Unified Synthesis of Polycyclic Alkaloids via Complementary Carbonyl Activation.

A complementary dual carbonyl activation strategy for the syn-thesis of polycyclic alkaloids has been developed. Successful appli-cations include the synthesis of tetracyclic alkaloids harmalanine, harmalacinine, pentacyclic indolo-quinolizidine alkaloid nortetoyobyrine, and octacyclic β-carboline alkaloid peganumine A. The latter synthesis features a protecting-group-free assembly and an asymmetric disulfon-imide catalyzed cyclization. Furthermore, formal syntheses of hirsutine, deplancheine, 10-desbromo-arborescidine A, and oxindole alkaloids rhynchophylline and isorhyncho-phylline have been achieved. Finally, a concise synthesis of berberine alkaloid ilicifoline B was completed.