Lumutinines A-D, linearly fused macroline-macroline and macroline-sarpagine bisindoles from alstonia macrophylla

Four new linearly fused bisindole alkaloids, lumutinines A D (1-4), were isolated from the stem-bark extract of Alstonia macrophylla. Lumutinines A (1) and B (2) represent the first examples of linear, ring A/F-fused macroline-macroline-type bisindoles, while lumutinines C (3) and D (4) were constituted from the union of macroline and sarpagine moieties. A reinvestigation of the stereochemical assignment of alstoumerine (8) by NMR and X-ray diffraction analyses indicated that the configuration at C-16 and C-19 required revision

Oxidized Derivatives of Macroline, Sarpagine, and Pleiocarpamine Alkaloids from <i>Alstonia angustifolia</i>

A total of 20 new indole alkaloids comprising mainly oxidized derivatives of macroline- (including alstofonidine, a macroline indole incorporating a butyrolactone ring-F), pleiocarpamine-, and sarpagine-type alkaloids were isolated from the bark and leaf extracts of <i>Alstonia angustifolia.</i> The structures and relative configurations of these alkaloids were determined using NMR and MS analyses and in some instances confirmed by X-ray diffraction analyses. Alkaloids <b>3</b>, <b>7</b>, <b>35</b>, and <b>41</b> showed moderate to weak activity, while <b>21</b> showed strong activity in reversing multidrug resistance in vincristine-resistant KB cells

Oxidized Derivatives of Macroline, Sarpagine, and Pleiocarpamine Alkaloids from <i>Alstonia angustifolia</i>

A total of 20 new indole alkaloids comprising mainly oxidized derivatives of macroline- (including alstofonidine, a macroline indole incorporating a butyrolactone ring-F), pleiocarpamine-, and sarpagine-type alkaloids were isolated from the bark and leaf extracts of <i>Alstonia angustifolia.</i> The structures and relative configurations of these alkaloids were determined using NMR and MS analyses and in some instances confirmed by X-ray diffraction analyses. Alkaloids <b>3</b>, <b>7</b>, <b>35</b>, and <b>41</b> showed moderate to weak activity, while <b>21</b> showed strong activity in reversing multidrug resistance in vincristine-resistant KB cells

Oxidized Derivatives of Macroline, Sarpagine, and Pleiocarpamine Alkaloids from <i>Alstonia angustifolia</i>

A total of 20 new indole alkaloids comprising mainly oxidized derivatives of macroline- (including alstofonidine, a macroline indole incorporating a butyrolactone ring-F), pleiocarpamine-, and sarpagine-type alkaloids were isolated from the bark and leaf extracts of <i>Alstonia angustifolia.</i> The structures and relative configurations of these alkaloids were determined using NMR and MS analyses and in some instances confirmed by X-ray diffraction analyses. Alkaloids <b>3</b>, <b>7</b>, <b>35</b>, and <b>41</b> showed moderate to weak activity, while <b>21</b> showed strong activity in reversing multidrug resistance in vincristine-resistant KB cells

Perhentidines A–C: Macroline–Macroline Bisindoles from <i>Alstonia</i> and the Absolute Configuration of Perhentinine and Macralstonine

Three new bisindole alkaloids of the macroline–macroline type, perhentidines A–C (<b>1</b>–<b>3</b>), were isolated from the stem-bark extract of <i>Alstonia macrophylla</i> and <i>Alstonia angustifolia</i>. The structures of these alkaloids were established on the basis of NMR and MS analyses. The absolute configurations of perhentinine (<b>4</b>) and macralstonine (<b>5</b>) were established by X-ray diffraction analyses, which facilitated assignment of the configuration at C-20 in the regioisomeric bisindole alkaloids perhentidines A–C (<b>1</b>–<b>3</b>). A potentially useful method for the determination of the configuration at C-20 based on comparison of the NMR chemical shifts of the bisindoles and their acetate derivatives, in these and related bisindoles with similar constitution and branching of the monomeric units, is also presented