TECHNICAL FIELD;

This invention relates to a method for synthesis of beta glycerophosphate disodium salt involving the recovery and reuse of tiglic acid a key reagent/ raw material.

BACKGROUND:

The glycerophosphates are important chemical compounds, which assist in a variety of biological and pharmaceutical activities. They are commonly used in formulations, mineral fortification, toothpaste, sports beverages etc. Such broad uses make glycerophosphates valuable raw materials for pharmaceutical consumption.

Previous methods known in the art or as described in publication Tetrahedron, 1988, 44, 6373 or WO2010/80969 Al, 2010 for the synthesis of beta glycerophosphates, can yield the required product. However, the synthesis always results in the formation of mixture of compounds or related impurities that need further purification, which would lower the overall efficiency and increase the associated costs incurred for the production of the beta glycerophosphates. Such existing technologies need to be further investigated in order to devise and develop a process that can allow for the isolation of the required product easily and in high purity. If such a process can also allow the recovery and reuse of raw materials, it would have added commercial and environmental value.

Further the existing processes involve tedious and expensive purification techniques such as distillations or chromatography due to interference of starting material or protecting group or impurities.

To overcome such technical difficulties that affect the overall yield and cost of the widely useful bioactive compounds i.e. beta-glycerophosphate metal salt, subsequently wastage of the raw materials, the present inventors have developed improved method, for the production of beta glycerophosphate (compound 8) without having to rely on any tedious and expensive purification techniques such as distillations or chromatography wherein, the desired product is achieved primarily due to the properties and structural features of the tigloyl group that allows for the selective esterification of the 1,3 hydroxyl
functionality (major product) of the starting material glycerol whilst relying on simple solvent washing techniques to provide the final compound 8 in high purity and allowing for the efficient recovery of raw material i.e. tiglic acid to enable reuse.

SUMMARY OF THE INVENTION:
The present invention provides for the method of synthesis of beta glycerophosphates disodium salt with high purity and yield involving tiglic acid, a key raw material in the synthesis. The method of the instant invention allows for the recovery and reuse of tiglic acid.

In an aspect the invention provides a method for synthesis of beta glycerophosphates disodium salt with high purity and yield, characterized by the use of tiglic acid a key raw material comprising;

a) treating tyglic acid (1) with thionyl chloride to obtain tigloyl chloride (2) under neat condition;

b) reacting tigloyl chloride (2) with glycerol (3) in presence of a base at a temperature of -5 to 0°C
and solvent to obtain 1, 3 tigloyl ester of glycerol (4);

c) phosphorylating 1, 3 tigloyl ester of glycerol (4) in presence of phosphorylating agent in a solvent to obtain Phosphorylated 1, 3 tigloyl ester of glycerol (5) with simultaneous removal of triester from reaction mass;

d) hydrolyzing the Phosphorylated 1, 3 tigloyl ester of glycerol (5) to obtain 1, 3 tigloyl ester of beta glycerophosphate (6);

e) converting 1, 3 tigloyl ester of beta glycerophosphate (6) into 1, 3 tigloyl ester of beta glycerophosphate disodium salt (7) by treating with aqueous sodium hydroxide;

f) de-esterifying the 1, 3 tigloyl ester of beta glycerophosphate disodium salt (7) into desired beta glycerophosphate disodium salt (8) in presence of a base and methanol; and

g) recovering the tiglic acid (1) from mother liquor.

In another aspect the present invention provides recovery of key raw material i.e. tiglic acid from the mother liquor containing wasteful material.

DETAILED DESCRIPTION OF THE INVENTION:

The invention will now be described in detail in connection with certain preferred and optional embodiments, so that various aspects thereof may be more fully understood and appreciated.

The present invention describes an efficient synthesis of beta glycerophosphate. The method allows for the isolation of beta glycerophosphate without any chromatography at any step and only relying on extractions and washing with suitable solvents to remove impurities and related substances.

