4-oxo-2-tetrahydropyranoic acid (10g) was dissolved in 150mL glacial acetic acid, added to the autoclave with 5% Pd/C (2g), passed into the hydrogen, at 0.4MPa pressure, 75 under the reaction until the system no longer absorbs hydrogen until the disappearance of the raw material point detected by TLC. Cooling, filtration, spinning to remove the solvent, to obtain the black material, and then dissolved in ether, with sodium bicarbonate. Extraction (3150mI), ether washing (3150mI), acidification, filtration, to get white solid, toluene recrystallization, to get white crystals of 2-tetrahydropyranoic acid 8.2 g.
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