To a solution of cis-4-benzylamino-6,7-dimethyoxy-2-methyl-3,4-dihydro-2H-quinoline-1-carboxylic acid benzyl ester (Example 2B) (150 mg, 0.34 mmol) in anhydrous dichloromethane (5 mL) were added pyridine (0.20 mL, 2.3 mmol) and ethyl chloroformate (0.16 mL, 1.7 mmol). The reaction was stirred at room temperature overnight. The reaction mixture was then poured into water (20 mL), and aqueous 2N KOH (10 mL) was added. The solution was stirred for 30 min, then the mixture was extracted with ether (3×25 mL). The organic phases were combined and washed with 1N HCl (3×10 mL) and then a saturated sodium bicarbonate solution (10 mL). The organic layer was dried over sodium sulfate, filtered and concentrated in vacuo to give 190 mg of crude product. Purification by silica gel chromatography using 0-40% ethyl acetate/hexanes as eluent afforded the desired final product (146 mg, 83%): MS m/z 519 (M+ +1), 537 (M+ +19), 340 (M+ -178); 1H NMR (CDCl3) δ 6.99 (C8, s, 1H), 6.42 (C5, s, 1H).
