A stereoselective total synthesis of natural levorotatory polycavemoside A (1) has been achieved. initial investigations produced the properly activated disaccharide unit 18b via the conjoining of building blocks originating from L-fucose and D-xylose. This objective was followed by preparation of the phenylsulfonyl-substituted tetrahydropyran 23 and aldehyde 30. After proper linking of these key compounds, important information had to be garnered on the sequence of steps that would ultimately result in successful access to 1. Although oxidation to generate alpha-diketone 35 and unmasking of the C-13 hydroxyl did give rise efficiently to lactol 36, this functionality did not pave the way for ensuring macrolactonization. When this sequence of steps was reversed, it was indeed possible to arrive at the heavily functionalized precursor 43. However, numerous experiments failed to result in the requisite activation of C-16 for attachment of the trienyl side chain. However, if the E-vinyl iodide was elaborated in advance of alpha-diketone generation, glycosidation, and complete side chain construction, arrival at 1 proceeded without unsurmountable complications to furnish the targeted marine toxin.