20 ml of aqueous hydrofluoric acid (40%) at 0° C. is added to a vigorously stirred solution of (S,4E)-1,3-di-(tert-butyldimethylsilyloxy)-4-methyl-5-(2-methylthiazol-4-yl)-pent-4-ene 15 (13.255 g, 30.0 mmol) in 120 ml of diethyl ether and 120 ml of acetonitrile. Finely ground splinters of glass (133 mg) are added and the mixture is stirred for 2 h at 0° C. and analyzed by tic. If starting material can still be detected another portion of hydrofluoric acid (20 ml) is added and stirring is continued for 1 h. The reaction is quenched by carefully adding solid sodium bicarbonate (84.0 g, 1.0 mol) within 15 min at 0° C. After stirring for 30 min at 0° C. water is aaded until the salts dissolve (the pH is adjusted to 6-8 by further addition of sodium bicarbonate, if necessary). The mixture is extracted with dichloromethane (4×200 ml). The combined organic extracts are washed with brine (100 ml), dried over magnesium sulfate, and concentrated in vacuo. Purification of the residue by flash column chromatography (pentane/diethyl ether 4:1) affords (S,4E)-3-(tert-butyldimethylsilyloxy)-1-hydroxy-4-methyl-5-(2-methylthiazol-4-yl)-pent-4-ene 16 (8.255 g, 84%) as a viscous, colourless oil.
