Enantiocontrolled Synthesis of (+)-Boronolide

(+)-Boronolide 1, a δ-lactonic polyacetoxy natural product isolated from the bark and branches of Tetradenia fruticosa and from the leaves of Tetradenia barberae, has been stereoselectively synthesized, the key steps being the chemoselective Sharpless asymmetric dihydroxylation of (E)-1-(tert-butyldimethylsiloxy)-7-dodecen-5-yne (6), Lindlar reduction of the triple bond of diacetate 9, and further diastereoselective dihydroxylation of the resulting cis-olefin 5.