24830-94-2

64420-00-4

72-19-5

The general procedure for the synthesis of L-threonine from 5-(1-hydroxyethyl)urea (CAS:64420-00-4) is as follows: in a 1 L autoclave, 144 g (1 mol) of 5-(1-hydroxyethyl)urea, 68 g of 25% ammonia solution, 110 g of calcium hydroxide (1.5 mol), 500 g of deionized water and 50 mL of n-butanol were added in sequence. The reaction mixture was heated to 160-170°C and the reaction pressure was maintained at 1.5-2.0 MPa for 4 hours. After completion of the reaction, the reaction was cooled to room temperature, and carbon dioxide gas was introduced to adjust the pH of the reaction solution to 8. The insoluble material was removed by filtration, and the mother liquor was concentrated under reduced pressure. To the concentrated residue, 150 g of methanol was added and refluxed for 2 hours, then cooled to room temperature and crystals were precipitated. The crystals were collected by filtration, and the filter cake was dried under vacuum at 120°C for 4 h. 106.4 g of 2-amino-3-hydroxybutyric acid (L-threonine) was obtained with a purity of 96% and a yield of 89.4%.