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0 °C

A solution of (S)-4-benzyl-2-oxazolidinone (177.4 g, 1 mol) and t-butyl alcohol (74.1 g , 1 mol) in anhydrous tetrahydrofuran (2 L) was cooled to -78° C. A 1.6M solution of n-butyllithium in hexane (1280 mL, 2 mol) was added maintaining a temperature below -30° C. After recooling to -78° C. the (E) 6-(1,3-dihydro-4-hydroxy-6-methoxy-7-methyl-3-oxoisobenzofuran-5-yl)-4-methyl-4-hexenoyl chloride solution (1 mol) was added and the mixture was allowed to warm to 0° C. over 2 hours. 2N Hydrochloric acid (1.5 L) and ethyl acetate (1 L) were added. The organic layer was washed sequentially with saturated aqueous sodium bicarbonate (0.5 L), 2N hydrochloric acid (0.5 L), and brine (1 L). After drying over sodium sulfate, the organic layer was evaporated at reduced pressure to leave the crude imide as a tan solid. Recrystallization from ethyl acetate/hexane (2.5 L/2.5 L) gave (S)-4-benzyl-3-[(E) 6-(1,3-dihydro-4-hydroxy-6-methoxy-7-methyl-3-oxoisobenzofuran-5-yl)-4-methyl-4-hexenoyl]-2-oxazolidinone as off-white, shiny plates, m.p. 112°-113° C.

1. temperaturemaintaining a temperature below -30° C
2. customAfter recooling to -78° C.
3. additionwas added
4. washThe organic layer was washed sequentially with saturated aqueous sodium bicarbonate (0.5 L), 2N hydrochloric acid (0.5 L), and brine (1 L)
5. dry with materialAfter drying over sodium sulfate
6. customthe organic layer was evaporated at reduced pressure
7. customto leave the crude imide as a tan solid
8. customRecrystallization from ethyl acetate/hexane (2.5 L/2.5 L)