A mixture of tert-butyl (1S,2R)-3-amino-1-(3,5-difluorobenzyl)-2-hydroxypropylcarbamate (170 mg, 0.538 mmol), 1H-pyrrole-2-carbaldehyde (51 mg, 0.538 mmol), and triethylamine (60 mg, 0.592 mmol) was stirred in chloroform (10 mL) containing magnesium sulfate for 4 h. The reaction mixture was filtered and concentrated under reduced pressure. The resulting residue was dissolved in 2-propanol (10 mL) and sodium borohydride (26 mg, 0.699 mmol) was added. The reaction mixture was stirred overnight and then treated with methanol. The reaction mixture was concentrated under reduced pressure. Purification by flash column chromatography (silica, 9:1 chloroform/methanol) gave tert-butyl (1S,2R)-1-(3,5-difluorobenzyl)-2-hydroxy-3-[(1H-pyrrol-2-ylmethyl)amino]propylcarbamate (132 mg): 1H NMR (300 MHz, CD3OD) δ 6.82 (m, 4H), 6.21 (s, 1H), 6.09 (m, 1H), 4.09 (s, 2H), 3.66 (m, 2H), 3.19 (m, 1H), 3.13 (m, 1H), 3.03 (m, 1H), 2.88 (m, 1H), 1.31 (s, 9H).
