Synthesis of fulgidic acid and the two possible stereoisomers of chaenomic acid D.

We synthesized fulgidic acid and the proposed structure for chaenomic acid D. The core part of the two natural products was constructed stereoselectively by the addition of acetic acid to the α,ß-unsaturated epoxy alcohol in the presence of a palladium catalyst. Subsequently, the two natural products were synthesized from the intermediate in a few steps. The data for the synthesized fulgidic acid were in good agreement with the reported data. Chaenomic acid was in good agreement with the natural product in the 1H and 13C NMR data, but not in the optical rotation. The 15R-isomer of chaenomic acid was also synthesized, but the 1H and 13C NMR data did not agree with the natural product.