Structure and total synthesis of (-)-myrionidine and (-)-schoberine, antimalarial alkaloids from Myrioneuron nutans.

Two new alkaloids, (5S,9S,10R)-myrionidine (1) and (5S,9S,10R,13S)-myrionamide (2), along with the known schoberine (3), were isolated from the leaves of Myrioneuron nutans (Rubiaceae), and their structures were determined from spectral analysis, including mass spectrometry and 2D NMR. The total asymmetric syntheses of (-)-myrionidine (1), (-)-schoberine (3), their enantiomers as well as their 9-epimers derivatives were performed, allowing the determination of their absolute configuration together with that of myrionamide (2). (-)-Myrionidine (1) and its synthetic enantiomer (18) showed a significant antimalarial activity on Plasmodium falciparum.