Ozone was bubbled through a -78° C. methanol (500 mL) solution of diene, 1-(2-propene-1-oxy)-2-(2-propene-1-yl)-3-(tert-butyldiphenylsilyloxy)-propane, (7.41 g, 18.80 mmol). After the disappearance of the starting material (TLC, 25% ethyl acetate/hexane), the reaction mixture was purged with N2 and sodium borohydride (2.13 g, 56.30 mmol) was added. The reaction was warmed to room temperature. After 12 hours, the reaction was concentrated. The white residue was quenched with water, and extracted with ethyl acetate (100 mL×3). The combined organic phase was washed with brine, dried, and concentrated under reduced pressure to give a residue. The residue was eluted through a short silica gel column with ethyl acetate/hexane (10% to 50% ethyl acetate gradient) and evaporation of the eluting solvent gave the 1,7-diol, 1-(2-hydroxyethoxy)-2-(2-hydroxyethyl)-3-(tert-butyldiphenylsilyloxy)-propane (5.48 g, 72% yield).
