DE644962C - Process for the preparation of 2-keto-1-gulonic acid - Google Patents

Description

It has been found that 2-keto-l-gulonic acid by direct oxidation of 1-sorbose can be obtained. For this purpose, 1-sorbose is treated in an aqueous solution Solution with a pn below 7 gradually with the 2 oxygen equivalents not essential excessive amount of oxidizing agent. To achieve good yields, it is advisable to to choose the conditions so that the oxidation does not exceed the desired level as far as possible Stage progresses what z. B. by dilution, gradual addition of the oxidizing agent, Keeping the temperature low and optionally catalysts can be achieved. To the separation of by-products To facilitate the procedure, the reaction can be carried out in two stages executes. In this case, the 1-sorbose is initially only oxidized to 1-guloson, the raw 1-guloson-containing mixture does not need to be processed into pure 1-guloson to become what is troublesome, whereas one can do it for the relief of the following Working up by neutralization with alkaline earths, removal of the majority of the Remove acidic by-products from water by distillation and treatment with alcohol. As a result, the majority of the acidic by-products as insoluble alkaline earth salts dejected. The crude 1-gulosone freed from acidic by-products can then be converted into 2-keto-igulonic acid in a second stage are oxidized. The reaction proceeds according to the following scheme:

CH ₂ OH

OH-C-H

I.
H - C - OH

OH —CH
I.

CH ₂ OH
1-sorbose

C = I -v OH - C-H

H - C - OH I.

OH-C - H!

CH ₂ OH 1-guloson COOH
I.

C = O
1
OH - CH

Η —C-OH

I 6ο

OH-C-H
!

CH ₂ OH
2-keto-l-gulonic acid.

A way similar to the embodiment just mentioned is already by Micheel recently and force has been described (Naturwissenschaften 22/1934 p. 205). The mentioned However, the authors produced the 1-guloson by cleaving the corresponding osazone

Process that is hardly technically feasible. The same is true of a method of manufacture of oonic acids from osones with bromine water (Biochem. Journal 207/1929 p. 217, 230). The present method differs from the known methods in that that 1-sorbose is either oxidized directly to 2-keto-l-gulonic acid, or that they are first oxidized to a 1-guloson-containing mixture and this raw Mixture, optionally after removal of acidic by-products, further oxidized.

The 2-keto-l-gulonic acid is said to be used for the production of 1-ascorbic acid (("-Vitamin) Find.

example 1

10 parts of 1-sorbose, and 1 part of ferrous sulfate are dissolved in 200 parts of water, mixed with 0.5 parts of 2-η sulfuric acid and in the solution in the course of about 4 hours while stirring and cooling to at most 30 ⁰ 63 parts of 3 ° / oiges Allowed hydrogen peroxide to flow in. After standing for 2 hours, the mixture is stirred with calcium carbonate until the reaction is neutral, the precipitate is filtered off with suction and the somewhat dark-colored solution is evaporated to a syrup in vacuo. The 1-guloson and unchanged 1-sorbose are extracted from this by treatment with alcohol. The precipitated salts are dissolved again with a little water to form a syrup and treated again with alcohol until they disintegrate into a powder. After removing the iron with hydrogen sulfide, the calcium with oxalic acid and the sulfuric acid with barium carbonate, the resulting 2-keto-l-gulonic acid can be obtained from the salts purified in this way by fractional crystallization of the quinine salts. When the aqueous solution is neutralized with quinine, the very sparingly soluble quinine salt of l-xylonic acid is obtained first. This shows a melting point of 233 to 234 ⁰ corr. Decomp. and an (α) '| = -156 ⁰ (c = 0.072 in water).

When the mother liquors are concentrated in vacuo, the Quinine salt of 2-keto-l-gulonic acid, which contains ι mol of water of crystallization, has a melting point from 155 to 156 ° corr. Decomp. and a

(α) ~ = -73.2 ° (c = 2.95 in water).

The solubility in water of 20 ⁰ is 4.42. ° /. ·

The alcoholic solution, which contains the 1-guloson, is strongly concentrated in a vacuum, the remaining syrup is diluted with a little alcohol and the unchanged sorbose is allowed to crystallize out if possible by standing for a long time. The crystals which have been centrifuged out sharply or which have been sucked off are washed with a little alcohol and can then be used for a new reaction. The solution running off is freed from alcohol under reduced pressure and the osone content is determined in a sample by titration using the cyanide method. The product contains an average of about 1.5 parts of Reinoson. It is then diluted with 150 parts of distilled water, 3 to 4 parts of precipitated barium carbonate are added and a solution of 1.1 parts of barium permanganate in the required amount of water is run in while stirring and cooling to -100, which is almost instantly decolorized. The mixture is then heated briefly until the precipitate can be easily filtered, filtered and the filtrate is concentrated to a small volume under reduced pressure. The addition of alcohol causes the barium salt of ketogulonic acid to precipitate; it is filtered off, washed with alcohol, dissolved in water and precisely broken down with sulfuric acid so that just a detectable trace of barium ion remains in the solution. After removing the barium sulfate by filtration, the mixture is concentrated in vacuo, and the ketogulonic acid crystallizes out of the syrupy residue, especially after seeding. If necessary, ¹ can also be purified beforehand using the sodium, potassium, quinine, morphine or codeine salts, which crystallize well and are also suitable for processing mother liquors.

B e i s ρ i e 1 2

1.8 parts of 1-sorbose, and 5.4 part of potassium persulfate are heated for several hours at 70 ⁰ in 50 parts of water, unresponsive to the solution to starch-iodide. A hot, aqueous solution of barium chloride is then added in slight excess, the barium sulfate which has precipitated is filtered off, the solution is evaporated at a low temperature in a vacuum and the hydrochloric acid is driven off by prolonged evacuation. The residue forms a crystalline mass which, in addition to unchanged 1-sorbose, contains 2-keto-l-gulonic acid. Further purification of the 2-keto-l-gulonic acid is carried out, w \ s described in Example. 1

B e i s ρ i e 1 3

2 parts of 1-sorbose are dissolved in 3 parts of water. Then, to the solution 1 part of nitric acid is added to the specific gravity of 1.4, and the solution was heated for several hours to about 70 ⁰ until no nitrous gases escape. Some lower nitrogen oxides or fuming nitric acid can be added to initiate the reaction. Vanadium compounds also have a strong effect

accelerating and allow the reaction temperature to be kept lower. The work-up happens as indicated in the example ι.

Claims (5)

Patent claims: 1. A process for the preparation of 2-keto-l-gulonic acid, characterized in that that one 1-sorbose in aqueous solution with a pn below 7 gradually with the amount of oxidizing agent not significantly exceeding 2 oxygen equivalents treated. 2. The method according to claim 1, characterized in that the oxidation in two Stages is carried out by first converting 1-sorbose to the 1-Guloson the necessary amount of oxidizing agent is treated and the resulting Mixture, optionally after removal of acidic by-products, with that corresponding approximately to one oxygen equivalent Amount of oxidizing agent, calculated on the 1-guloson present, is further oxidized. 3. The method according to claim 1, characterized in that the oxidizing agent Hydrogen peroxide is used in the presence of catalysts. 4. The method according to claim 1, characterized in that one is used as the oxidizing agent Hypohalides used. 5. The method according to claim 2, characterized in that one for the oxidation of the 1-guloson-containing mixture permanganate used.