RU2440362C1 - Method of producing d(+) glucosamine hydrochloride - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: method involves preliminary acetylation of chitin with acetic anhydride, washing and drying the acetylated chitin in order to reduce degree of deacetylation thereof and, as a result, increase output of the desired product - D(+)-glucosamine hydrochloride when obtaining said product through hydrolysis of acetylated chitin with concentrated hydrochloric acid while heating, followed by evaporation, crystallisation, separation, washing and drying the desired product.

EFFECT: high output of the desired product while maintaining its high quality; method is more environmentally friendly since pre-treatment of chitin reduces the amount of processing wastes.

1 cl, 2 ex

Description

The invention is intended for use in medicine, veterinary medicine, cosmetics and relates to a method for producing amino sugars used as chemical reagents and drugs.

A known method of producing D (+) - glucosamine hydrochloride, which consists in the hydrolysis of chitin in concentrated hydrochloric acid with stirring and heating in a boiling water bath for 2.5 hours. The ratio of the mass of chitin and the mass of hydrochloric acid with a specific gravity of 11.18 g / cm ³ is 1: 5.9. At the end of hydrolysis, water (with a ratio of chitin: water 1: 5) and activated carbon (with a ratio of 1: 0.1) are added to the solution. The mixture was decolorized with stirring at 60 ° C for 1 h and filtered. If necessary, discoloration of the hydrolyzate is repeated. The purified hydrolyzate is evaporated in vacuo at 50 ° C to 2-4% of the initial solution of 10-15 ml.

Crystals of D (+) - glucosamine hydrochloride are washed with ethanol and then dried. The product yield is 60-70% (Syntheses of organic preparations. Collection 4 / Transl. From English. - M.: Publishing House of Foreign Literature, 1953. - 660 p. S.140-141). (Purchase E.R., Braun C.E. D-Glucosamine hydrochloride // Organic Syntheses. - 1946. - Vol. 26. - P.36-37).

There is also known a method for producing D (+) - glucosamine hydrochloride by dissolving chitin in excess of concentrated hydrochloric acid and subsequent evaporation of the solution to form a slurry. The resulting suspension is diluted with water at a ratio of chitin and water of 1: 2.5 and the solution is decolorized with activated carbon for 4-5 minutes. Coal is separated by filtration, the filtrate is evaporated in vacuo before crystallization begins, cooled, and the precipitated crystals are separated by filtration.

Next, the crystals are washed with cold water, alcohol and dried. Further purification of D (+) - glucosamine hydrochloride is carried out by recrystallization from hot 80% ethanol.

The product yield is 70-74% (Markov S. Method for receiving glycosamine hydrochloride // Pharmacy (Balg.) - 1964. - T.14, No. 2. - S.30-32).

Close to the proposed is the method according to the invention (Kazakov A.L., Samokish I.I., Kompantsev V.A., Lobova E.I., Novikov V.Yu., Orlova T.A. Pyatigorsk Pharmaceutical Institute; NPO Sevrybtekhtsentr ", Murmansk. Method for the production of glucosamine hydrochloride with anti-arthritic activity: Patent RU 2038095. - MKI ⁶ AK61/60. - Application 05.09.1991; No. 5037787/14; Publishing date 27.06.1995. - Bull. No. 18 ), in which, to obtain the target product, chitin hydrolysis is carried out with concentrated hydrochloric acid (1:10) for 2 hours at a temperature of a water bath of 75 ° C, followed by dilution we take the hydrolyzate with water and combine the hydrolysis and purify it with activated carbon at 60 ° C, evaporate the hydrolyzate in vacuum at a temperature not exceeding 60 ° C to a residual liquid volume of 15% of the initial amount of hydrochloric acid and isolate the target product by crystallization from an aqueous acidic solution with stirring.

The precipitate D (+) - glucosamine hydrochloride is separated and washed with 96% alcohol to a white color, dried at a temperature not exceeding 60 ° C.

The yield of the target product is 69% when the content of the main substance D (+) - glucosamine hydrochloride is 99.4-99.6% by chloride ion and not less than 99% by the Elson-Morgan method.

There is also an improved method that excludes the use of activated carbon (Novikov V.Yu., Ivanov A.L., Atlant-SIM-Victor company. Method for producing D (+) hydrochloride - glucosamine: RF Patent 2042685, MKI ⁶ C07H 5/06 , СВВ 37/08. - Declared 02.11.92; No. 92003453/04; Published on 08.27.95. - Bull. No. 24).

