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.
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