A solution of 1-(2,4-di-n-propyloxyphenyl)-2-(4-pyridyl)ethane-1,2-dione from Step D (61 mg, 0.19 mmol), ammonium acetate (144 mg, 1.87 mmol) and 4-chlorobenzaldehyde (33 mg, 0.23 mmol) in acetic acid (1.5 mL) was heated to 100° C. for 3.5 h. After cooling to 0° C., the ice (4g), ethyl acetate (2 mL) and a concentrated solution of ammonium hydroxide was added until the pH was 10. The layers were separated and the aqueous layer extracted with ethyl acetate. The combined organic extracts were successively washed with water and saturated salt solution and dried over anhydrous sodium sulfate. The mixture was filtered and the solvent removed by rotoevaporation. The residue was purified by flash column chromatography on silica gel eluted with 0-3% methanol in methylene chloride to yield the title compound as a cream-colored solid (25 mg, 30% yield), mass spectrum (CI) m/e=448 (M+1)+.