Crustacean shell chitin is dissolved in concentrated hydrochloric acid 30-37%, heated in a boiling water bath for 45-120 min at a ratio of the mass of chitin and the mass of hydrochloric acid (1: 2) - (1: 4).

Within 5-10 minutes after the start of heating, chitin is dissolved in boiling hydrochloric acid, then the solution is kept until the chitin is completely hydrolyzed, the reaction mixture is cooled to room temperature (10-20 ° C) and left at this temperature for crystallization of D (+) - glucosamine hydrochloride for 8-48 hours

The precipitated dirty product is separated by decantation, filtration or centrifugation at room temperature. The precipitate is washed with an organic solvent (for example, ethyl or isopropyl alcohol, acetone, etc.) with a mass ratio of chitin and solvent (1: 5) - (1: 3), the washed precipitate is dissolved with stirring in water at a temperature of 50-80 ° С at the ratio of the masses of chitin and water (1: 2) - (1: 3).

The solution is filtered (centrifuged), evaporated in vacuum to 5-10% of the original volume at a temperature in the solution of not more than 60 ° C.

Crystals of D (+) - glucosamine hydrochloride are separated and washed with an organic solvent in portions 2-4 times. Rinsing is carried out to a pH of the washing solution of at least 2-3 on universal indicator paper.

The washed crystals of D (+) - glucosamine hydrochloride are dried in air at room temperature for 4-24 hours, and then in a drying device at a temperature not exceeding 60 ° C.

This method allows to exclude the use of activated carbon, to carry out the process without filtering hot hydrochloric acid solutions and without the expensive operation of evaporating concentrated hydrochloric acid. The described method is close to the claimed.

The absence of losses of the target product on activated carbon allows to increase the yield of D (+) - glucosamine hydrochloride to 70-76%.

All of the above methods for producing D (+) - glucosamine hydrochloride include hydrolysis of chitin with hydrochloric acid by heating, evaporation, crystallization, separation, washing and drying of the target product, while the yield of the finished product does not exceed 60-76%, which is not enough, since this the result can be improved.

Chitin is usually used as a raw material, which is obtained by a technology involving deproteinization with a hot alkali solution (usually 4% NaOH) and at room temperature a solution of mineral acid (usually 3.5-7% Hcl).

The analysis of chitin samples obtained in this way, and the known data on the same analysis presented in the scientific literature, show that such chitin has a deacetylation degree of about 15%.

This is due to the fact that in the process of obtaining the product during both alkaline and acid treatment, hydrolysis of amide bonds occurs, causing deacetylation.

It is also known that the glycosidic bonds at the second carbon atom of the deacetylated monomer unit of the partially deacetylated chitin (or chitosan) undergo acid degradation and depolymerization at a rate several times lower than the same bonds at the acetylated unit, due to the fact that the amino group is in position 2, positively charged under conditions of acid-catalyzed hydrolysis, lowers the electron density at the glycoside center, destabilizing carbocatins, shifting the equilibrium towards the initial state an event.

On the other hand, acetylation of the amino group at the second carbon atom accelerates the hydrolysis of glycosides by increasing the electron density and anchimeric assistance. This stabilizes carbocatins, which leads to an increase in the likelihood of their dissociation and, consequently, an increase in the rate of cleavage of the glycosidic bond (Komano, T. Studies on the chemical structure of mucopolysaccharides // Thesis or Dissertation. - Kyoto University, 1962. - 112 p. Varum KM, Ottoy MH Smidsrod O. Acid hydrolysis of chitosans // Carbohydrate Polymers. - 2001. - Vol.46, No.1. - P.89-98).

We found that the rate of destruction sharply decreases with increasing initial degree of chitin deacetylation (Novikov V.Yu. Acid hydrolysis of chitin and chitosan // Journal of Applied Chemistry. - 2004. - Vol.77, No.3. - P.490-493) . This leads to an increase in the yield of by-products and a decrease in the yield of the monomer D (+) - glucosamine.

The considered mechanism suggests two ways to increase the yield of the target product: suppressing the deacetylation reaction in an acidic medium or reducing the initial degree of chitin deacetylation.

The first method is practically impossible in an acidic environment in which amide bonds are easily cleaved in the presence of protons (acid catalysis).

