JPS5811869B2 - Purification method of tocopherol - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying crude dl-α-tocopherol obtained by condensing trimethylhydroquinone with phytol, isophytol or phytyl halide. - dl characterized by decolorizing tocopherol by treating it with one or a mixture of zinc, iron or tin in the presence of a trace amount of acid;
-Regarding a method for purifying α-tocopherol.

As a method for producing dl-α-tocopherol, many methods are conventionally known in which trimethylhydroquinone and phytol, inphytol, or phytyl halide are condensed using an appropriate catalyst and solvent.

However, these methods have problems such as the need for a complicated purification step after the condensation reaction because the obtained dl-α-tocopherol contains coloring impurities.

That is, conventional purification methods such as high vacuum distillation and molecular distillation cannot separate the colored impurities mixed in dl-α-tocopherol.

Therefore, it is necessary to purify it by column chromatography or to adopt a production method that produces as little colored impurities as possible during the reaction.

As a method for producing α-tocopherol that does not produce coloring impurities, it is known to add metallic zinc to the reaction medium of phytyl chloride and trimethyl hydroquinone, as shown in Japanese Patent Publication No. 45-31662, for example. However, this method has disadvantages, such as preparing the raw material phytyl chloride by reacting inphytol with hydrochloric acid in advance, and generating a large amount of hydrogen chloride gas during condensation with trimedel hydroquinone. This is not an economical method.

Therefore, the feature of the present invention is that before the obtained crude dl-α-tocopherol is subjected to molecular distillation or high vacuum distillation, the crude dl-α-tocopherol is
The object of the present invention is to increase the purification yield and obtain highly pure dl-α tocopherol by carrying out a simple decolorization operation of l-α-tocopherol.

In detail, zinc, iron, or tin metal (often in the form of powder, granules, or flakes with a large surface area, and especially zinc powder) reacts with an acid to generate hydrogen when crude dl-α-tocopherol is obtained through a condensation reaction. , iron powder, and tin powder are preferred.

) and a trace amount of acid, such as acetic acid, hydrochloric acid, p-toluenesulfonic acid, sulfuric acid, ammonium chloride, etc. (acetic acid is particularly preferred for acetylation after decolorization).

), stirred in a solvent, and reductively decolored with nascent hydrogen.
The purpose is to enable the purification of l-α-tocopherol.

The free dl-α-tocopherol thus obtained is converted into a stable acetyl form, and then subjected to molecular distillation and high vacuum distillation to produce colorless purified dl-α-tocopheryl acetate.

Furthermore, by providing a method for purifying crude dl-α-tocopherol according to the present invention, dl-α-tocopherol can be produced using the most economical process without paying attention to coloration.

When purifying the obtained a-α-tocopherol, the d
It is possible to adjust the amount of zinc powder, tin powder, iron powder, etc. added depending on the coloring property of l-α-tocopherol.In carrying out the present invention, trinotylhydroquinone and inphytol, phytol or phytyl are used. Crude a-α-tocopherol, which is a condensation product of halide, is dissolved in a solvent such as benzene, toluene, xylene, petroleum ether, petroleum benzine, ligroin, ethyl acetate, improvyl acetate, isobutyl acetate, ether, etc. in a nitrogen gas stream. 0.01 to 1.0 mol of metal bed is added to 1 mol of crude dl-α-tocopherol.

In this case, preferably 0.05 to 0.5 mol of zinc powder is suitable.

Furthermore, add 0.1 to about 1 to 1 liter of acid and raise the temperature to -10 to 150℃.
, preferably at room temperature to solvent reflux temperature for 1 to 10 hours.

In some cases, the reaction may be accelerated by adding a small amount of water.

After the reaction, 3 moles of acetic anhydride and 0.01 mole of sodium acetate or 0.01 mole of pyridine are added and heated under reflux for 1 to 5 hours to complete acetylation.

After sequentially washing with water, water-methanol, dilute alkaline water-methanol, and water-methanol according to a conventional method, the mixture is concentrated under reduced pressure to obtain the desired colorless and transparent dl-α-tocopheryl acetate.

Yield is quantitative.

In some cases, purified a-α-tocopheryl acetate can be obtained with a distillation yield of 90% or more by performing vacuum distillation or molecular distillation.

In the examples, E+t5mμ is 415mμ of a 40% ethanol solution of dl-α-tocopherol acetate.
It represents the absorbance at μ.

