To a solution of L-Alanine (200 g, 2.24 mol), sodium formate (76.0 g, 1.12 mmol), and sodium phosphate dibasic (28.7 g, 202 mmol) in 2.25 L of water adjusted to pH 7.5 was added NAD (2.2 g, 3.21 mmol), pyridoxal-5-phosphate (2.2 g, 8.90 mmol), LDH (0.45 g, 0.22 mol), FDH (4.5 g, 0.20 mol), and TA P1 G5 (4.5 g, 0.22 mol). After all the components were completely dissolved, (3S)-3-(benzyloxy)tetrahydro-4H-pyran-4-one (45 g, 0.22 mol) was added and the pH was adjusted to pH 7.25 with 6 N HCl and aged at 30° C. After 15 h, potassium carbonate (700 g, 5.06 mol) was added slowly, followed by ethyl acetate (2.2 L). The mixture was filtered through a bed of Solka Floc and the cake was washed with ethyl acetate (250 mL). The combined filtrates were separated and the aqueous layer was extracted a second time with ethyl acetate (2 L). The combined organic extracts were concentrated in vacuo to provide crude (3R,4S)-3-(benzyloxy)tetrahydro-2H-pyran-4-amine.