Accordingly, in preferred embodiment the invention provides a method for synthesis of beta glycerophosphates disodium salt with high purity and yield characterized by the use of tiglic acid a key raw material comprising;

a) treating tiglic acid (1) with thionyl chloride to obtain tigloyl chloride (2) under neat condition;

b) reacting tigloyl chloride(2) with glycerol (3) in presence of a base at a temperature of -5 to 0°C and solvent to obtain 1, 3 tigloyl ester of glycerol
(4);

c) phosphorylating 1, 3 tigloyl ester of glycerol (4) in presence of phosphorylating agent in a solvent to obtain Phosphorylated 1, 3 tigloyl ester of glycerol (5) with simultaneous removal of triester from reaction mass;

d) hydrolyzing the Phosphorylated 1, 3 tigloyl ester of glycerol (5) to obtain 1, 3 tigloyl ester of beta glycerophosphate (6);

e) converting 1, 3 tigloyl ester of beta glycerophosphate^) into 1, 3 tigloyl ester of beta glycerophosphate disodium salt (7) by treating with aqueous sodium hydroxide;

f) de-esterifying the 1, 3 tigloyl ester of beta glycerophosphate disodium salt (7) into desired beta glycerophosphate disodium salt (8) in presence of a base and methanol; and

g) recovering the tiglic acid (1) from mother liquor.

In another embodiment, the instant invention provides stepwise reaction methodology for the synthesis of beta glycerophosphate of compound (8) as graphically illustrated in scheme 1. The method covers the synthesis of (tigloyl) chloride (2) from tiglic acid (1); esterifying 1, 3 hydroxyl groups of glycerol (3) to form compound (4). Treating compound (4) with a phosphorylating agent to yield compound 5 ('Y' is halogen), which on hydrolysis in presence of an aqueous solution or water to form compound (6), under conditions that allow for the formation of a salt as depicted in compound (7) and finally de-esterification to give a compound comprising of formula (8).
The synthetic route for the preparation of beta glycerophosphate disodium salt involving tiglic acid is described in below scheme 1. Scheme 1:

Lg is a leaving group or an activating group that facilitates esterification

Y is a halogen,

M is selected from Group 1A metal ions,

Z is any group that can form a bond with an activated tigloyl moiety.

Accordingly, the 1,3-hydroxy groups were esterified with tigloyl chloride to give di (1.3 positions) and tri (1.2.3 positions) esterified compounds in presence of base. The di and tri esterified compounds were isolated, the progress of the reaction monitored by thin layer chromatography, confirmed by *H NMR and HPLC. The 1,3-diesterified compound 4 was phosphorylated in presence of base to give compound 5.

The compound 5 on aqueous hydrolysis gives compound 6, which further reacted with inorganic base results salt formation compound 7. The compound 7 was de-esterified under basic media to give beta-glycerophosphate (compound 8). The step wise reactions are discussed below.

a. Synthesis of tigloyl derivative (2):
Compound (2) was derived from tiglic acid (1) by the known derivatization process which includes halogenation, acylation, esterification, preferably halogenation in presence of chlorinating agent under neat condition to obtain (tigloyl derivative) (2) with good yield and purity.

According to the scheme 1 chlorination was accomplished with thionyl chloride, where tiglic acid (1) converted into tigloyl chloride (2) under neat condition. The mole to mole ratio will vary on different conditions; the most preferred embodiment's mole to mole ratio of tiglic acid (1) to tigloyl chloride compound (2) may range from 1.0 to 2.0, preferably 1.1 to 1.5.

b. Synthesis of 1,3-diesterified glycerol (4):
Compound 4 was obtained from glycerol 3 using tigloyl chloride 'Tg', which is depicted in Scheme 1. The reaction allows for the selective esterification of the hydroxyl groups in the one and three positions of compound. The mole to mole ration will vary compound 3 with tigloyl chloride; the preferred mole to mole ratio of compound 3 convert to compound 4 may range from 2.0 to 2.1. In general the reaction temperature is maintained in the range of-5 to 25 °C. The said transformation can be conducted in any suitable organic solvent, preferably methyl tertiary butyl ether (MTBE). The reaction can be performed using any suitable organic and inorganic base, preferably an organic base such as pyridine or triethyl amine. The excess organic base and tigloyl chloride may be quenched with water, bicarbonate solution.
The most preferred reaction temperature was -5 to 0 °C, temperature should not exceeds to 0 °C to prevent isomerisation, which can leads alpha isomer. The crude compound 1,3-diesterified glycerol, particularly 1,3 tigloyl ester of glycerol (4) was isolated and confirmed with *H NMR and HPLC.

