2-Hydroxy-3(6'-trimethylsilylhexyl)-1,4-naphthoquinone (337 mg, 1.02 mmol), prepared from 2-benzoyloxy-1,4-naphthoquinone and trimethylsilylheptanoic acid by the method of Example 1 followed by the method of Example 2, was dissolved in dioxane (2.5 ml) under nitrogen. Sodium carbonate (120 mg) in water (2.5 ml) was added followed by an excess of 30% (w/v) hydrogen peroxide (200 μl). The mixture was heated at 70° C. for 40 minutes during which time the reaction mixture turned from red to colourless. The reaction mixture was allowed to cool and 20% (w/v) copper sulphate solution (100 μl) was added and the solution stirred until bubbling ceased. 25% (w/v) sodium hydroxide solution (2 ml) and 20% (w/v) copper sulphate solution (5 ml) were then added and the reaction mixture heated at 70° C. for 30 minutes. The mixture was allowed to cool and acidified to pH 2 with 1N hydrochloric acid. The product was extracted into diethyl ether and the ether extract was then washed with brine, dried over anhydrous magnesium sulphate and concentrated in vacuo. The crude material was chromatographed using 5% diethyl ether/hexane as eluent to give 2-hydroxy-3(5'-trimethylsilylpentyl)-1,4-naphthoquinone (202 mg) which was recrystallised from hexane, m. pt. 73-75° C. NMR peaks at: 184.6, 181.4, 153.0, 134.8, 132.9, 132.7, 129.4, 126.7, 126.0, 124.8; 33.6, 27.9, 33.7, 23.2, 16.5; -1.7.
