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ChEBI: 2-amino-3-hydroxybutanoic acid is an alpha-amino acid that is butanoic acid substituted by an amino group at position 2 and a hydroxy group at position 3. It has a role as a plant metabolite.

In a 1 L autoclave, 144 g (1 mol) of 5-(1-hydroxyethyl)glycolonylurea (CAS:64420-00-4), 68 g of 25% ammonia, 110 g of calcium hydroxide (1.5 mol), 500 g of water and 50 mL of n-butanol were added. The mixture was heated to 160-170°C and the reaction pressure was maintained at 1.5-2.0 MPa for 4 hours. Upon completion of the reaction, the mixture was cooled to room temperature and the pH was adjusted by passing carbon dioxide to 8. The reaction mixture was filtered and the mother liquor was concentrated under reduced pressure. The residue was mixed with 150 g of methanol and refluxed for 2 h. Crystals were precipitated after cooling. 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%.

[1] Patent: CN104892521, 2018, B. Location in patent: Paragraph 0069; 0070