CS260392B1 - Method of preparation of aldoses - Google Patents

Abstract

The purpose of the method of preparing aldoses is to improve the methods of preparing aldoses, i.e. to simplify and economize these methods of preparation. The stated purpose is achieved by adding oxalic acid to the phenylhydrazone of aldose, benzaldehyde, ethanol, water and a molybdate compound in a molar ratio of molybdenum with oxidation state VI to oxalic acid of 1: at least 4 and allowing it to react at temperatures up to 100 °C. The method of preparing aldoses has applications in organic chemistry.

Description

The invention relates to a process for the preparation of aldoses.

Aldoses are epimerized in weakly acidic aqueous solutions in the presence of molybdenum ions to form an equilibrium mixture of C-2-epimeric aldoses [V. Bilik: Chem. sheets 77, 496 (1983)]. Molybdenum ions as a catalyst component are also used in the stereoselective hydroxylation of glycals to the corresponding aldoses with cis-arrangement of hydroxyl groups on the C-2 and C-3 [V] carbon atoms. Bílik: Chem Rumors 26, 76 (1972)], by oxidative decomposition of 1-deoxy-1-nitroalditols to the corresponding aldoses [V. White: Coll. Czechoslov. Chem. Commun. 39, 1 621 51974] and the oxidative degradation of aldose phenylhydrazones by the corresponding aldoses by one carbon atom below (V. Bilik. P. Biely, M. Matulova: Chem. Rev. 33, 782 (1979)]. Therefore, in the isolation of aldoses obtained by molybdenum-catalyzed reactions, molybdenum ions are not present, as are known methods for removing molybdenum ions on anion exchangers, the disadvantages of which are the large dilution of aldose solutions and the high energy consumption to thicken these solutions. is carried out by displacement with benzaldehyde [V. Bílik: Chem. Rev. 26, 183 (1972), V. Bílik: Coll. Czechoslov. Chem. ommun. 39, 1621 (1974)] The complete inhibition of molybdenum ion catalyzed aldose reaction has not been known.

The above drawbacks are substantially eliminated by the process of preparing aldoses, which comprises adding oxalic acid in the molar ratio of molybdenum to oxidation grade VI to oxalic acid 1: at least 4 and leaving it to the aldehyde, benzaldehyde, ethanol, water, and molybdenum compound. at temperatures up to 100 ° C. The advantage of the proposed method of preparing aldoses is that it is not necessary to remove molybdenum ions, most often by anion exchangers, followed by concentration by the solution, thus saving on wages, materials, energy and substantially saving the use of some equipment (evaporators, columns). Example 1

L-mannose phenylhydrazone 27 g (0.1 mole) mixture, 0.25 g (2.10 ~ 6 moles) hexaammonium heptamolybdate tetrahydrate, 0.71 grams (5.6.10-3 moles) of oxalic acid dihydrate (molar ratio of oxalic acid to molybdenum) 4: 1), 20.3 ml (0.2 mol) of benzaldehyde, 35 ml of 96 wt. ethanol and 190 ml of water are heated for 3 h at 90 ° C. Inhibition of L-mannose epimerization is determined by paper chromatography (WhatmanNo 1j using elution system A: acetone, 1-butanol and water 7: 2: 1 and elution system B: 1-butanol, ethanol and water 5: 5). 1: 4, with an elution time of 18 to 20 h and following detection with aniline hydrogen phthalate The chromatographic record shows the presence of L-mannose and the presence of L-glucose in the trace. 1.31 and in elution system B: 1.30 Example 2

The procedure is as in Example 1 except that phenylhydrazone D-galactose is used and the mixture is heated at 100 ° C for 2 h. The chromatographic data shows the presence of D-galactose and the absence of D-talose in trace amounts. Glucose mobility of 1.00 is for galactose in elution system A: 0.82 and in elution system B: 0.86, for talose in elution system A: 1.76 and in elution system B: 1.69 . In the Examples, epimerization inhibition temperatures of 90 and 100 ° C are given, but the epimerization is also inhibited at substantially lower temperatures, for example, when concentrating aldose solutions. Oxalic acid forms a stable complex with molybdenum ions, which inhibits aldose epimerization as well as substantial, longer time as described in the Examples. However, it is not effective to store aldose solutions at lower temperatures for longer periods, as aldose is a good nutrient for some microorganisms.

A method of preparing aldoses can be found widely in organic chemistry and biochemistry.

Claims (1)

SUBJECT A method of preparing aldoses from the corresponding phenylhydrazones by aldose by the action of benzaldehyde, characterized in that ynAsezic acid is added to the phenylhydrazone of aldose, benzaldehyde, ethanol, water and molybdenum compound in the molar ratio of molybdenum to oxidation grade VI to oxalic acid 1: at least 4. and allowed to react at temperatures up to 100 ° C.