(2S)-3-Methyl-2-[(3-nitroquinolin-4-yl)amino]butan-1-ol (3.97 g, 14.4 mmol) was dissolved in 15 mL of dry pyridine and treated with tert-butyldimethylsilyl chloride (2.40 g, 15.9 mmol) and a catalytic amount of 4-(dimethylamino)pyridine (DMAP) (176 mg, 1.44 mmol). The reaction mixture was stirred under N2 and heated to 56° C. After 2 days, the reaction mixture was concentrated under reduced pressure. The resulting solid was partitioned between 100 mL of H2O and 100 mL of ethyl acetate. The layers were separated and the organic portion was washed with H2O and brine. The organic portion was then dried over Na2SO4, filtered and concentrated under reduced pressure. Chromatography (SiO2, 20% ethyl acetate/hexanes) gave N-[(1S)-1-({[tert-butyl(dimethyl)silyl]oxy}methyl)-2-methylpropyl]-3-nitroquinolin-4-amine (5.46 g) as a yellow syrup.
