Chem. Pharm. Bull. 53(1) 1—10 (2005)

Natural products have played a significant role in the development of organic chemistry, especially in the area of fine organic synthesis. Compounds with unprecedented molecular architecture and multiple functional groups have created opportunities for devising new strategies and methodologies as well as evaluating the practicability of known methods and reactions. In addition, making target molecules in a practical fashion represents one of the major challenges in synthetic organic chemistry. A cascade sequence can lead to an increase in molecular complexity by combining a series of reactions in one synthetic operation. Designing a “one-pot” sequence for the construction of highly complex molecules might provide one good solution to the foregoing problem, i.e., practical synthesis. In this context, we have explored the tandem carbonyl ylide formation/1,3-dipolar cycloaddition methodology for the construction of the common 2,8-dioxabicyclo[3.2.1]octane structure of zaragozic acids, while the viability of the dispiroketalization via a tandem double hemiketal formation/intramolecular hetero-Michael addition process was investigated during the course of our synthetic studies on the shellfish poison pinnatoxin A. As space is limited, this review highlights our total syntheses of zaragozic acid C using two convergent approaches, the comparison of which might confirm the power and vitality of the tandem reaction sequence in the synthesis of natural products.