Experimental Procedure

Step 1:

Distilled acetaldehyde (8.00 mL, 128 mmol) is added dropwise to TiCl4 (1.0 M in CH2Cl2, 52.0 mL, 52.0 mmol) at -78 °C. 15 minutes later, ketene silylN,O-acetal (19.6 g, 50.6 mmol) in CH2Cl2 (60 mL) is added dropwise, and then stirred for 45 minutes at -78 °C. The reaction is warmed up to -50 °C and stirred for another 18 hours, and is quenched with saturated aqueous Rochelle’s salt and saturated aqueous sodium bicarbonate. After warming to room temperature, the mixture is washed with ethyl acetate. The organic layer is then washed with brine, dried in magnesium sulfate, and concentrated in vacuo. The product was the purified with column chromatography.

Step 2:

S)-4-Benzyl-3-[(2E,4S,5R)-5-hydroxy-2,4-dimethyl-2-hexenoyl)-2-oxazolidinone (3.54 g, 11.2 mmol) is stirred with imidazole (1.27 g, 18.5 mmol) in DMF (50 mL), while TESCl (2.70 mL,15.6 mmol) was added at room temperature. This was left to stir during the night and later quenched with NH4Cl. It was then extracted with Et2O. The product was then washed with brine and dried with magnesium sulfate, and concentrated in vacuo. The compound was then purified with column chromatography.