A suspension of zinc (1.25 g, 19.1 mmol), 8-methyl-7-propionylindolizino[1,2-b]quinoline-9-(11H)-one (500 mg, 1.43 mmol, as obtained by Kingsburry, W. D., Tetrahedron Lett. 29:6847 (1988)) and silver acetate (250 mg, 1.50 mmol) in anhydrous tetrahydrofuran (10 ml) is agitated at ambient temperature under an argon atmosphere. After 10 minutes, the reaction mixture is activated by the dropwise addition of a molar solution of chlorodiethylaluminium (10 ml, 10 mmol), then ethyl bromoacetate (1.25 ml, 11.3 mmol) is added dropwise and the resultant mixture is left to react for another 5 hours. The reaction is stopped by the successive addition of ethyl alcohol (10 ml) and a saturated solution of potassium and sodium tartrate (10 ml). The resultant mixture is agitated for another hour, filtered and concentrated under reduced pressure. The residue is taken up in dichloromethane (30 ml), washed with water, dried, concentrated and purified by column chromatography (SiO2, CH2Cl2/MeOH:98/2), which produces 93 mg (15%) of desired product in the form of a pale yellow solid, m.p. 185-188° C.