Example 1 21.5 g of yellowish brown crude rho-α-tocopherol (purity 93%; 0.047 mol; E415m of dl-α-tocopherol acetate obtained by acetylating this)
0.612) was dissolved in 50 ml of ligne in a nitrogen gas stream, and 0.3 g (0,0046 mol) of zinc powder and 5 ml of acetic acid were dissolved.
Add m1 (0,087 mol) and stir at room temperature for 2 hours.

During this time, the reaction solution changes from yellowish brown to pale yellow.

Next, 5.1 g of acetic anhydride and 0.0 g of sodium acetate were added. ! 1 was added, and the mixture was stirred and refluxed for 3 hours.

After the reaction, pour into ice water, extract and wash, neutralize NaOH with aqueous solution, extract and wash with water, concentrate under reduced pressure, and distill under reduced pressure.
Take the po, os fractions at 200-220°C.

The result was a colorless and transparent purified a-α-tocopheryl acetate 19.5.1 (purity of 98% or more; E415mμ=0.
191) was obtained.

Example 2 21.5 g of yellowish brown crude rho-α-tocopherol (purity 93%; 0.047 mol; E41.rr of d/-α-tocopherol acetate obtained by acetylating this)
L=0.612) was dissolved in isobutyl acetate 50- in a nitrogen gas stream, and 0.3 g (0,0046 mol) of zinc powder was added.
5 mJ (o, o 87 mol) of acetic acid and 0.1 ml of water were added, and the mixture was stirred at room temperature for 2 hours.

During this time, the reaction solution changes from yellowish brown to slightly yellow.

Next, 5.1 g of acetic anhydride and 0.5 g of sodium acetate are added, and the mixture is stirred and refluxed for 3 hours.

After the reaction, it was poured into ice water, extracted and washed, neutralized with NaOH aqueous solution, extracted and washed with water, concentrated under reduced pressure, and distilled under reduced pressure.
) plM, the fraction from 5200 to 220°C was taken.

This product is colorless and transparent purified a-α-tocopheryl acetate, 19.85g (purity of 98% or more”E415
77L, cg20.153) was obtained.

Example 3 Yellow-brown crude rho-α-tocopherol 21.5,9 (purity 93%; 0.047 mol: E4157r of a-α-tocopherol acetate obtained by acetylating this)
L20.612) toluene 50% in a nitrogen gas stream
Dissolve in WLl, add 0.3 g (0,0025 mol) of metal soot powder, 5 ml (0,087 mol) of acetic acid and 0.1 ml of water, and stir at room temperature for 2 hours.

During this time, the reaction solution changes from yellowish brown to yellow.

Next, 5.1 g of acetic anhydride and 0.5 g of sodium acetate.
! Add li' and stir and reflux for 3 hours.

The reaction is then carried out in the same manner as in Example 2.

t) Take a fraction of po, o3200 to 220°C.

This product is colorless and transparent purified dl-α-tocopheryl acetate, and is 18.48! ! (Purity 98% or more; E4
15 m, a2 0.221) was obtained.

Example 4 Trimethylhydroquinone 76.109 (0.50 mol), ZnC6274.97 g (0.55 mol), CAC
5,00 g (0,053 mol) of H2COOH was dissolved in 300 TILl of isobutyl acetate in a nitrogen gas stream, and Infitol 156.06.9 (0,53 mol) was added dropwise over 1 hour while stirring and refluxing, followed by further stirring and refluxing. for 2 hours.

Furthermore, water produced during the reaction is distilled off azeotropically, and isobutyl acetate is recycled.

After the reaction, the mixture is extracted and washed three times with 100 ml of 50% methanol water, and twice with 10,077 Il of water.

50 ml (0.87 mol) of acetic acid and 13.11 (0.20 mol) zinc dust are added to the isobutyl acetate solution and stirred at room temperature for 2 hours.

After stirring, the mixture was heated to reflux and water was distilled off by azeotropy. After dehydration, 153.14 g of acetic anhydride and 12.30 g of sodium acetate were added, and the mixture was heated to reflux for 4 hours to complete acetylation.

The reaction solution is poured into ice water, extracted and washed, neutralized with an aqueous NaOH solution, and extracted and washed with water.

Concentrate under reduced pressure and distill under reduced pressure. bpo, os200-22
213 g of a 0°C fraction was obtained.

This product was colorless and transparent dl-α-tocopheryl acetate (E+t5m11=0.142).

Claims (1)

[Claims] 1. A method for purifying dl-α-tocopherol, which comprises decolorizing crude dl-α-tocopherol by treating it with one or a mixture of zinc, iron, or tin in the presence of a trace amount of acid.