Palladium(0)-mediated desymmetrization of meso tetraols: an approach to the C3-C17 bis-oxane segment of phorboxazoles A and B.

[reaction: see text] meso-Tetraol bis(allylic acetates) 2 and 5 were synthesized via two-directional chain elongation. A palladium-mediated, ligand-controlled desymmetrization provided the desired bis-oxanes in greater than 98% ee. Bis-oxanes 1 and 4 represent potential synthetic intermediates for the C3-C17 subunits of phorboxazoles A and B.