Vobasonidine and Vobatricine, Novel Bisindole Alkaloids from a Malayan Tabernaemontana

Abstract

Two novel bisindole alkaloids of the vobasine-vobasine and vobasine-strychnan type, viz., vobasonidine (2) and vobatricine (3) were obtained from the leaf and stembark extracts, respectively, of the Malayan species Tabernaemontana corymbosa, and their structures were established by spectroscopic analysis.

Conoliferine and isoconoliferine, structurally novel alkaloid-lignan conjugates from Tabernaemontana corymbosa

“…The Malayan T. corymbosa for instance has provided several new alkaloids that are characterized by novel molecular skeletons such as the hexacyclic alkaloid, tronoharine, 5 the pentacyclic indole, tronocarpine 6 and the indole-derived quinolinic alkaloid, voastrictine. 7 The same plant also yielded a number of new indole and bisindole alkaloids, [8][9][10][11][12][13][14][15][16][17] including several vobasinyl-iboga bisindoles, which reverse multidrug-resistance in vincristine-resistant KB cells. 8 We recently reported the structure of conolutinine, a hexacyclic indole characterized by a novel ring system incorporating a diazaspirocenter and fused oxadiazepine-tetrahydrofuran rings, which was isolated from a different sample of T. corymbosa.…”

Structure, biological activity, and a biomimetic partial synthesis of the lirofolines, novel pentacylic indole alkaloids from Tabernaemontana

“…The attachment of the 2-aza-6-ethylbicyclo[2.2.2]octane fragment was deduced to be from C(2) to C (16), which is unchanged from that in an iboga skeleton. This was clearly indicated by the observed correlations from H (16) and H (17) to C (2) in the HMBC spectrum (Fig. 1).…”

“…10 The Malayan representatives of this genus are also notable for producing new indole and bisindole alkaloids, including a number which exhibited important biological activities. [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] We now report the isolation and structure elucidation of two new pentacyclic indole alkaloids, lirofolines A (1) and B (2), from the stem-bark extracts of T. corymbosa and T. divaricata, respectively. 27 .…”

Conodirinines A and B, Novel Vobasine‐Iboga Bisindoles Incorporating an Additional Tetrahydro‐1,3‐oxazine Unit on the Vobasinyl Moiety

“…These plants are notable for producing a wide variety of indole and bisindole alkaloids, including many with intriguing C-skeletons as well as novel biological activities [2] [3]. ex Wall [5 ± 10], including conodiparine A (1), a new vobasine-iboga bisindole, which was found to reverse multidrug-resistance (MDR) in vincristine-resistant KB cells [9], and vobatricine (2), representing the first example of a bisindole of the vobasine-strychnan type [10]. We have previously reported the structures of several new indole and bisindole alkaloids that possess novel C-skeletons from the Malayan species, T. corymbosa Roxb.…”