[H-].[Al+3].[Li+].[H-].[H-].[H-].[OH:7][C:8]1[C:22]([CH3:23])=[C:21]([CH3:24])[CH:20]=[C:19]([CH3:25])[C:9]=1[C:10]([CH2:12][CH2:13][CH2:14][CH2:15][C:16]([OH:18])=[O:17])=[O:11].Cl>O1CCCC1>[OH:11][CH:10]([C:9]1[C:19]([CH3:25])=[CH:20][C:21]([CH3:24])=[C:22]([CH3:23])[C:8]=1[OH:7])[CH2:12][CH2:13][CH2:14][CH2:15][C:16]([OH:18])=[O:17]To a well stirred suspension of lithium aluminum hydride (2 parts) in dry tetrahydrofuran (50 volume parts) was added a solution of 5-(2'-hydroxy-3',4',6'-trimethylbenzoyl)pentanoic acid (formula II-1 wherein R=H3C, X=H, Y=OH, n=4, in the free form) in dry tetrahydrofuran (10 volume parts) at room temperature. After being stirred under reflux for 2 hours, the mixture was cooled to 0° C., acidified with cold dilute hydrochloric acid, and extracted with ethyl acetate. The ethyl acetate 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 carbon tetrachloride-acetone (5:1). From the 1st fraction, 6-hydroxy-6-(2'-hydroxy-3',4',6'-trimethylphenyl)hexanoic acid (formula II-3 wherein R=H3C, X=H, Y=OH, n=4, in the free form) (0.45 part) was obtained as colorless needles melting at 165°-166° C.
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