To a solution of (2S,3R)-3-(n-butyl)-2-hydroxysuccinic acid F-4 (300 mg, 1.58 mmol) and powdered molecular sieves (1 g) in trimethyl orthobenzoate (5 mL) and toluene (5 ml) was added 10-Camphorsulfonic acid (20 mg) and the reaction was heated at 110° C. under vacuum (20 torr) for 5 h. The solution was diluted with ethyl acetate, filtered through Celite and washed with brine, dried (Na2SO4) and then purified by silica gel chromatography to afford 1.2 mmol 2-(2-methoxy-2-phenyl-4-oxo-1,3-dioxolan-5-yl)hexanoic acid I-1 (40%).
