A 2.5M solution of BuLi in hexane (1.12 mmol) was added dropwise to a solution of diisopropylamine (387 μl) in a 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone (DMPU)/THF (10 ml/10 ml) mixture at -20° C. The mixture was stirred for 30 min at -20° C., and triethyl 3-methyl-4-phosphonocrotonate (0.68 ml) was then added. The mixture was stirred for 1 h at -20° C. and was added to a solution of (Z)-3-{3-[5-(tert-butyldimethylsilyloxy)pentyloxy]-5,5,8,8-tetramethyl-5,6,7,8-tetrahydro-2-naphthyl}-2-butenal (1.1 g, 2.3 mmol) in THF (5 ml). The reaction medium was permitted to warm to room temperature and was then treated with ethyl acetate/water. After settling, the organic phase was separated and washed twice with water, dried over anhydrous magnesium sulfate and concentrated in a rotary evaporator under vacuum at 40° C. The desired compound was purified by flash chromatography on a silica column.
