A solution of 9-borobicyclononane (0.5M in THF, 12.6 mL) was added to methyl 6-(benzenesulfonylmethyl)-2-hydroxy-3-(2-vinylfuran-3-yl)-benzoate (Intermediate 24, 1.0 g) in THF (20 mL) at 50° C. and the resultant mixture was stirred and heated at 50° C. for 75 minutes. After cooling to room temperature, 35% hydrogen peroxide (2 mL) was added and the mixture was stirred for 1.5 hours. Water and ethyl acetate were added to the mixture and the organic layer was separated, washed with water, sodium metabisulfite and brine, dried (Na2SO4) and filtered. The filtrate was evaporated to dryness and the residue was purified by chromatography on silica, eluting with a mixture of ethyl acetate and cyclohexane with a gradient of 30-70%. The product was triturated with diethyl ether and the solid was collected by filtration and dried in vacuo to give methyl 6-(benzenesulfonylmethyl)-2-hydroxy-3-[2-(2-hydroxyethyl)-furan-3-yl]-benzoate (0.4 g).
