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To a solution of glycolaldehyde dimethyl acetal (25 g, 236 mmol) in 750 mL of THF at 0° C. was added portionwise 14.1 g (353 mmol) of a 60% suspension of NaH in oil. The solution was warmed to room temperature, and then to 60° C. overnight. After cooling to room temperature, and then to 0° C., 69.9 g (353 mmol) of bromoacetaldehyde diethyl acetal in 200 mL of THF was added dropwise over 30 minutes. The reaction was warmed to room temperature, and then to reflux for 2 days. The reaction was cooled to room temperature, filtered through a pad of celite, and concentrated by rotary evaporation while keeping the bath temperature below 40° C. The residue was purified by column chromatography on silica gel (0 to 30% EtOAc in hexanes) to provide C-1 as a yellow oil. Data for C-1:1 H NMR (CDCl3, 500 MHz) δ 4.65 (m, 1H), 4.5 (m, 1H), 3.7 (m, 2H), 3.55 (m, 6H), 3.4 (s, 6H), 1.2 (M, 6H) ppm.

1. customto 60° C.
2. customovernight
3. temperatureAfter cooling to room temperature
4. temperatureThe reaction was warmed to room temperature
5. temperatureto reflux for 2 days
6. temperatureThe reaction was cooled to room temperature
7. filtrationfiltered through a pad of celite
8. concentrationconcentrated by rotary evaporation
9. customthe bath temperature below 40° C
10. customThe residue was purified by column chromatography on silica gel (0 to 30% EtOAc in hexanes)
11. customto provide C-1 as a yellow oil