To a solution of 3.4 mL (48 mmol) dimethyl sulfoxide in 140 mL dry methylene chloride at -78° C. is added dropwise 3.0 mL (35 mmol) oxalyl chloride. The solution is stirred for 15 minutes and a solution of 2.57 g (7.1 mmol) methyl 2,2-dimethyl-4-(2-hydroxyethyl)-8-(t-butyldimethylsiloxy)octanoate in 20 mL dry methylene chloride is added slowly. The solution is stirred at -60° C. for 15 minutes and 15 mL (0.11 mole) triethylamine is added. The reaction is allowed to warm to room temperature and diluted with methylene chloride. The organic layer is washed with saturated aqueous sodium bicarbonate solution, water and brine. The organic phase is dried, filtered and concentrated to dryness. The oil is dissolved in ether and the solution is washed with water. The organic phase is dried, filtered and concentrated to give methyl 2,2-dimethyl-4-formylmethyl-8-(t-butyldimethylsiloxy)-octanoate; NMR (CDCl3) delta 9.8 (t,1H), 3.67 (s,3H), 1.2 (s,6H), 0.89 (s,9H).
