Formic Acid → Acetic anhydride formic acid

Temperatur

50 °C

Formic acid (0.5 ml, 13.3 mmol) was added to acetic anhydride (1.0 ml, 10.6 mmol) under ice-cooling, the mixture was stirred for one hour at 50° C. to give formic acid-acetic acid anhydride. To a tetrahydrofuran (10 ml) solution of the compound 2 (200 mg, 0.34 mmol) obtained in Example 10 was added the formic acid-acetic acid anhydride (0.3 ml) under ice-cooling and the mixture was stirred for 30 minutes. The mixture was stirred for one hour. The reaction mixture was concentrated under reduced pressure. The residue was purified by silica gel column chromatography to give colorless solid substance (125 mg) of the titled compound.