MXPA98001961A - Procedure for the preparation of asocorb monophosphates - Google Patents

Abstract

A process for the preparation of alkali metal and alkaline earth metal salts of L-ascorbic acid 2-monophosphate comprises reacting a 2-polyphosphate of L-ascorbic acid under alkaline conditions with an alkali metal or alkaline earth metal salt of L-ascorbic acid. -ascorbic in concentrated aqueous solution, the quantities of the salt of L-ascorbic acid and the alkaline earth metal hydroxide used as the base being arranged, so that the pH value of the reaction medium is maintained in the range of about 8 to about 11 and a stepped transfer of, in each case, a phosphate group of the polyphosphate to the salt of the L-ascorbic acid takes place until essentially the polyphosphate is consumed and only 2-monophosphate of the L-ascorbic acid is present. Preferably, the L-ascorbic acid 2-polyphosphate is produced in situ and calcium hydroxide is used as the base. Independently that if L-ascorbic acid 2-polyphosphate is produced separately or in situ, sodium trimetaphosphate is preferably used as the phosphorylating agent. Another aspect of the present invention comprises spraying the mixture obtained after completion of the cooling and dilution reaction to an appropriate viscosity. The product of the process according to the invention is suitable as an additive for human and animal foods, it is especially stable against oxidative and thermal degradation and has an especially high content of L-ascorbic bis-a-bis-polyphosphate monophosphate, and therefore it is mainly employment, preferably for the nutritional enrichment of fishing feed

Description

PROCEDURE FOR THE PREPARATION OF ASCORBILO MONOPHOSPHATES FIELD OF THE INVENTION The present invention relates to a novel process for the preparation of alkali metal and alkaline earth metal salts of L-ascorbic acid 2-monophosphate from an L-ascorbic acid salt and an alkaline earth metal hydroxide as the base.

