1H-NMR (CDCl3) δ: 3.96 (3H, s), 5.13 (2H, s), 6.63 (1H, d, J=8.4 Hz), 6.70 (1H, d, J=9.8 Hz), 6.71 (1H, d, J=8.4 Hz), 7.45 (1H, t, J=8.4 Hz), 8.24 (1H, d, J=9.8 Hz), 9.66 (1H, s) (2) To 2.4 mL of dichloromethane solution containing 0.10 g of (5-methoxy-2-oxoquinolin-1(2H)-yl)acetaldehyde, 0.16 g of tert-butyl(2,3-dihydro-1,4-benzodioxin-6-ylmethyl)(piperidin-4-yl)carbamate and 24 μL of acetic acid were added, and stirred for 20 min. To the reaction mixture, 0.15 g of sodium triacetoxyborohydride was added, and stirred for 50 min. Chloroform and aqueous saturated sodium hydrogen carbonate solution were added, the organic layer was separated, and the aqueous layer was extracted with chloroform. The organic layer and extracts were combined, washed with aqueous saturated sodium chloride solution, dried over anhydrous magnesium sulfate, and the solvent was removed under reduced pressure. The residue thus obtained was purified by silica gel column chromatography [eluent; hexane:ethyl acetate=1:3], to give 0.18 g of tert-butyl(2,3-dihydro-1,4-benzodioxin-6-ylmethyl)(1-(2-(5-methoxy-2-oxoquinolin-1(2H)-yl)ethyl)piperidin-4-yl)carbamate as a pale yellow oil.
