1.049 g of 1-[3,3-bis(4-methoxyphenyl)thioacryloyl)piperazine [prepared as described in step (b) above] and 0.29 ml of triethylamine were dissolved in 30 ml of methylene chloride, and 0.157 g of 3,4,5-trimethoxybenzoyl chloride were added, whilst ice-cooling, to the resulting solution. The reaction mixture was then stirred for 1 hour at room temperature, after which it was poured into water and extracted twice with methylene chloride. The combined extracts were washed with 10% w/v aqueous hydrochloric acid, with a saturated aqueous solution of sodium bicarbonate and with water, in that order, after which they were dried over anhydrous sodium sulfate and evaporated under reduced pressure. The residue was purified by column chromatography through 40 g of silica gel and by medium pressure liquid chromatography using a Lobar B column using mixtures of methylene chloride and ethyl acetate ranging from 9:1 to 4:1 by volume as eluent, to give 1.368 g of the title compound as a yellow powder.
