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A solution of glycine (45 g, 0.60 mol) and anisaldehyde (122 g, 0.900 mol) in ethanol (1.5 L) was stirred at ambient temperature and KOH (82.7 g, 1.47 mol) was added. The reaction mixture was stirred overnight at ambient temperature. The mixture was concentrated under vacuum the majority of ethanol. The residue was dissolved in water (800 mL) and the solution was adjusted to pH=5 with 4 N aqueous HCl. The resulting mixture was washed with EtOAc (200 mL×2) to remove any impurities. The aqueous layer was concentrated to a volume of ˜400 mL. The mixture was filtered and the filtration cake was washed thoroughly with water (100 mL×2) and dried to afford 2-amino-3-hydroxy-3-(4-methoxyphenyl)propanoic acid (29 g, 23% yield, threo-) as a colorless solid.

1. concentrationThe mixture was concentrated under vacuum the majority of ethanol
2. dissolutionThe residue was dissolved in water (800 mL)
3. washThe resulting mixture was washed with EtOAc (200 mL×2)
4. customto remove any impurities
5. concentrationThe aqueous layer was concentrated to a volume of ˜400 mL
6. filtrationThe mixture was filtered
7. washthe filtration cake was washed thoroughly with water (100 mL×2)
8. customdried