Synthesis of Bis(indole) Alkaloids from Arundo donax: The Ynindole Diels–Alder Reaction,Conformational Chirality,and Absolute Stereochemistry

Bis(indole) alkaloids from Arundo donax were synthesized using the first ynindole Diels–Alder reaction. The alkaloids are chiral, having stable enantiomeric conformations with half‐lives of racemization of t_1/2=4150–25100 seconds at room temperature. Their absolute stereochemistry was determined using the exciton chirality method.     

Enantioselective Organocatalytic Intramolecular Aza‐Diels–Alder Reaction

A highly efficient catalytic enantioselective intramolecular Povarov reaction was developed with primary anilines as 2‐azadiene precursors. A wide variety of angularly fused azacycles were obtained without column chromatography in high to excellent yields and with excellent diastereo‐ and enantioselectivity (d.r.>99:1 and up to e.r. 99:1). Furthermore, the catalyst loading could be lowered to 1 mol %, and the obtained azacycles could be used as key intermediates for further transformations to generate additional molecular diversity.     

Development of a Divergent Synthetic Route to the Erythrina Alkaloids: Asymmetric Syntheses of 8‐Oxo‐erythrinine,Crystamidine, 8‐Oxo‐erythraline,and Erythraline

A general synthetic methodology toward the erythrina alkaloids has been developed. Inspired by a proposed biosynthetic mechanism, the medium‐sized chiral biaryl lactam was asymmetrically transformed into the common core A–D rings by a stereospecific singlet oxygen oxidation of the phenol moiety, followed by a transannular aza‐Michael reaction to the dienone functionality. The late‐stage manipulation of the oxidation and oxygenation states of the functional groups on the peripheral moieties enabled the flexible syntheses of the erythrina alkaloids.