BACKGROUND OF THE INVENTION As is known, ascorbic acid (vitamin) and its salts are used as additives for human and animal foods. However, the ascorbic acid itself is sensitive to temperature and oxidation and decomposes to a considerable extent, for example, in the production and storage of enriched fish feed and therefore is lost. The ascorbic acid phosphates in particular are, as is known, forms of ascorbic acid which are protected against oxidative and thermal degradation and consequently and mainly are used for the nutritional enrichment of fish feed. With the use of ascorbic acid phosphate, which are substantially more stable than ascorbic acid, the problem of decomposition is almost completely eliminated REF: 26965 and the ascorbic acid, which is active, for example, against scurvy in fish and cámbaros, is released in the host organism by the action of the enzymatic phosphatase. Two fundamentally different methods have had significance for the phosphorylation of ascorbic acid, ie phosphorylation using phosphorus oxychloride (as described, for example, in European patents 388,869 and 582,924, as well as in US Patent 4,179,445) and phosphorylation using polyphosphate, for example patents sodium trimetaphosphate (see, for example, U.S. Patents 4,647,672 and 5,110,950) by phosphorylating an L-ascorbic acid salt under basic conditions in both cases. The first process provides ascorbic acid 2-monophosphate as the main product and as by-products, mainly 3-phosphate of ascorbic acid and 2-pyrophosphate as well as bis (ascorbic acid) -2,2 'disphosphate [see C.H. Lee et al., Carbohydrate Res. 67, 127-138 (1971)]. The reaction products require complicated purification and can not be converted in a simple manner, for example by spray-drying the entire reaction mixture, into a product that can be marketed directly. For these reasons phosphorylation using phosphorus oxychloride is a procedure that has little attractive economically and ecologically. Alternative methods, that is, phosphorylation using polyphosphates, provides ascorbic acid 2-polyphosphate as the primary product, for example ascorbic acid 2-triphosphate when sodium trimetaphosphate is used. The ascorbic acid 2-polyphosphates can be degraded to the monophosphate with an excess of base. The ratio of ascorbic acid 2-monophosphate to ascorbic acid 2-diphosphate and higher phosphates is influenced by the amount of base used and the other reaction conditions. A disadvantage of this method is that a very large amount of a phosphorylating agent is required, for example at least 1 mole of sodium trimetaphosphate per mole of ascorbic acid. Further, when it should contain relatively little ascorbic acid polyphosphates and more than 2-ascorbic acid monophosphate, a large amount of base, for example calcium hydroxide, can be used. Thus, the product contains a large amount of inorganic phosphates; the content of equivalents of ascorbic acid in a dry product amounts to a maximum of about 25% by weight. The course of the process described in US Patent 5,110,950, while being used for the preparation of monophosphate, will be apparent from Reaction Scheme 1 below, in where, for the purpose of a clear and simple presentation, sodium ascorbate, sodium trimetaphosphate (the preferred phosphorylating agent) and calcium hydroxide (base) are used. Reaction scheme 1 + 1/2 Ca (0H) 2 - H20 Ca2 + + 1 Ca (0H) 2 - H20 NaCaP04 + 1 Ca (OH) 2 - H20 + NaCaP04 In this process sodium ascorbate is reacted with sodium trimetaphosphate in a molar ratio of 1: 1 under the influence of a total of 2.5 mol of calcium hydroxide in order to produce 1 mole of ascorbic acid 2-monophosphate after three stages. In this way, two moles of sodium calcium phosphate are released whose presence in the overall product is seen as a disadvantage. It has now been found that by using polyphosphate phosphorylation agents, for example sodium trimetaphosphate, alkali metal and alkaline earth metal salts of initially formed L-ascorbic acid 2-monophosphate can also be prepared, and then reacted under specific alkaline conditions with a solution concentrated salt of an alkali metal or alkaline earth metal salt of L-ascorbic acid, whereby in each case, a stepwise transfer of a phosphate group takes place from the polyphosphate to the salt of L-ascorbic acid in the course of the reaction until essentially the polyphosphate has been used and only 2-monophosphate salt of L-ascorbic acid is present. With these means they can be reduced drastically the required amounts of phosphorylating agents and base and the major disadvantages of the known processes can be eliminated. The process according to the invention for the preparation of alkali metal and alkaline earth metal salts of L-ascorbic acid 2-monophosphate of the general formula wherein each M + means alkali metal binding or the alkaline earth metal binding equivalent; comprises reacting a 2-polyphosphate of L-ascorbic acid of the general formula where M + has the meaning given before and n means an integer from 2, - under alkaline conditions with an alkali metal or alkaline earth metal salt of L-ascorbic acid of the general formula where M + has the meaning indicated above, in concentrated aqueous solution, the amounts of the salt of L-ascorbic acid of the formula III and the alkaline earth metal hydroxide used as the base being arranged so that the pH value of the reaction medium is maintained in the range of about 8 to about 11 and a stepped transfer of, in each case, a phosphate group takes place of the polyphosphate of the formula II to the salt of L-ascorbic acid of the formula III until essentially the polyphosphate has been consumed and only 2-monophosphate salt of. L-ascorbic acid of formula I.

