Alstonlarsines A–D, Four Rearranged Indole Alkaloids from Alstonia scholaris

Four indole alkaloids, alstonlarsines A–D (1–4), were isolated from Alstonia scholarisand structurally characterized. Compound 1possesses a new carbon skeleton with a cage-shaped 9-azatricyclo[4.3.1.03,8]decane motif, and compounds 2–4feature a rare carbon skeleton that was found in nature for the first time. Plausible biosynthetic routes for 1–4are proposed. Compound 1showed DRAK2 inhibitory activity with an IC50value of 11.65 ± 0.63 μΜ.