11.6 g (77 mmol) of t-butyldimethylsilane, 7.8 g (77 mmol) of triethylamine and 0.76 g (6.2 mmol) of 4-dimethylaminopyridine were added, in turn, and with ice-cooling, to a solution of 14.5 g (62 mmol) of 2-t-butyl-5-[(1E)-3-hydroxy-1-propenyl]-1-nitrobenzene [prepared as described in step (iii) above] in 140 ml of dimethylformamide, and the resulting mixture was stirred for 1 hour. At the end of this time, the reaction mixture was poured into ice-water and then extracted with diethyl ether. The extract was washed with a 10% w/w aqueous solution of hydrochloric acid, with a saturated aqueous solution of sodium hydrogencarbonate and with a saturated aqueous solution of sodium chloride, in that order, after which it was dried. The solvent was then removed by distillation under reduced pressure, and the resulting residue was purified by column chromatography through silica gel, using a 1:15 by volume mixture of ethyl acetate and hexane, to give 21 g of the title compound as crystals, melting at 33°-34° C. (from ethyl acetate-hexane).
