Pyrrolizidine Alkaloids.

Naturally occurring pyrrolizidine alkaloids (PAs) are isolated from plants and other sources. The interest of the scientific community in these compounds owes itself to their high toxicity and biological activity, as well as to the challenge of synthesizing their pyrrolizidine scaffold. This review encompasses a wide range of topics found in the literature from 1995 to date, including the occurrence, biosynthesis, toxicity (hepatotoxicity, genotoxicity, and tumorigenicity), biological activity, and pharmacological properties (glycosidase inhibitory activity) of these secondary metabolites. Particular attention is given to the chemistry of PAs, addressing general strategies for formal and total syntheses via amino-based substrates, pyrroles, and pyrrolidine-based derivatives.