A solution of 1,1-dimethylethyl 3-[[[4-(methoxycarbonyl)phenyl]methyl]amino]-8-azabicyclo[3.2.1]octane-8-carboxylate (2.1 g, 5.7 mmol) and formaldehyde (1 mL of 37% solution in water) in dichloroethane (20 mL) was stirred as acetic acid (0.37 g, 6.9 mmol) and sodium triacetoxyborohydride (1.7 g, 8 mmol) were added. The reaction was stirred for 17 hours. The reaction was treated with a saturated aqueous solution of sodium bicarbonate and extracted with ethyl acetate (2×). The combined organic extracts were dried and concentrated. Purification by flash chromatography on silica gel using a gradient of ethyl acetate in hexane gave 1.7 g of 1,1-dimethylethyl 3-[[[4-(methoxycarbonyl)phenyl]methyl]methylamino]-8-azabicyclo[3.2.1]octane-8-carboxylate.
