Ammonium Chloride → N-Benzyl-(R)-alpha-methylbenzyl-3(S)-(6-methoxypyridin-3-yl)-beta-alanine ethyl ester

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To a solution of N-benzyl-(R)-α-methylbenzylamine (97.5 g, 462 mmol) in THF (750 mL) at 0° C. was added n-butyllithium (2.5M in hexanes; 178.5 mL, 446 mmol). The dark violet solution was stirred at 0° C. for 20 minutes, cooled to -78° C., and the ester 16-3 (63.7 g, 308 mmol) in THF (250 mL) was added over 60 minutes. The resulting solution was stirred at -78° C. for 1 hr, then cannulated into saturated NH4Cl and extracted with EtOAc, washed with water then brine, dried and concentrated in vacuo to give an oil. Column chromatography (silica gel; hexane/EtOAc 9:1 then 4:1) gave 16-4 as an oil contaminated with N-benzyl-(R)-α-methylbenzylamine. This oil was taken up in 5% AcOH in water and extracted with diethyl ether (4×). The organic layers were dried over MgSO4 and the solvent removed to give the title compound 16-4.

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