Butyl lithium (5.14 ml [12.86 mmol, 1.96 equiv] of a 2.5 M solution in hexanes) is added dropwise to a stirred suspension of ethyl triphenylphosphonium iodide (13.12 mmol, 2.0 equiv) in 60 ml of THF cooled to 0° C. The resulting clear red ylide solution is added dropwise to a rapidly stirred solution of iodine (3.163 g,12.46 mmol, 1.90 equiv) in 90 ml of THF cooled to −78° C. The resulting yellow suspension is stirred vigorously for 10 min at −78° C. and for 30 min at −30 to −40° C. 11.81 ml (11.81 mmol, 1.80 equiv) of a solution of sodium hexamethyidisilazide (NaHMDS, 1.0 M in THF) is added dropwise within 10 min at −30° C. The mixture is stirred for 15 min at −30° C. A solution of (S,4E)-3-(tert-butyidimethylsilyloxy)-4-methyl-5-(2-methylthiazol-4-yl)-pent-4-en-1-al 17 (2.137 g, 6.56 mmol) in 30 ml of THF is added dropwise within 10 min. The mixture is stirred for 10 min at −30° C. and quenched with saturated aqueous ammonium chloride solution (10 ml). Pentane (150 ml) is added and the mixture is filtered to a small plug of silica. The column is eluted with 400 ml of pentane/diethyl ether (4:1). The filtrate is concentrated in vacuo. Purification of the residue by flash column chromatography (pentane/diethyl ether 10:1) affords (S,2Z,6E)-5-(tert-butyidimethylsilyloxy)-2-iodo-6-methyl-7-(2-methylthiazol-4-yl)-hepta-2,6-diene 18 (1.640 g, 54%) as a pale yellow oil. 13C-NMR (100 MHz, CDCl3): δ=164.17; 152.85; 141.50; 131.89; 118.66; 115.01; 102.09; 76.45; 43.47; 33.42; 25.58; 18.98; 17.97; 13.87; −4.90, −5.23 (—SiMe2tBu)
