A concise approach to the core structures of pinnaic acid and halichlorine?

Organic & Biomolecular Chemistry Pub Date: 2009-06-15 DOI: 10.1039/B903904J

Abstract

An efficient and flexible synthetic approach to the core structures of pinnaic acid and halichlorine is described using spirocyclic nitrone 4 as a key intermediate. 1,3-Dipolar cycloaddition of 4 with dipolarophile 8 provides access to the azaspirocyclic core of pinnaic acid 5 while the spiroquinolizidine core of halichlorine 6 has been synthesised viacycloaddition of 4 with dipolarophile 29. Nitrone 4 is accessed by oxidative ring opening of isoxazolidine 9. The utility of this synthetic strategy in the synthesis of C5 substituted analogues of pinnaic acid is also demonstrated.

Graphical abstract: A concise approach to the core structures of pinnaic acid and halichlorine
Recommended Literature