CS232599B1 - A method for preparing 1,6-anhydro-β-D-glucopyranose - Google Patents

Abstract

The method for preparing 1,6-anhydro-O-glucopyranose, the essence of which consists in the fact that ££rob or cellulose is modified by cross-linking with 2-chloromethyoxyphane in an alkaline environment at pH 12 to 14 in the presence of sodium hydroxide or potassium hydroxide to a cross-linking degree of 0.01 to 0.1, and the thus cross-linked product is subjected to vacuum pyrolysis at pressure 1.3 to 5.3 nkPa and a temperature of the reaction zone of 150 to 220 °C for 15 to 60 minutes, while the gaseous products of pyrolysis are continuously vacuumed into a system of aqueous scrubbers, the contents of which are described in detail! three-stage purification; in the first stage, the aqueous content is shaken into chloroform or benzene, in the second stage, the aqueous solution is concentrated and precipitated with an excess of acetone, and in the third stage, the acetone filtrate is concentrated and allowed to crystallize the isoyl,6-anhydro-D-glucopyranose from acetone or ethyl alcohol. The invention has applications in the chemical, biochemical and pharmaceutical industries as well as in research.

Description

The invention relates to a process for the preparation of 1,6-anhydro- [beta] -D-glucopyranose,

The methods described to date for the preparation of 1, β-anhydro-D-glucopyranose, also called levoglucosan, are either unrepeatable or difficult to produce, based on the processing of the pyrolysis products of corn starch, potato starch and the like. cellulose £ M. Cerny, J. Stanek: Advanoes in Carbohydrate Chemistry 34, 23 (1977) J, or multistage syntheses [& Micheel, G. Baumj Chemische Berichte 88, 479 (1955)], starting from a bag of starting materials such as [J] - 1-fluoro, / d -1-azido or 4-phenoxy-1-D-glucopyranose and having also a time consuming and inefficient methods, providing the _t work with only small gram quantities yields, not exceeding 10% by weight calculated to the initial weight. the product (i.e. D-glucose) as indicated in the literature.

The above disadvantages are substantially eliminated by the process of preparing 1,6-anhydro-4-D-glucopyranose according to the present invention, which is based on the fact that <Z-1,4 (6) glucan in natural materials such as the starch or cellulose is first modified by crosslinking with 2-chloromethyloxirane in an alkaline medium (pH 12-14) in the presence of sodium or potassium hydroxide to a crosslinking degree of 0.01 to 0.1 and the crosslinked product thus obtained is subjected to vacuum pyrolysis for example. ¹ * pressure 1.33 to 5.33 bar and a temperature of the reaction zone of 150-220 ° C for 15-60 minutes, the gaseous pyrolysis products are continuously vacuum-stripped to a scrubbing system vodných-, the content of the subject, the three-step purification; in the first. step, the aqueous content is shaken

232 599 in chloroform or benzene, in the second step the aqueous solution is concentrated and precipitated with excess acetone, and in the third step the acetone filtrate is concentrated and crystallized by 1,6-anhydro-4-β-glucopyranose from acetone or ethyl alcohol.

The advantage of the proposed process is the perfect reproducibility, allowing the preparation of levoglucosan at least in larger to kilogram quantities in a crystalline state of high purity, in an efficient manner, with the possibility of recovering the recovered solvents used, which is important in particular for preparing larger quantities of the desired product. A further advantage of the proposed process is that it achieves substantially higher yields of the main product in crystalline form, ranging from 20 to 25% by weight based on the weight of the starting glucan.

Example 1.

1200 g of potato starch with a moisture content of 10 to 12% by weight are cross-linked in 2400 ml of 0.4% by weight aqueous sodium hydroxide solution, in which 6 ml of epichlorohydrin (1-chloromethyloxirane) are previously dissolved. Crosslinking is performed at 25 ° C for 12-16 hours (preferably overnight without stirring the reaction mixture). After completion of the crosslinking, 5 liters of 0.9 to 1.0% by weight aqueous sodium hydroxide solution are added to the reaction mixture while stirring, while the cross-linked starch gels. After gelation, the sodium hydroxide present is neutralized with an equivalent amount of hydrochloric acid and the excess solution is filtered off with suction. The moist starch is passed through a sieve with a mesh diameter of 2 to 3 mm and allowed to dry to obtain a uniform granule of optimum grain size for pyrolysis. Pyrolysis of 1200 g of Mashed Potato Starch at a pressure of 1.3 to 5.3 kPa and at a reaction zone temperature of 150 to 220 ° C for 30 minutes collects raw rain in an amount of 820 g (ie 68.5%) ), wherein the amount of non-combustible residue is 120 g (i.e. 10%). The contents of the water washers were transferred to a 5-liter separatory funnel and made up to 3000 ml with water. Water insoluble fractions of pyro4

