(Method J9A) To the mixture of 4-(dimethylamino)-1-naphthalenecarboxylic acid (1/62) (0.32 g, 1.5 mmol) and N-hydroxysuccinimide (0.21 g, 1.8 mmol) in methylene chloride (10 ml), dicyclohexylcarbodiimide (0.37 g, 1.8 mmol) in methylene chloride (2 ml) was added. A white precipitate appeared. The reaction mixture was after 0.5 h filtered through a pad of Celite® into the solution of methyl 5-aminopentanoate hydrochloride (2b) (0.33 g, 1.9 mmol) in methylene chloride, followed by the addition of triethylamine (2.6 ml, 19 mmol). The reaction mixture was stirred at room temperature overnight, evaporated, suspended in water and extracted with 3 portions of ethyl acetate. The organic layer was washed with brine and dried (Na2SO4). The solvent was removed and the residue (0.55 g) was purified on silica gel with light petrol-ethyl acetate (2:1) as eluent to give the title compound (0.31 g, 63%), Rf 0.48 (light petrol-ethyl acetate 1:1). 1H NMR (200 MHz, DMSO-d6, TMS) δ: 1.51-1.59 (4H, m), 2.38 (2H, t, 6.9 Hz), 2.85 (6H, s), 3.26-3.36 (m, overlapped with a signal from DMSO), 3.61 (3H, s), 7.08 (1H, d, 7.6 Hz), 7.48-7.57 (3H, m), 8.15-8.27 (2H, m), 8.43 (1H, t, br).