The second way was successfully used by us to improve the method of obtaining the target product - D (+) - glucosamine hydrochloride.

The proposed method involves the preliminary acetylation of chitin with acetic anhydride, washing and drying acetylated chitin in order to reduce its degree of deacetylation and, as a result, increasing the yield of the target product - D (+) - glucosamine hydrochloride when it is obtained by hydrolysis of acetylated chitin with concentrated hydrochloric acid by heating followed by evaporation, crystallization, separation, washing and drying of the target product.

According to the proposed method, 1 part (100 g) of chitin for acetylation is poured into 10 parts (1 l) of a 20% solution of acetic anhydride in ethanol, thoroughly mixed for 2-3 hours and left at 4 ° C for 24 hours with periodic stirring . At the end of the reaction, 20 parts (2 L) of water are added to the solution, the solution is adjusted to pH 7 with 1N. NaOH, filtered and washed several times with acetylated chitin with distilled water. The resulting acetylated chitin is pre-dried at a temperature not exceeding 60 ° C. After acetylation, the degree of deacetylation of chitin decreases and ranges from 1 to 3%.

The degree of acetylation was determined by IR spectrophotometry (Chebotok E.P., Novikov V.Yu., Konovalova I.N. Effect of crystallinity of chitin and chitosan on the kinetics of alkaline deacetylation // Journal of Applied Chemistry. - 2007. - T.80, No. 10 - S.1724-1729).

The subsequent receipt of the target product - D (+) - glucosamine hydrochloride from acetylated chitin can be carried out by the methods described above, including acid hydrolysis by heating (analogues of the proposed method). In this case, for example:

- according to the invention (US Pat. No. 2038095), including hydrolysis of chitin with concentrated hydrochloric acid when heated, the addition of activated carbon, filtration, evaporation, washing and drying, the yield of the target product increased from 69% when the content of the main substance D (+) - glucosamine hydrochloride 99 , 4-99.6% to 81% at the same product purity;

- according to the invention (US Pat. No. 2042685), including hydrolysis with hydrochloric acid when heated, cooling and crystallization, filtering, washing with ethanol, dissolving and filtering, evaporation, washing, drying, the yield of the target product increased from 70-76% to 87%, mass its share in the product was also 99.5-99.9%.

Studies have shown that pre-acetylation of chitin with acetic anhydride to produce D (+) - glucosamine hydrochloride by known methods, including hydrolysis of chitin with concentrated hydrochloric acid when heated, can increase the yield of the target product from 60-76% to 81-87% by reducing the degree of deacetylation hydrolyzed chitin. Thus, the technical result of the invention is a significant increase in the yield of the target product while maintaining its high quality.

Examples of the method.

Example 1

In a round bottom flask with a capacity of 4 l with a stirring device, 1 l of a 20% solution of acetic anhydride in ethanol was poured, cooled to 4 ° C, and 100 g of chitin was added with stirring. The mixture was continuously stirred for 3 hours, and then left at 4 ° C and periodically stirred for 24 hours

After the completion of the reaction, 2 L of distilled water was added to the mixture with stirring and neutralized with 1 N. sodium hydroxide solution to pH 7.

The precipitate of acetylated chitin was separated by vacuum filtration on a Buchner funnel through 1-2 layers of filter paper, washed 2-3 times with distilled water to a filtrate pH of at least 6.5.

The resulting precipitate was dried in air at a temperature of 20-25 ° C, and then in an oven at a temperature not exceeding 60 ° C.

Dried acetylated chitin was loaded into a 2 L round-bottom flask, and 1000 g (847.5 ml) of concentrated hydrochloric acid (d = 1.18 kg / m ³ ) were poured at room temperature (US Pat. 2038095).

The flask with reflux condenser and stirrer was placed in a water bath with a temperature of 75 ° C. After complete dissolution of chitin, hydrolysis was carried out at a temperature of 75 ° C and stirring for 120 min.

After hydrolysis was completed, 500 ml of distilled water (1: 5 chitin: water) with a temperature of 80 ° С, 50 g of activated carbon (1: 0.5 chitin: charcoal) were added to the flask with the reaction mixture, and the mixture was stirred at a temperature of 60 ° С for 2 h to clean the hydrolyzate.

The hot solution was filtered through 4 layers of filter paper on a Buchner funnel under vacuum. At the end of the filtration, the coal was washed on the filter with hot (70 ° C) distilled water 500 ml (1: 5 chitin-water). Wash water was combined with the filtrate, which should be colorless or have a weak greenish-yellow color.

