Pyridine → Alpha-Tocopherol Acetate

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반응 단계

The crude α-tocopherol is treated with 25.0 g of acetic anhydride (corresponding to 244.9 mmol), 25.0 g of pyridine (corresponding to 316.1 mmol) and 1.0 g of 4-dimethyl-aminopyridine (corresponding to 8.2 mmol; catalytic amount) and stirred for one hour at room temperature. The reaction mixture is poured on to 100 g of ice/water (about 1:1), stirred for 30 minutes, treated with 250 ml of n-hexane and washed in succession twice with 150 ml of water each time, twice with 100 ml of 2N sulphuric acid each time, with 150 ml of water, with 150 ml of saturated sodium bicarbonate solution and three times with 150 ml of water each time. Thereafter, the mixture is dried over 3 g of anhydrous magnesium sulphate for 10 minutes while stirring. After filtration, distillation of the solvent at 400 mbar and a bath temperature of 60° C. and subsequent drying for 30 minutes at 15 mbar and a bath temperature of 70° C. there are obtained 29.26 g of α-tocopherol acetate as a yellow oil, α-tocopherol acetate content (GC, internal standard squalane) 87.5%, chemical yield (α-tocopherol acetate) 93.1%. This crude acetate is distilled in a bulb tube oven (250° C./10-1 mbar). There are obtained 26.25 g of α-tocopherol acetate as a slightly yellowish oil which crystallizes slowly upon standing at room temperature. α-Tocopherol acetate content (GC, internal standard squalane) 96.2%, chemical yield 91.8%; stereo-chemical purity: 99.6% R,R,R-α isomer (HPLC of the methyl ether derivative on Chiracel OD, n-hexane); the product is identical with α-tocopheryl acetate according to 1H-NMR, IR, MS and microanalytical data.

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