Stereoselective Total Syntheses of C18-Oxo Eburnamine-Vincamine Alkaloids.

Here, we disclose the divergent total syntheses of representative C18-oxo eburnamine-vincamine alkaloids (+)-eburnaminol, (-)-larutenine, and (-)-cuanzine. Key to the approach is a substrate-controlled iridium-catalyzed asymmetric hydrogenation/lactamization cascade that leads to the formation of the common tetracyclic skeleton with essential cis -C20/C21 stereochemistry (93% yield, 98% ee , >20:1 dr , gram scale). Access to the targeted alkaloids is effected late in the synthesis by implementation of a number of diversity-oriented transformations and late-stage modifications.