All-in-one: A new and general one-pot reaction sequence initiated by singlet oxygen that transforms simple furan substrates into complex nitrogen-bearing aromatic polycycles having all the structural features of a number of important natural products (for example, the erythrina alkaloids; see scheme, RB = rose Bengal) is reported. The reaction sequence itself uses mild conditions and has wide functional group tolerance.

Total syntheses of (-)-stemospironine and three new diastereoisomeric analogs have been completed through a flexible strategy devised for Stemona alkaloids. The azabicycle 7 is the pivotal intermediate, from which the sequence splits according to each particular target. The most remarkable differential feature for stemospironine is the installation of the spiranic γ-lactone through an intramolecular Horner-Wadsworth-Emmons olefination. The configuration of the stereogenic center at C-11 was controlled by fine-tuning of the synthetic sequence.

A general one-pot reaction sequence is developed to convert simple furan derivatives into nitrogen-bearing polycyclic heterocycles. Key feature of the process is the generation of an N-acyliminium ion in a novel way and subsequent intramolecular trapping with an amine. -(KALAITZAKIS, D.; MONTAGNON, T.; ANTONATOU, E.; BARDAJI, N.; VASSILIKOGIANNAKIS*, G.; Chem. -Eur.