In the scope of the above definition it is to be understood under the term "an alkali metal ion" especially a sodium or potassium ion, preferably sodium binding. The alkaline earth metal ion is especially a calcium ion or a magnesium ion, the former being preferred. In this case and taking into consideration its divalence, the alkaline earth metal ion is in each case representing as an ion medium, so that, for example, a calcium ion M + in formula I, II or III is in this sense as 1 / 2 Ca2 +. Although the M + ions in formulas I, III and III may be the same or different, the individual meaning depends on the nature of the salt of L-ascorbic acid of formula III used for the production of the polyphosphate of formula II and the agent phosphorylating as well as the nature of the alkaline base that is used, with which, among others, the exchange of ions also plays a rule. Suitably, the same base used for the production of the polyphosphate is used as the base in the process according to the invention. This can be illustrated on the basis of an example: when the sodium salt of L-ascorbic acid (of formula III where M + means Na +) is used, sodium trimetaphosphate of the formula is used As the phosphorylating agent and calcium hydroxide [Ca (OH) 2] is used as the base (all preferred reagents), formulas I, II and III can be represented, among others and simply, as follows: and respectively From this it will be evident that n is also dependent on the nature of the phosphorylating agent: for example, n means 3 when sodium trimetaphosphate is used as the phosphorylating agent and means 6 when sodium hexametaphosphate is used for this purpose. It should further be borne in mind that the product of the formula I or I 'is inevitably produced as a mixture of different alkali metal and alkaline earth metal salts of L-ascorbic acid 2-monophosphate and can never be represented by a simple formula I. The course of the process according to the invention will be evident from Reaction Scheme 2 which follows, where, for the purpose of a clear and simplified presentation, sodium salt of L-ascorbic acid of the formula III 'is used, it is used sodium trimetaphosphate as the phosphorylating agent (for the production of 2-polyphosphate of L-ascorbic acid of the formula II ') and calcium hydroxide is used as the base; thus, a 2-monophosphate of L-ascorbic acid is prepared, which characterizes, among others, molecules of the formula I ': Reaction Scheme 2 + III "+ 1/2 Ca (OH) 2 - H20 + III '+ 1/2 Ca (OH) 2 - H20 r The production of 2-polyphosphate of L-ascorbic acid of the formula II can be carried out previously (separately) or in situ, preferably in situ. From a 2-polyphosphate of L-ascorbic acid of formula II, produced separately or in situ, the molar ratio of the salt of L-ascorbic acid of formula III to 2-polyphosphate of L-ascorbic acid of the formula II rises, conveniently, to around nl: l, the deviation of this relation not increasing, preferably, to more than around 30%. When it is desired to produce the 2-polyphosphate of L-ascorbic acid of the formula II separately, this may be carried out in a manner known per se, conveniently in accordance with the method described in US patent 5,110,950. The reaction product can be isolated (evaporated) or used immediately as an aqueous solution for the further reaction (with the salt of L-ascorbic acid of formula III). The preferred phosphorylating agent for separate production (and also for in situ production) of L-ascorbic acid 2-polyphosphate is sodium trimetaphosphate, this polyphosphate having three phosphate groups in the molecule (n = 3). In principle, higher metaphosphates can also be used, for example the above-mentioned sodium hexametaphosphate or polyphosphoric acid. With respect to the in situ production of L-ascorbic acid 2-polyphosphate, the phosphorylating agent is added, conveniently, to the concentrated solution of the salt of L-ascorbic acid. The phosphorylating agent, for example sodium trimetaphosphate, can be added, for example, as an aqueous solution or as a solid, with the latter addition method being preferred. Advantageously, the addition of the base, for example calcium hydroxide, is also carried out separately or in a mixture with the phosphorylating agent. The simultaneous addition of the phosphorylating agent and the base is preferred, especially with the addition of a mixture of the two. In the preparation of L-ascorbic acid 2-monophosphate itself the form in which it is added individual reagents is of particular significance. The L-ascorbic acid salt of formula III must always be present in the reaction medium in an excess vis-à-vis L-ascorbic acid 2-polyphosphate. This is obtained, for example, by first preparing an aqueous solution of the L-ascorbic acid salt which is concentrated as much as possible (virtually saturated), conveniently by treating a concentrated aqueous solution of ascorbic acid with alkaline hydroxide, by sodium hydroxide example. Then the addition of 2-polyphosphate of L-ascorbic acid (produced separately) or the phosphorylating agent (for in situ production of this polyphosphate), for example sodium trimetaphosphate, as well as base, for example calcium hydroxide, to the concentrated aqueous solution of the salt of L-ascorbic acid is sprayed throughout the reaction period, so that the 2-polyphosphate of L-ascorbic acid (optionally produced in situ) and the salt of L-ascorbic acid reacts immediately with each other under prevalently alkaline conditions. In this case the pH value must be kept within the range of about 8 to about 11 with the addition of the base. Because the reaction medium must be as concentrated as possible, in the case of the in situ production of L-2-polyphosphate Ascorbic acid the phosphorylating agent and the base are advantageously added as solids. The pH value can be adjusted continuously by appropriate dosing of the base, even when mixed with the phosphorylating agent versus the