Abstract
Polycavernoside A (1) has been isolated as one of the sources of human intoxication from the red alga Polycavernosa tsudai by Yasumoto et al. in 1993. They have proposed the planar structure of 1, which is a novel macrolide disaccharide, on the basis of ^1H and ^<13>C NMR spectra. However, although the respective relative configurations of the tetrahydrofuran ring, the tetrahydropyran ring, and the sugar moieties have been clarified, the absolute configuration of the whole molecule has not been established yet. We have started the total synthesis of this compound, because of its unusual molecular structure, the significant toxic activity, and the lack of a satisfactory natural source. We describe herein the construction of the southern part (9), macrolactone part (25), and triene model compound (34) as well as the determination of the relative configration of 1.
