[CH2:1]([O:3][C:4](=[O:15])[CH:5]=[C:6]([CH3:14])[CH:7]=[CH:8][CH:9]=[C:10]([CH:12]=[O:13])[CH3:11])[CH3:2].[BH4-].[Na+].Cl>C(O)C>[CH2:1]([O:3][C:4](=[O:15])[CH:5]=[C:6]([CH3:14])[CH:7]=[CH:8][CH:9]=[C:10]([CH3:11])[CH2:12][OH:13])[CH3:2]36 g. of 7-formyl-3-methyl-octa-2,4,6-trien-1-oic acid ethyl ester are dissolved in 600 ml. of absolute ethanol. The solution is treated portionwise with 1.8 g. of sodium borohydride. The mixture is stirred for 2 hours at 10° C., then poured onto ice water and 3n aqueous hydrochloric acid and extracted with ether. The ether extract is washed successively with water, a saturated aqueous sodium bicarbonate solution and once more with water, dried over sodium sulfate and evaporated. There is obtained 8-hydroxy-3,7-dimethyl-octa-2,4,6-trien-1-oic acid ethyl ester, which is processed further as follows:
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