c. Conversion of compound (4) to compound (5):
The invention describes synthesis of compound 5 was achieved from corresponding compound 4 using phosphorylating agent, which is depicted in scheme 1. 1,3-diesterified glycerol (4) was reacted with phosphorylating agent, in presence of bases (organic, inorganic), but the preferred organic base is triethyl amine. The reaction was agitated at temperature in range of 10 to 25 °C. to form corresponding compound 5, wherein, Y is the halogen. The mole to mole ratio will vary on different conditions but the preferred mole to mole ratio of compound 4 convert to compound 5 may range from 1.2to 1.5. The reaction was conducted in temperature range of-5 to 25 °C and in organic solvent such as methyl tertiary butyl ether (MTBE).

d. Conversion of compound (5) to compound (6):
Compound 6 was synthesised from corresponding compound 5 by hydrolysis in presence of water, which is depicted in scheme 1. The compound 5 was reacted with water to form corresponding compound 6. The inorganic salts may be quenched with cold water many times, the preferred washings are three times, and the reaction preferred temperature was in the range of 10° to 30 °C. The temperature should not exceed above 30 °C to prevent impurities, preferably in the range of 10° to 25 °C.

e. Conversion of compound (6) to compound (7):
Compound 7 was synthesised from corresponding compound 6 using base, which is depicted in scheme 1. As described the compound 6 was reacted with base having one metal ion (M) to form compound 7. The metal ion preferably selected from Group 1 metal ions such as Lithium, Sodium, and Potassium.

Although, the pH of the reaction mass may be variable but preferred pH range is between 12 to 13. The concentration of the base may be varied depending on reaction conditions but preferred embodiments comprise 50% aqueous solution (w/v) the base is selected from the group NaOH, KOH, LiOH, NaHC03, NaC03, preferably NaOH. The reaction was conducted in temperature range of 10 to 20 °C and in presence of organic solvent, preferably methanol.

f. Conversion of compound (7) to compound (8):
Beta glycerophosphate disodium salt i.e. compound 8 was synthesised from corresponding compound 7 by de-esterifying the same using aqueous inorganic basic solution, which is depicted in scheme 1. The compound 7 was de-esterified via hydrolysis to give corresponding compound 8. The de-esterification can be achieved using inorganic bases and organic bases but the preferred hydrolysis reagents were sodium hydroxide, potassium hydroxide and lithium hydroxide. The pH of the reaction was different with different reaction condition but here preferred embodiments in the range of 12-14. The pH was adjusted using pH meter. The reaction was conducted at a temperature range of 10 to 65 °C in presence of methanol. After adjusting pH, the reaction was heated to reflux in temperature range of 65 to 75 °C. The time taken for completion of the reaction varies, the preferred time in the range between lh to 2h. The impurities were removed with simple washing using suitable solvent.

After completion of the reaction, the reaction mass was cooled to 0 °C, filtered the precipitated product, the crude product was suspended in water: methanol (5% water), and filtered, washed with methanol and dried under vacuum to give pure beta glycerophosphate in an yield of 45% with purity more than 99.99%.
The compound 4, without isolation, proceeded to phosphorylation in presence of base. The mole ratio may be varied but preferred mole ratio of the compound 4 to base in range of 1.3 to 1.5. The reaction preferred temperature ranges between -5 to 25 °C. After completion of the reaction, the tri-ester compound was removed upto maximum level by treating with heptane and toluene mixture (%5 toluene, v/v). The crude compound was taken forward to next step without further purification.

The di-esterified compound 5 was converted to compound 6 using water. The compound 6 was reacted with inorganic base results simultaneously salt formation and de-esterification to give beta glycerophosphate (8). In step wise reaction methodology, it is very difficult to recover all the amount of the starting materials.

However, the instant invention may also perform in-situ, without isolating the reaction intermediates to recover the starting material, tiglic acid in good yield. Accordingly, in another embodiment, the invention provides a synthesis of beta glycerophosphate from glycerol without isolation of intermediates.
Thus the present invention provides synthesis of beta glycerophosphate disodium salt hydrate 8 using tigloyl chloride 2 and glycerol 3 as the starting materials, which is shown in scheme 1.

