Tetrahydrofurans are important structures found in many natural products. Amphidinolide C, which was isolated from Amphidinium sp., displayed potent cytotoxicity against L1210 and KB cells in vitro (IC₅₀ 5.8 and 4.6 ng/mL, 8.1 and 6.2 nM, respectively), making it one of the most potent members of the amphidinolide family. We recently demonstrated that the palladium catalyzed intramolecular addition of hydroxyl to phosphono allylic carbonates is stereospecific. The stereochemistry of the phosphono allylic carbonate dictates the stereochemistry of the new furan ring for a fixed alcohol stereochemistry. Thus, cross metathesis and cyclization with either the R or S alcohol will yield the cis or trans furan from a common phosphonate intermediate. The vinyl phosphonate products can be transformed into several useful functional groups, e.g. Wacker oxidation to yield the β-ketophosphonate. The application of this chemistry to the synthesis of amphidinolide C will be presented.