US 11,753,389 B2
Method for preparing dihydroquercetin
Junqiu Ji, Anhui (CN); Xiaochang Li, Anhui (CN); Bing Li, Anhui (CN); Qiao Li, Anhui (CN); Qing Miao, Anhui (CN); Limei Liu, Anhui (CN); and Jinping Liu, Anhui (CN)
Assigned to HEFEI LIFEON PHARMACEUTICAL CO., LTD., Anhui (CN)
Appl. No. 18/8,044
Filed by HEFEI LIFEON PHARMACEUTICAL CO., LTD., Anhui (CN)
PCT Filed May 7, 2022, PCT No. PCT/CN2022/091499
§ 371(c)(1), (2) Date Dec. 2, 2022,
PCT Pub. No. WO2022/237689, PCT Pub. Date Nov. 17, 2022.
Claims priority of application No. 202110519620.6 (CN), filed on May 10, 2021.
Prior Publication US 2023/0192639 A1, Jun. 22, 2023
Int. Cl. C07D 311/32 (2006.01); C07D 311/40 (2006.01)
CPC C07D 311/32 (2013.01) [C07D 311/40 (2013.01)] 20 Claims
 
1. A preparation method of dihydroquercetin, comprising the steps of:
adjusting the alkalinity of a water reaction solvent with an alkalizing reagent, to obtain an alkaline aqueous solution;
dissolving quercetin dihydrate in the alkaline aqueous solution, and adding an oxygen-containing sulfite binary combined reducing agent to carry out reduction reaction, to obtain an endpoint reduction reaction solution;
diluting the endpoint reduction reaction solution with water, and then acidizing, aging, and filtering a resultant to obtain a filtrate and a filter cake;
subjecting the filtrate to extraction, washing, drying, and vacuum concentration to obtain a concentrated crude product; and
repeatedly crystallizing the concentrated crude product to obtain the dihydroquercetin,
wherein the oxygen-containing sulfite binary combined reducing agent is selected from the group consisting of a binary combination of sodium hydrosulfite and sodium pyrosulfite and a binary combination of sodium hydrosulfite and sodium bisulfite.