Synthesis
5-Benzyloxy-4-oxo-4H-pyran-2-carboxylic acid was synthesized in the following steps: first, 90 g of tricarboxylic acid was added to a 2000 ml round-bottomed flask, and 660 ml of methanol was added to dissolve the tricarboxylic acid. Subsequently, 88 g of benzyl chloride and 63 ml of 40% sodium hydroxide solution were added, and the reaction was heated and refluxed for 17 h to obtain reaction solution a. After the reaction was completed, reaction solution a was distilled under reduced pressure until the solvent was completely evaporated to obtain a dry residue. After the residue was cooled to room temperature, 60 ml of methanol and 240 ml of water were added, stirred and mixed, then washed and filtered, and 116 g of light yellow solid intermediate was obtained after drying. 116 g of the intermediate was added to a reactor with 2000 ml of water and the reaction system was cooled to -5°C. Under temperature control not exceeding 5°C, sodium periodate was added, followed by dropwise addition of 40 ml of water. After the dropwise addition, the reaction was stirred for 10 minutes, then the reaction temperature was raised to 17°C and stirring was continued for 3 hours. After completion of the reaction, the reaction solution was filtered and the filtrate was adjusted to pH 5-6 with hydrochloric acid. 500 g of ethyl acetate was used to extract the filtrate and separate the organic and aqueous phases. The organic phase was dried and filtered, and the solid obtained was dried to give a final 80 g of white solid, which was the target product 5-benzyloxy-4-oxo-4H-pyran-2-carboxylic acid.
References
[1] Indian Journal of Chemistry - Section B Organic Chemistry Including Medicinal Chemistry, 1991, vol. 30, # 3, p. 358 - 359
[2] European Journal of Medicinal Chemistry, 1994, vol. 29, # 11, p. 893 - 897
[3] Farmaco, 2001, vol. 56, # 4, p. 251 - 256
[4] Chemistry - A European Journal, 2010, vol. 16, # 21, p. 6374 - 6381
[5] ACS Medicinal Chemistry Letters, 2015, vol. 6, # 3, p. 318 - 323
