[OH:1][CH:2]([C:10]1[C:15]([CH3:16])=[CH:14][C:13]([CH3:17])=[C:12]([CH3:18])[C:11]=1[OH:19])[CH2:3][CH2:4][CH2:5][CH2:6][C:7]([OH:9])=[O:8].O.[O]N(S(=O)([O-])=O)S(=O)([O-])=[O:24].[K+].[K+].Cl>[OH-].[Na+]>[CH3:18][C:12]1[C:11](=[O:19])[C:10]([CH:2]([OH:1])[CH2:3][CH2:4][CH2:5][CH2:6][C:7]([OH:9])=[O:8])=[C:15]([CH3:16])[C:14](=[O:24])[C:13]=1[CH3:17]To a solution of 6-hydroxy-6-(2'-hydroxy-3',4',6'-trimethylphenyl)hexanoic acid (formula III-3 wherein R=H3C, X=H, Y=OH, n=4, in the free form) (0.158 part) in 5% sodium hydroxide solution (2 volume parts) and water (7 volume parts) was added Fremy's salt (1 part) at room temperature with stirring. After being stirred for 1 hour, the mixture was cooled to 0° C., acidified with cold dilute hydrochloric acid, and extracted with ethyl acetate. The extract was washed with water, dried over anhydrous sodium sulfate, and concentrated in vacuo. The resulting residue was subjected to column chromatography on silica gel and eluted with chloroform-methanol (20:1). The product was recrystallized from ethylacetate-hexane (1:2) to give 2,3,5-trimethyl-6-(5'-carboxy-1'-hydroxypentyl)-1,4-benzoquinone (formula I-3 wherein R=H3C, n=4, in the free form) (0.128 part) as brown needles melting at 130°-131.5° C.
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