[NH2:1][C@@H:2]([C:5]([OH:7])=[O:6])[CH2:3][OH:4].C(=O)([O-])[O-].[K+].[K+].[CH2:14](Br)[C:15]1[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=1.O>C(#N)C>[CH2:14]([N:1]([CH2:14][C:15]1[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=1)[C@H:2]([CH2:3][OH:4])[C:5]([O:7][CH2:14][C:15]1[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=1)=[O:6])[C:15]1[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=1D-serine (10.5 g, 0.1 mol) was stirred with potassium carbonate (69 g, 0.5 mol), benzyl bromide (64.8 g, 0.375 mol) and water (10 mL) in acetonitrile (250 mL) at 55° C. for 24 hours. The reaction mixture was filtered and washed with ethyl acetate. The filtrate was concentrated with silica gel. The product was purified by column chromatography, eluting with 5-20% ethyl acetate in hexanes to give benzyl (2R)-2-(dibenzylamino)-3-hydroxypropanoate (33.36 g, 88%) as a pale-yellow sticky oil. 1H NMR (300 MHz, CDCl3): (ppm) 7.20-7.44 (m, 15H), 5.27 (q, 2H), 3.91 (d, 2H), 3.80 (m, 2H), 3.67 (d, 2H), 3.63 (m, 1H) and 2.52 (dd, 1H).
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