Acetic Acid → (3R,4S,7S) 3,7-dibenzyloxy-4-vinyldodeca-5-enecarboaldehyde

While stirring, 776 mg (1.67 mM) of (3R,4S,7S) 3,7-dibenzyloxy-4-vinyl-1,1-dimethoxydodeca-5-ene [8] described above was heated in a mixture of 13 ml of 80% acetic acid and 2 ml of tetrahydrofuran at 40° C. for 5 hours. Completion of the reaction was confirmed by thin layer chromatography. Then, the reaction solution was poured into saturated sodium bicarbonate aqueous solution. The mixture was extracted 3 times with a solvent mixture of diethyl ether:hexane=7:3. The extracts were combined and washed sequentially with saturated sodium bicarbonate aqueous solution and saturated sodium chloride aqueous solution. After drying over anhydrous magnesium sulfate, the solvent was distilled off under reduced pressure to give 701 mg (1.67 mM) of (3R,4S,7S) 3,7-dibenzyloxy-4-vinyldodeca-5-enecarboaldehyde [9]. Yield, 100%.