base. In addition, the rate of addition of the phosphorylating agent and base should be adjusted so that it does not precipitate L-ascorbic acid 2-polyphosphate; the reaction is consequently carried out so that the polyphosphate further reacts as rapidly as possible with the salt of L-ascorbic acid via (in each case) the salt of L-ascorbic acid minus polyphosphate, for example 2- L-ascorbic acid diphosphate, to give the 2-monophosphate of L-ascorbic acid. In practice, for this purpose, the phosphorylating agent is added rather quickly at the beginning and quite slowly towards the end of the reaction. It is also recommended to ensure a good intermixing of the reactants in order that the added solid starting materials are quickly put into intensive contact with the liquid reaction medium. The salt of L-ascorbic acid used in the process according to the invention is preferably an alkali metal salt, especially the sodium salt (III = III '), because these salts are especially soluble in water. The alkali metal salts Ascorbic acid can be obtained, for example, previously, by lactonizing the esters of 2-keto-L-gulonic acid, for example methyl 2-keto-L-gulonate, with solid bicarbonate, sodium carbonate or sodium hydroxide. In each case an aqueous solution of the salt is produced, preferably a solution which is almost saturated at the reaction temperature. In order to adjust the PH value within the range of about 8 to about 11, in the case of in situ production of the 2-polyphosphate of L-ascorbic acid, it is conveniently added about 0.5 to about 0 , 8 mole, preferably about 0.55 to about 0.65 mole, of alkaline earth metal hydroxide per mole of L-ascorbic acid salt. Calcium hydroxide is the preferred alkaline earth metal hydroxide. Because the alkaline earth metal hydroxides are not particularly water-soluble, the alkaline earth metal hydroxide may be added as a suspension in water. However, the alkaline earth metal hydroxide is preferably added as a solid, especially, as indicated above, in a mixture with the phosphorylating agent (in situ production of 2-polyphosphate of L-ascorbic acid). The amount of the phosphorylating agent used is chosen so that the final content of the 2-monophosphate of L-ascorbic acid in the final product is as high as possible, that is, as much L-ascorbic acid salt as possible for consumption. When sodium trimetaphosphate is used, it is obtained satisfactorily when around 0.3 to about 0.5 mol, preferably about 0.35 to about 0.45 mol of phosphorylating agents are used per mole of L-ascorbic acid salt. . The process according to the invention is conveniently carried out at temperatures in the range of about 20 ° C to about 80 ° C, preferably at temperatures in the range of about 40 ° C to about 60 ° C. In general, the temperature rises gradually in the course of the process, for example from about 40 ° C initially to around 60-70 ° C towards the end of the reaction. After completion of the reaction the temperature is advantageously lowered in order to stop the reaction. During the reaction, the pH value is preferably from about 9 to about 10. The reaction is excessively slow at an excessively low pH value. A pH value that is excessively high is also disadvantageous. The pH value should not be substantially higher than 10, in any case higher than around 11, since the salt of L-ascorbic acid has only low stability under strongly alkaline conditions and since the inorganic phosphates are progressively formed. In the case of an excessively high pH value of excessively high pH of L-ascorbic acid 2-polyphosphate and less phosphorylated L-ascorbic acid salt, for example 2-L-ascorbic acid diphosphate, they are converted to 2-monophosphate acid L-ascorbic by dissociation of phosphate groups with the base and not by reaction the salt of L-ascorbic acid; therefore the content of inorganic salts in the final product increases, which is clearly a disadvantage. The reaction time required to obtain a satisfactory yield of L-ascorbic acid 2-monophosphate of formula I depends on several factors, especially the reaction temperature, the pH value, the amount of water in the reaction mixture as well as the agitation intensity. In general it is preferred to add L-ascorbic acid 2-polyphosphate rather slowly or to produce it in situ instead. to add it quickly. When the pH value and the temperature are not unnecessarily high and an excessive amount of oxygen is not present, a somewhat prolonged reaction time is not disadvantageous. Typical reaction times of around 1 to about 4 hours, preferably around 1 1/2 to about 2 1/2 hours. After completion of the reaction the obtained mixture can be cooled, for example to about 30-40 ° C, and diluted with water until the viscosity is suitable for spray drying, for example around 100 mPa, and finally spray dried. When spray drying is carried out, practically no by-products are produced which subsequently have to be discarded. Advantageous in the process according to the invention is the considerable by-product avoidance and the high content (high yield) of desired L-ascorbic acid 2-phosphate of the formula I. In this way the raw material costs and costs of energy in spray drying are reduced to a minimum. The process according to the invention is illustrated by means of the following examples in which, with the exception of example 2, the content of 2-monophosphate of L-ascorbic acid and 2-polyphosphates in each case is given in equivalents of acid L-ascorbic: EXAMPLE 1 Reaction of L-ascorbic acid 2-triphosphate (main constituent of the mixture thus designated) with sodium ascorbate. 67.3 g (340 mmol) of sodium ascorbate are added to 50 ml of water in a double-jacketed reaction vessel and 750 ml while stirring and under a nitrogen atmosphere at 60 ° C and thereby dissolving the Most. The pH value is adjusted to 9.5 with 3.7 g of calcium hydroxide. 2 nr. 87 g of solid L-ascorbic acid 2-triphosphate are added in portions n over the course of 2 hours.

