Catalytic Asymmetric Synthesis of Highly Substituted Pyrrolizidines.

A catalytic asymmetric double (1,3)-dipolar cycloaddition reaction has been developed. Using a chiral silver catalyst, enantioenriched pyrrolizidines can be prepared in one flask from inexpensive, commercially available starting materials. The pyrrolizidine products contain a variety of substitution patterns and as many as six stereogenic centers.

Total synthesis of (+)-lyconadin A and related compounds via oxidative C-N bond formation.

The formation of carbon-nitrogen (C-N) bonds is a fundamental bond construction in organic synthesis and is indispensable for the synthesis of alkaloid natural products. In the context of the synthesis of the architecturally complex Lycopodium alkaloid lyconadin A, we have discovered a highly efficient oxidative C-N bond forming reaction that relies on the union of a nitrogen anion and a carbon anion. Empirical evidence amassed during our synthetic studies suggests that the mechanism of the C-N bond forming process encompasses polar as well as radical processes.