Cl.[CH3:2][O:3][C:4](=[O:8])[C@H:5]([CH3:7])[NH2:6].[CH3:9][O:10][CH:11]([O:14][CH3:15])[CH:12]=O.S([O-])([O-])(=O)=O.[Mg+2].C([BH3-])#N.[Na+]>CO>[CH3:2][O:3][C:4](=[O:8])[C@@H:5]([NH:6][CH2:12][CH:11]([O:14][CH3:15])[O:10][CH3:9])[CH3:7]To a solution of L-alanine methyl ester hydrochloride (5.00 g, 35.8 mmol) in MeOH (100 mL) were added at 0° C. dimethoxyacetaldehyde (45% solution in tert-butyl methyl ether, 12.0 mL, 47 mmol) magnesium sulfate (38.8 g, 322 mmol), and sodium cyanoborohydride (3.08 g, 46.6 mmol). The ice bath was removed, then after 16 h the excess reagent was destroyed by careful addition of sat. aq. sodium hydrogencarbonate solution at 0° C. The reaction mixture was partitioned between sat. aq. sodium hydrogencarbonate solution and EtOAc. The organic layer was washed with brine, dried over magnesium sulfate, filtered, and evaporated to afford the title compound (5.50 g, 80%). Light yellow liquid, MS (ISP)=192.2 (M+H)+.
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