[NH2:1][CH:2]([C:7]1[CH:8]=[N:9][CH:10]=[CH:11][CH:12]=1)[CH2:3][C:4]([OH:6])=[O:5].S(=O)(=O)(O)O.[CH2:18](O)[CH3:19]>>[NH2:1][CH:2]([C:7]1[CH:8]=[N:9][CH:10]=[CH:11][CH:12]=1)[CH2:3][C:4]([O:6][CH2:18][CH3:19])=[O:5]To a stirred suspension of 114 g (0.69 mole) of β-amino-β-(3-pyridyl)propionic acid in 2,850 ml of ethanol was added a 5° C. solution of 417 g of sulfuric acid in 240 ml of ethanol. After stirring for 1 hour, the resultant clear solution was left standing at room temperature for 48 hours and then concentrated to incipient crystallization in vacuum at a temperature below 50° C. The solution was added to a suspension of 715 g of sodium bicarbonate in 1430 ml of water over 1 hour. The temperature of the solution was maintained between 0° to 5° C. After stirring an additional 30 minutes, 300 ml of carbon tetrachloride was added and the admixture stirred for 10 minutes. The by-product salt was removed by filtration and the aqueous layer was extracted thoroughly with carbon tetrachloride. The combined organic extracts were dried and concentrated under vacuum to yield 87.11 g (65% yield) of crude ethyl β-amino-β-(3-pyridyl)propionate as a slightly viscous green liquid.
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