(HPLC analysis: 4.3% ascorbic acid, L-ascorbic acid 0.5% as monophosphate, L-ascorbic acid 1.4% L-ascorbic acid 0.5% as 2-monophosphate, L-ascorbic acid 1.4% as 2-diphosphate, as well as L-ascorbic acid 21.1% as 2-triphosphate), adding 56 g during the first hour and 29 g during the second hour. The pH value is maintained at 9.5 with the addition of 33.9 g of calcium hydroxide. Sufficient water (a total of 50 g) is added so that the suspension can always be stirred well. After the reaction is complete, the batch is evaporated to dryness (water content: 10.5%). HPLC analysis of the dried product indicates 10.9% L-ascorbic acid (residual, not phosphorylated), L-ascorbic acid), 34.5% as 2-monophosphate and L-ascorbic acid 0.6% as 2-diphosphate. The L-ascorbic acid 2-triphosphate can no longer be detected.

EXAMPLE 2 a) Separate production of a solution of L-ascorbic acid 2-polyphosphate 150 ml of water are cooled to 0 ° C in a reaction vessel with double jacket. Then 114.44 g of sodium trimetaphosphate is added while stirring. The pH value is adjusted to 11 with dead lime (a suspension of 205% calcium hydroxide in water, which gives the solution of sodium trimetaphosphate.) 67.32 g of sodium ascorbate are dissolved in 150 ml of water. 11 with dead lime, then the solution is cooled to 0 ° C to give the sodium ascorbate solution, the sodium ascorbate solution is quickly added to the sodium trimetaphosphate solution, the temperature is increased to 30 ° C in the course of 2 hours The pH value is maintained at 11 with dead lime, after 2 hours the batch is cooled to 0 ° C, which provides the solution of 2-polyphosphate of L-ascorbic acid. b) Reaction of L-ascorbic acid 2-polyphosphate with sodium ascorbate. 134.64 q of sodium ascorbate are dissolved in 100 ml of water at 60 ° C while stirring and under a nitrogen atmosphere in a 500 ml double-jacketed reaction vessel. The pH value is adjusted to 10.5 with dead lime. Half of the 2-polyphosphate solution of L-ascorbic acid is added within one hour and the remainder is added within two hours. The pH value is maintained at 10.5 with dead lime. During the last two hours water is distilled off under reduced pressure. After the reaction is complete, the bath is neutralized to pH 7 with sulfuric acid and diluted with 300 ml of water. The HPLC analysis indicates the following distribution of L-ascorbic acid: 14,; 3% unphosphorylated, 76.2% as monophosphate, 7.6% as diphosphate, < 1% as the triphosphate and < 2% as additional L-ascorbic acid 2-polyphosphates.

EXAMPLE 3 In situ production of L-ascorbic acid 2-polyphosphate and its reaction with sodium ascorbate. 100 g of water are placed in a double jacket reaction vessel. Then it is degassed by applying vacuum. The vacuum is quenched with nitrogen and 176 g (1 ml) of ascorbic acid are added. The ascorbic acid is neutralized with 141.6 g of 28% sodium hydroxide solution while stirring and under reduced pressure. The vacuum is interrupted with nitrogen and the temperature is adjusted to 50 ° C. Within 2 hours a mixture of 142.8 g (0.467 mol) of sodium trimetaphosphate and 51.9 g (0.7 mol) of calcium hydroxide is added under nitrogen. Addition is rapid at the beginning of the reaction and slows down towards the end of the reaction. The reaction mixture is stirred for 60 minutes, neutralized with 5.2 g of 98% sulfuric acid and diluted with 300 g of water. An aliquot (about 10 ml) is removed from the reaction mixture and evaporated to dryness under reduced pressure. The HPLC analysis indicates L-ascorbic acid 1.3% L-ascorbic acid 34.3% as the 2-monophosphate and L-ascorbic acid 3.5% as the 2-disphosphate, a total of 42% phosphorylated ascorbic acid .

