we reported the isolation of obovatine, bis[11-hydroxycoronaridin-12-yl]-11-hydroxycoronaridine, and voacristine from the leaves 1 and N 1 -methyl-11-hydroxymacusine A from the stem bark 2 of Stemmadenia obovata. Here we report the study of the organic-soluble stem bark fraction. The acidic and neutral crude alkaloidal fractions of the EtOH extract afforded the new iboga indolenine alkaloid obovamine (1) and the known alkaloids voacangine 3 (2), voacangine hydroxyindolenine 4 (3), coronaridine, 5 coronaridine hydroxyindolenine 6 (4), (19S)-heyneanine, 7 (19S)-heyneanine hydroxyindolenine, 8 (19S)-voacristine, 7 (19S)-voacristine hydroxyindolenine, 9 ajmalicine 10 (5), and an epimeric mixture of ajmalicinine 11 (6) and 17-epi-ajmalicinine (7). The known compounds were identified by comparison of their spectral data with those reported in the literature. Results and DiscussionObovamine (1), a minor alkaloid, was isolated as an amorphous compound by a combination of adsorption column chromatography and preparative TLC. The UV maxima at 224 and 286 shown by 1 are similar to those of a 10-methoxy-7-hydroxyindolenine chromophore. 4 The IR spectrum showed an absorption band belonging to a carbonyl ester (1731 cm -1 ) and strong bands (1155, 1090 cm -1 ) attributable to an ether functionalization. The mass spectrum displayed a molecular ion at m/z 382, two amu less than for voacangine hydroxyindolenine (3), and the fragments at m/z 367, [M -15] + 353, [M -29] + , and 323 [M -59] + corresponding to the loss of an ethyl side chain and a carbomethoxy group, respectively.

Indole alkaloids from Ervatamia flabellformia

“…The spectroscopic data of all compounds were in good agreement with the literature data [4][5][6][7][8][9][10][11][12][13][14]. All these structures are isolated from E. flabellformia for the first time.…”

Absolute Configuration of Alkaloids from Uncaria longiflora through Experimental and Computational Approaches

“…The hydroxy group was proposed to be β-oriented by comparison with the chemical shifts observed for ring E with those of ajmalicinine, a POA with a hydroxy group at C-17. 20 Comparison of the 1 H NMR shifts observed for the H-17β equatorial and H-17α axial protons in the H-17 anomers allowed for the assignment of H-17 in alkaloid 1 as axial (J 16,17 = 8.7 Hz). An equatorial proton would cause H-17 to appear more downfield and show J = 3.5 Hz with H-16.…”

Monoterpenoid Indole Alkaloids from Catharanthus roseus Cultivated in Yunnan

“…C. roseus has also been cultivated widely in China as an outside ornamental, which inspired us to search for structurally diverse indole alkaloids from the same plant in different ecological environments. Phytochemical investigation of the alkaloids of C. roseus cultivated in Xishuangbanna, a tropical rainforest zone, afforded a new alkaloid 15,20-dehydro-3-(2-oxopropyl) coronaridine (1), along with sixteen analogues (2-17), coronaridine (2) [3], tetrahydroalstonine (3) [4], ajmalicine (4) [4], ajmalicinine (5) [5], serpentine (6) [6], 19-epi-alstonine (7) [7], yohimbine (8) [8], 19,20-dehydro-16-epi-yohimbine (9) [9], 16R-sitsirikine (10) [10], isositsirikine (11) [10], 16R-dihydrositsirikine (12) [11], pericyclivine (13) [12], akuammidine (14) [12], 17-acetyllochnerine (15) [13], 21-carbonylnormavacurine (16) [14], and 19S-epimisiline (17) [15]. Among them, alkaloid (16) was isolated from this plant for the first time.…”