The 232,599 lysates were extracted with chloroform (1 x 300 mL), with an aromatic substance having a total weight of 60 g (ie 5%) being passed into the organic solvent. The aqueous solution of the reaction mixture is concentrated to about 500 ml volume in a evaporator at 1.3 kPa. The concentrated volume is precipitated with acetone (about 2 liters), whereby the concomitant sugar is precipitated. in the amount of 85 g (ie 7%), and the presence of which prevents the crystallization of levoglucosan. The amount of refined pyrolysate obtained in this way is 580 g (ie 49%). After concentrating the acetone solution of the reaction mixture to 500 ml, the crude product 1,6-anhydro- [beta] -D-glucopyranose is crystallized in an amount of 250 g (i.e. 21%) by standing the residue at room temperature for 12 hours. Recrystallization of the crude product from ethyl alcohol gave a melting point of 180-182 ° C and an optical rotation of -66 ^° (HgO; c = 1).

Example 2

As described in Example 1, except that microcrystalline cellulose of polymerization stage 160 crosslinked with 2-chloromethyl oxirane in potassium hydroxide medium to a crosslinking degree of 0.1 is used. Pyrolysis of 500 g of the crosslinked microcrystalline cellulose in the above manner at 220 ° C for 15 minutes after treatment of the reaction mixture according to the procedure of Example 1 yielded 40 g of levoglucosan, i.e. crystallized from ethyl alcohol. with an 8% yield based on the starting product.

Example 3

As described in Example 1, except that corn starch crosslinked with 2-chloromethyl oxirane to a crosslinking degree of 0.01 is used. Pyrolysis 1200 g of the amount of corn starch thus crosslinked as described above. at 150 DEG C. for 45 minutes and extracting the aromatic portions of the reaction mixture into benzene, after working up the reaction mixture according to the procedure of Example 1, up to 300 g of crude product was obtained by crystallization from acetone.

232,599 1,6-anhydro- [beta] -D-glucopyranose duct, i. 25% relative to the starting product (maize starch).

Example 4

As in Example 1, except that in the purification stage of the pyrolysis condensates, these are taken up in benzene (instead of chloroform) and in the last step ethyl alcohol is used instead of acetone. The yields and properties of the main product are similar to those of Example 1.

The invention has applications in the chemical, biochemical and pharmaceutical industries, not only in the manufacture of self-resolving 1,6-anhydro-γ-D-glucopyranose, but also in the preparation of rare deoxy sugars (e.g. 4-deoxy-D-glucose, 4- deoxy-D-mannose, 3-deoxy-D-galactose and the like), rare amino sugars (e.g., 4-amino-4-deoxy-D-glucose and the like), various dianhydroderivatives of D-glucose, etc. Both levoglucosan and the above deoxy and amino sugars find use both as pure chemicals, suitable for metabolic studies and theoretical studies of carbohydrate chemistry and biochemistry, and also as products of importance in the medical and pharmaceutical industries.

OBJECT OF THE INVENTION

Claims (1)

232 599 Process for the preparation of 1,6-anhydro- [beta] -D-glucopyranose by vacuum pyrolysis of starch or cellulose, characterized in that the starch or cellulose is modified by fusing with 2-chloromethyl-oxirane in an alkaline medium at pH 12 to 14 in the presence of sodium or potassium hydroxide to a crosslinking degree of 0.01 to 0.1 and the crosslinked product is subjected to vacuum pyrolysis at a pressure of 1.3 to 5.3 kPa and a reaction zone temperature of 150 to 220 ° C for 15 to 60 minutes, the pyrolysis gas products being continuously evacuated to a water scrubber system, the contents of which were subjected to a three-stage purification step, in the first stage the aqueous content was shaken out in chloroform or benzene, in the second stage the aqueous solution was concentrated and precipitated with excess acetone; -anhydro- [beta] -D-glucopyranose from acetone or ethyl alcohol.