EXAMPLES 4-7 These examples were carried out analogously to Example 3, under but under reaction conditions variables In particular, the amount of sodium trimetaphosphate was gradually reduced. The results obtained are shown in the following table. Table E j us 4 5 6 7 Water (g) 50 50 50 50 ASC (g) 176 176 176 176 NaOH 28% (g) 163.5 166 163.5 163.5 STMP (g) 132.6 112.2 102 91.8 Ca (OH) 2 (g) 37 37 37 33.3 H2S04 (g) 4 8.8 10.4 8.9 Water (g) 200 200 200 200 reaction solution (g) 763.1 750 738.9 723.5 Temperature (° C) 40-60 40 40-60 40-60 pH value of NaASC solution 9.9 10 10 10 STMP / Ca (OH) addition in 2 h 4 h 2 h 2 h second agitation 0.25 h l h 0.25 h 0.25 h HPLC analysis (ASC equivalents): non-phosphorylated ASC (%) 5 7.1 8.7 11.4 ASC as monophosphate (%) 31.6 37.9 39.4 38.1 ASC as diphosphate (%) 6.2 2.5 1.2 0.9 Total ASC phosphates (%) 39.3 41.5 41.6 39.6 Total ASC (%) 44.3 48.6 50.3 51 ASC = L-ascorbic acid STMP = Sodium trimetaphosphate NaASC = Sodium ascorbate EXAMPLE 8 Drying in a fluidized bed of the product 165 g of water are placed in a 750 ml double-jacketed reaction vessel. The vacuum is interrupted with nitrogen and 176 g (1 mol) of ascorbic acid are added. While stirring, 88.4 g of 50% sodium hydroxide solution are added. Then the pH value is from 9.1. The temperature is adjusted up to 40 ° C. A mixture of 132.6 g (0.433 mol) of sodium trimetaphosphate and 44.45 g (0.6 mol) of calcium hydroxide is added evenly within two hours, under nitrogen, and the temperature in the reactor is increased to 60 °. C. The mixture is stirred for 30 minutes, cooled to 40 ° C and diluted with 200 g of water. The reaction mixture is then evaporated under reduced pressure. The resulting solid product is ground and dried in a fluidized bed dryer with 10 mJ hot air at 100 ° C for 30 minutes. 364 g of beige brown powder with 6.3% residual moisture are obtained. HPLC analysis indicates 3% L-ascorbic acid, 33.2% L-ascorbic acid such as 2-monophosphate and 3.8% L-ascorbic acid such as 2-diphosphate, a total of 37.6% ascorbic acid phosphorylated EXAMPLE 9 Spray drying of the product 100 g of water are obtained in a double jacket reaction vessel. Then it is degassed by applying vacuum. The vacuum is interrupted with nitrogen and 176 g (1 mol) of ascorbic acid is added. Ascorbic acid is neutralized with 142.8 g of hydroxide solution sodium at 28% while stirring and under reduced pressure. The pH value is adjusted to 10 with the addition of 18.6 g of calcium hydroxide. The vacuum is interrupted with nitrogen and the temperature is adjusted to 40 ° C. A mixture of 132.6 g (0.433 mol) of sodium trimetaphosphate and 48.2 g (0.65 mol) of calcium hydroxide is added within 4 hours, nitrogen. The reaction mixture is stirred for 90 minutes, neutralized with 7.1 g of 98% sulfuric acid and diluted with 300 g of water. It is dried by laboratory spray. According to the HPLC analysis, the powder contains 3.7% L-ascorbic acid, 38% L-ascorbic acid such as 2-mono-phosphate, and 2.8% L-ascorbic acid such as 2-diphosphate. , a total of 46.9% phosphorylated ascorbic acid.

