The alkaloids of Margaritaria indica. Part 2. The structures of 4-epiphyllanthine, margaritarine and the structural revision of securinol A

Extraction of the bark of Margaritaria indica has yielded the new alkaloids (4α)-4-methoxysecurinan-11-one 3 and 3-{N-[(2α,15α)-14,15-dihydro-11-oxosecurinan-15-yl]-2-aminoethyl}-1H-indole 10. Their structures followed from their spectroscopic properties. High field NMR spectra for the known Securinega alkaloids (4β)-4-methoxysecurinan-11-one 2 and (2α,4α)-4-methoxysecurinan-11-one 5 were recorded and interpreted. The structure of the known alkaloid securinol A is revised to 17 as a result of an X-ray crystal structure determination of its hydrobromide.