Enantioselective Formal Synthesis of (−)-Neoxaline Enabled by an Asymmetric Ir-Catalyzed Reverse Prenylation

We report the enantioselective formal synthesis of neoxaline, an archetypal member of the oxaline alkaloids. An initial approach employs an asymmetric deaminative cross-coupling to install the 1,1-dimethylallyl (“reverse prenyl”) moiety onto an oxindole framework. Subsequent strategies employ iridium-catalyzed reverse prenylation onto tryptamine scaffolds, enabling the facile construction of a densely functionalized α-carboline framework. The route detailed herein represents a potentially general strategy for the synthesis of related oxaline alkaloids.