EXAMPLE 10 Use of sodium ascorbate from the lactonization of 2-methyl keto-L-gulonate 208.4 g of methyl 2-keto-L-gulonate are dissolved in 500 g of methanol and the solution is heated to boiling while stirring. 52 g of sodium carbonate is added in the course of 2 hours. Then the pH value is 8. The mixture is stirred for 30 minutes, cooled to 40 ° C and The precipitated sodium ascorbate is filtered off and washed with 100 g of methanol. Dry the wet sodium ascorbate in a drying oven at 40 ° C under reduced pressure. About 198.1 g of crude sodium ascorbate with a pure sodium ascorbate content of about 94% are obtained. 198.1 g of crude sodium ascorbate are dissolved in 230 g of water at 40 ° C in a 500 ml double-jacketed reaction vessel. The temperature is increased to 60 ° C within 2 hours and a mixture of 132.6 g (0.433 mol) of sodium trimetaphosphate and 44.45 g (0.6 mol) of calcium hydroxide is added. The mixture is stirred for 30 minutes, cooled to 40 ° C and diluted with 200 g of water. The entire reaction mixture is evaporated as rapidly as possible on a rotary evaporator under reduced pressure at a bath temperature of 60 ° C under reduced pressure (yield by weight: 375.8 g). The water content is 6, 7%. According to the HPLC analysis the powder contains 3.7% L-ascorbic acid such as 2-monophosphate, 36% L-ascorbic acid such as 2-diphosphate as well as 1.95 L-ascorbic acid as the 2 -triphosphate.

EXAMPLE 11 Use of sodium ascorbate from lactonization of methyl 2-keto-L-gulonate without isolation of sodium ascorbate. 208.4 g of methyl 2-keto-L-gulonate are dissolved in 500 g of methanol and the solution is heated to boiling with stirring. 52 g of sodium carbonate are added over the course of 2 hours, during which the pH value does not rise substantially above 8. The mixture is stirred for a further 30 minutes, diluted with 230 g of water and the mixture is distilled off. most of the methanol on a Vigreux column. The distillation residue (439 g) is cooled to 40 ° C. then the temperature is increased from 40 ° C to 60 ° C over the course of 2 hours under nitrogen and a mixture of 132.6 g of sodium trimetaphosphate and 44.45 g of calcium hydroxide is added. The mixture is stirred for a further 30 minutes. The reaction mixture is evaporated as rapidly as possible under reduced pressure at a bath temperature of 60 ° C and the residue is ground in a mortar and then dried in a drying oven at 60 ° C under reduced pressure (yield in weight: 388 g). The water content is 9%. In accordance with the HPLC analysis the powder contains 3.6% L-acid ascorbic, 30.2% L-ascorbic acid such as 2-monophosphate, 4.9% L-ascorbic acid such as 2-diphosphate, as well as 0.9% L-ascorbic acid such as 2-triphosphate.

EXAMPLE 12 Use of potassium hydroxide as the base 175.6 g of water are placed in a double jacket reaction vessel and 750 ml and degassed by the application of vacuum. The vacuum is interrupted with nitrogen and 176 g (1 mol) of ascorbic acid are added. The ascorbic acid is neutralized with 113.2 g of 55.9% potassium hydroxide solution while stirring and under reduced pressure. The vacuum is interrupted with nitrogen and the temperature is adjusted to 40 ° C. The temperature is increased from 40 ° C to 60 ° C within 2 hours under a nitrogen atmosphere and a mixture of 132.6 g (0.433 mol) of sodium trimetaphosphate and 48.2 g (0.65 mol) of calcium hydroxide. The mixture is stirred for a further 15 minutes and diluted with 200 g of water. The reaction mixture is evaporated as rapidly as possible under reduced pressure at a bath temperature of 60 ° C, and the residue is ground in a mortar and then dried in a drying oven at 60 ° C under reduced pressure (yield in weight: 391.7 g).

