Synthesis of the azaspiracid-1 trioxadispiroketal.

The de novo analysis, design, and synthesis of the azaspiracid-1 trioxadispiroketal system is described. A revised structural model was developed on the basis of an independent analysis of the NMR spectral data of the natural product that fit all of the data and the thermodynamically favored spiroketal paradigm. This model was then tested via synthesis using a novel trioxadispiroketalization process and supported by spectroscopic correlation.