Synthetic studies on shellfish toxin azaspiracid-1

Azaspiracids (AZAs) are a group of shellfish toxin responsible for the poisoning called "azaspiracid poisoning (AZP)" prevailed in a coastal region of north Europe to northwest Africa since 1995. To establish the molecular basis including its chemical structure and its mode of biological action, several synthetic studies have been developed on azaspiracid-1 (AZA-1). In this review, studies on the syntheses of the FGHI- and EFGHI-ring domains corresponding to a lower half of AZA-1, reported by groups of Forsyth, Evans, Nicolaou, and us, are summarized. Retrosynthetic analysis, fragment synthesis and their assembly, and stereoselective construction of the unique spiroaminal HI-ring domain are main topics of this review. Furthermore, total syntheses successfully made by Evans and Nicolaou groups are described.