To a solution of N-Boc-L-allothreonine (0.325 g, 1.48 mmol, 1.00 eq.) and 1-hydroxybenzotriazole hydrate (0.221 g, 1.64 mmol, 1.11 eq.) in dimethylformamide (5 mL) at 0° C. was added 1-(3-dimethylaminopropyl)-2-ethylcarbodiimide hydrochloride (WSC) (0.312 g, 1.63 mmol, 1.10 eq.). After 0.5 hr, a solution of (R) α-methylbenzylamine (0.20 mL, 1.55 mmol, 1.05 eq.) in dimethylformamide (3 mL) was added, followed by 4-methylmorpholine (0.16 mL, 1.46 mmol, 0.98 eq.). After 17 hr, the reaction mixture was poured into a brine/water solution (1:1) and extracted twice with ethyl acetate. The organic layers were combined and washed with aqueous 0.25M potassium hydrogen sulfate, water, aqueous saturated sodium bicarbonate, water, dried over sodium sulfate, and the organic layer concentrated in vacuo to give title compound (0.448 g, 93.9%):
