The stereoselective synthesis of the C(31)-C(39) and C(20)-C(27) fragments of phorboxazole A (1) was achieved from commercially available and inexpensive D-mannitol. Crimmins aldol reaction and a decarboxylative Claisen-type reaction are the key steps for the C(31)-C(39) fragment, and L-proline-catalyzed aldol reaction, Sharpless asymmetric epoxidation, and epoxide ring opening reaction with Gilman's reagent are the key steps for the C(20)-C(27) fragment of phorboxazole.