The water content is 55. According to the HPLC analysis, the powder contains 4.7% L-ascorbic acid, 32.5% L-ascorbic acid such as 2-monophosphate, 3.95 L-acid. ascorbic as 2-diphosphate, as 1.1% of L-ascorbic acid as 2-triphosphate.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, property is claimed as contained in the following:

Claims (10)

CLAIMS 1.- A process for the preparation of alkali metal and alkaline earth metal salts of L-ascorbic acid 2-monophosphate of the formula wherein each M + means an alkali metal ion or the equivalent of an alkaline earth metal ion, which process is characterized in that it comprises reacting a 2-polyphosphate of L-ascorbic acid of the general formula where M + has the meaning indicated above and n means an integer of 2, under alkaline conditions with an alkali metal or alkaline earth metal salt of L-ascorbic acid of the general formula wherein M + has the meaning indicated above, in concentrated aqueous solution, the amounts of the salt of L-ascorbic acid of formula III and alkaline earth metal hydroxide as the base being arranged so that the pH value of the reaction medium is maintained in the range, from about 8 to about 11 and a stepped transfer of, in each case, a phosphate group O taking place.
1. II -p-o- ot of the polyphosphate of the formula II to the salt of L-ascorbic acid of the formula III until essentially the polyphosphate is consumed and only 2-monophosphate salt of L-ascorbic acid is present.
2. 2. - A method according to claim 1, characterized in that the 2-polyphosphate of L-ascorbic acid of formula II is produced in situ.
3. 3, - A method, according to claim 1 or 2, characterized in that the 2-polyphosphate of L-ascorbic acid used has the formula The alkali metal salt of L-ascorbic acid used has the formula and calcium hydroxide is used as the base.
4. 4. - A method, according to any of claims 1 to 3, characterized in that the 2- L-ascorbic acid polyphosphate of formula II or II 'is produced separately or produced in situ using sodium trimetaphosphate as the phosphorylating agent.
5. 5. - A process according to any of claims 1 to 4, characterized in that the 2-polyphosphate of L-ascorbic acid of formula II is produced in situ and for this purpose a mixture of sodium trimetaphosphate is added as the phosphorylating agent with the base, preferably calcium hydroxide.
6. 6. - A process, according to any of claims 1 to 5, characterized in that the 2-polyphosphate of L-ascorbic acid of formula II is produced in situ and about 0.5 to about 0.8 mol, of preferably about 0.55 to 0.65 mol, of alkaline earth metal hydroxide per mole of L-ascorbic acid salt of formula III.
7. 7. - A method, according to any of claims 1 to 6, characterized in that the 2-polyphosphate of L-ascorbic acid of formula II is produced in situ and used around 0.3 to about 0.5 mol, preferably around 0.35 to around 0.45 mol, of sodium trimetaphosphate as the phosphorylating agent per mole of L-ascorbic acid salt of formula III.
8. 8. - A method according to any of claims 1 to 7, characterized in that the reaction is carried out at temperatures in the range of about 20 ° C to about 80 ° C, preferably in the range of about 40 ° C to around 60 ° C.
9. 9. - A method, according to any of claims 1 to 8, characterized in that the pH value is from about 9 to about 10.
10. 10. - A process according to any of claims 1 to 9, characterized in that after completing the reaction, cooling and dilution to an appropriate viscosity, for spray drying, the obtained mixture is spray dried. SUMMARY OF THE INVENTION A process for the preparation of alkali metal and alkaline earth metal salts of L-ascorbic acid 2-monophosphate comprises reacting a 2-polyphosphate of L-ascorbic acid under alkaline conditions with an alkali metal or alkaline earth metal salt. of L-ascorbic acid in concentrated aqueous solution, the amounts of the L-ascorbic acid salt and the alkaline earth metal hydroxide used as the base being arranged, so that the pH value of the reaction medium is maintained in the range of about 8 to about 11 and a stepped transfer of, in each case, a phosphate group of the polyphosphate to the salt of L-ascorbic acid until essentially the polyphosphate is consumed and only 2-monophosphate of L-ascorbic acid is present. Preferably, the 2-polyphosphate of L-ascorbic acid is produced in situ and calcium hydroxide is used as the base. Independently that if L-ascorbic acid 2-polyphosphate is produced separately or in situ, sodium trimetaphosphate is preferably used as the phosphorylating agent. Another aspect of the present invention comprises spray drying the mixture obtained after completion of the reaction, cooling and dilution to an appropriate viscosity. The product of the process according to the invention is suitable as an additive for human and animal foods; it is especially stable against oxidative and thermal degradation and has an especially high content of L-ascorbic acid bis-a-bis-polyphosphate monophosphate, and is therefore mainly used, preferably, for nutritive enrichment of fish feed.