2.50 g (8.11 mmol) of 4-(6-hydroxyhexyloxy)-3-methoxycinnamic acid methyl ester, 1.96 g (8.51 mmol) of 3,5-dinitrobenzoyl chloride and 10 mg (0.08 mmol) of dimethylaminopyridine were dissolved in 25 ml of methylene chloride. 3.3 ml (40.5 mmol) of pyridine were added dropwise, in the course of 20 minutes at 0° C., to the resulting clear solution. After 2 hours at 0° C. the reaction mixture was partitioned between methylene chloride and water; the organic phase was washed with a saturated sodium bicarbonate solution and repeatedly with water. The organic phase was then dried over magnesium sulphate, filtered and concentrated by evaporation. Chromatography of the residue on 150 g of silica gel using toluenelethyl acetate 9:1 yielded 3.6 g of 3,5-dinitrobenzoic acid 6-[2-methoxy-4-(2-methoxycarbonylvinyl)phenoxy]hexyl ester.
