A solution of (Z)-5,5-bis(3-methoxyphenyl)-2,4-pentadienoic acid (1.85 g) and 4-nitrophenol (0.912 g) in dichloromethane (25 mL) was treated with 1,3-dicyclohexylcarbodiimide (1.23 g). The mixture was stirred at 0°-5° C. for 1 hour, then at room temperature for 1 hour. The usual work up furnished 2.2 g of crude (Z)-5,5-bis(3-methoxyphenyl)-2,4-pentadienoic acid 4-nitrophenyl ester contaminated with the corresponding (E)-isomer, purification of the product by HPLC (dichloromethane-hexane; 3:1) yielded 1.2 g of the (Z)-isomer (Z)-5,5-bis(3-methoxyphenyl)-2,4-pentadienoic acid 4-nitrophenyl ester as an oil.
