Trifluoroacetic acid (1 ml) was added to a solution of 2-dimethylamino-4,4-diphenyl-9-decene-5-one (270 mg) in methanol (5 ml) to adjust the pH to 2.0. The solution was rotary evaporated, and the residue was taken up in methanol. A gentle stream of ozone was passed through the solution at -78° C., until the color turned to sky blue. The reaction was warmed to -20° C., and dimethyl sulfide (3 ml) was added. Rotary evaporation of the solution gave a crude material which was flash-chromatographed over silica gel. Elution with chloroform/methanol (30:1) yielded 80 mg of 2-dimethylamino-4,4-diphenyl-5-oxo-nonanal.