Then the purified solution was evaporated in vacuo on a rotary evaporator IR-1M at a temperature in the solution of 40-50 ° C by 85%. The suspension was cooled to a temperature not exceeding 4 ° C, kept for 8 hours until the dissolved product crystallized completely.

The obtained crystals were washed with 96% ethyl alcohol in portions 3-4 times until white. The total amount of alcohol per rinse is 300 ml (240 g).

The washed crystals were dried first in air at room temperature for 3 hours, and then in an oven at 60 ° C for 2 hours.

Received 81 g of D (+) - glucosamine hydrochloride. The yield of the target product was 81%.

Example 2

Acetylated chitin was obtained from 100 g of chitin, as described in example 1.

A portion of the dried acetylated chitin (40 g) was loaded into a 500 ml round bottom flask, 120 g (101.7 ml) of concentrated hydrochloric acid (d = 1.18 kg / m ³ ) were poured at room temperature (US Pat. No. 2042685).

The flask with reflux condenser and stirrer was placed in a boiling water bath. After 5-10 minutes, chitin was completely dissolved in boiling acid. With stirring, the rest of acetylated chitin (about 60 g) was added to the flask. After complete dissolution of chitin, hydrolysis was carried out at a boiling point of a mixture of 94-96 ° C and stirring for 120 minutes.

After hydrolysis, the flask with the reaction mixture was cooled to room temperature and left to crystallize for 18 hours.

The precipitate of dirty glucosamine hydrochloride was separated from the solution by filtration under vacuum on a Buchner funnel through 5 layers of filter paper.

The precipitate was washed in portions (4 times) with ethyl alcohol. 200 ml (160 g) of alcohol were used for washing.

The washed precipitate of the dirty product was dissolved in 200 cm ^{3 of} hot distilled water with a temperature of 50 ° C. The hot solution was filtered through 2 layers of filter paper on a Buchner funnel under vacuum.

Then the pure solution was evaporated under vacuum on a rotary evaporator IR-1M at a temperature in the solution of 40-50 ° C by 95%. The suspension was cooled to room temperature.

The resulting crystals were washed with ethyl alcohol in portions 4 times. The total amount of alcohol per rinse is 200 ml (160 g). The washed crystals were dried first in air at room temperature for 3 hours, and then in an oven at 60 ° C for 2 hours.

Received 87 g of D (+) - glucosamine hydrochloride. The yield is 87%.

The obtained D (+) - glucosamine hydrochloride - odorless white crystalline powder, non-hygroscopic, residual moisture 0.5% ash residue less than 0.1%. The decomposition temperature (blackening of the sample) 195-200 ° C, the pH of an aqueous 20% solution at 20 ° C 3.5-4.5 units.

Mass fraction of D (+) - glucosamine hydrochloride in the product obtained by the proposed method was 99.5-99.9%.

The mass fraction of the main substance in the product was determined by two methods: titration of hydrogen chloride bound to the molecule D (+) - glucosamine, sodium hydroxide solution with registration of changes in pH or conductivity of the solution; determination of the mass fraction of total nitrogen by the Kjeldahl method. Both methods gave consistent results.

Identification was carried out by infrared spectroscopy.

The identification and purity of the finished product was determined by high performance liquid chromatography.

As a standard, a preparation was used according to TU 6-09-05-936-78, D (+) - pure glucosamine hydrochloride qualification.

The obtained results confirm that the preliminary treatment of chitin by acetylation with acetic anhydride to reduce the initial degree of chitin deacetylation when producing D (+) - glucosamine hydrochloride by known methods, including hydrolysis of chitin with concentrated hydrochloric acid when heated, can significantly increase the yield of the target product from 60- 76% to 81-87%. At the same time, the quality of the product remains the same high.

In addition, the proposed method is more environmentally friendly, since pre-treatment of chitin can reduce the amount of processing waste up to 11-14%.

Claims (1)

A method of producing D (+) - glucosamine hydrochloride by hydrolysis of chitin with concentrated hydrochloric acid while heating to isolate the target product, including evaporation, crystallization, separation, washing and drying of the target product, characterized in that chitin is pretreated before hydrolysis of chitin with concentrated hydrochloric acid by acetylating with acetic anhydride; washing and drying acetylated chitin.