In another embodiment, the invention provides recovery of key raw material i.e. tiglic acid which can be reused for the selective esterification of 1,3 dihydroxy compounds.

The recovery comprises the evaporation of product free mother liquor containing aqueous methanol under reduced pressure followed by extraction in presence of suitable organic solvent such as ethyl acetate to remove the organic impurities. Further the aqueous layer was cooled to temperature in the range of -5°C to 0°C and neutralised with cone, inorganic acid such as hydrochloric acid to acidic pH in the range of 2 to 4, to get solid precipitate of tiglic acid, the pure recovered tiglic acid is reused for selective esterification of glycerol.

The following examples, which include preferred embodiments, will serve to illustrate the practice of this invention, it being understood that the particulars shown are by way of example and for purpose of illustrative discussion of preferred embodiments of the invention.

EXAMPLES:
Example 1:
Synthesis of (E)-2-methylbut-2-enoyl chloride (tigloyl chloride from tiglic acid) Tiglic acid (300g, leq.) (1) was taken in thionyl chloride (713.8g, 2eq.) containing 2 L three neck round bottom flack were heated to reflux for 2h, until no evolution of hydrogen chloride. The completion of the reaction was monitored by TLC. The excess of thionyl chloride was distilled at atmospheric pressure. The tigloyl chloride (2) was
collected at 140 °C.

(320g, 90%).
'HNMR (CDC13) 5: 7.26-7.31 (q, 2H, 2 olefin-CH), 1.90 (s, 12H, 4CH3)

Example 2:
Synthesis of 1,3-tigloyl ester of glycerol using tigloyl chloride
Charged 100 g of glycerol (1.0 eq) (3) in to a clean dried 3L 3N RBF equipped with mechanical stirrer to that added 1.2 L MTBE, followed by pyridine 180.39 g (2.1 eq) were added at room temperature. After 15 minutes the reaction mass cooled to -5 to 0 °C.

Tigloyl chloride 256.7 g (2.0 eq) was added drop wise over period of 2h, the temperature rages -2 to 2 °C. After completion of addition, the reaction mass stirred at 0 °C for 90 minute and allowed warm to room temperature for 90 minutes. The progress of the reaction was monitored by using TLC and HPLC. The reaction mass diluted with MTBE and water, stirred 15 minutes separated organic layer. The organic layer was washed with 2N HC1, followed by water wash, finally with saturated sodium bicarbonate solution, water wash, and the organic layer separated dried with sodium sulphate and evaporated under reduced pressure.

'H NMR (CDC13) 8: 6.93-6.86 (q, 2H, olefin-CH), 4.12-4.20 (m, 1H) 4.25-4.35 (m, 4H), 1.80 (s, 12H,4CH3)

Example 3:
Synthesis of phosphorylated 1,3 tigloyl ester of glycerol
Charged 240 g (1.0 eq) of 1,3 tigloyl ester glycerol (4) in to a clean dried 3L, 3N, RBF equipped with mechanical stirrer to that added 2.16 L MTBE, followed by triethyl amine 142.13 g (1.5 eq) were added at room temperature. After 15 minutes the reaction mass cooled to -5 to 0 °C. Phosphorous oxy chloride 215.6 g (1.5 eq) was added drop wise over period of 1.5 h, the temperature ranges from -2 to 2 °C. After completion of addition the reaction mass stirred at 0 °C for 2h and allowed warm to room temperature, stirred for 12h. The progress of the reaction was monitored by using TLC and HPLC. The reaction mass diluted with ethyl acetate and cold water, stirred 15 minutes and separated organic layer. The organic layer was washed with cold water, finally the organic layer separated dried with sodium sulphate and evaporated under reduced pressure. 'H NMR (CDC13) 5: 6.7-6.8 (m, 2H, olefin-CH), 4.5-4.6 (m, 1H) 4.25 (d, 4H, J= 4.65 Hz), 1.8 (s, 12H,4CH3)

Example 4:
Synthesis of beta glycerophosphate
Charged 260 g of phosphorylated 1,3 tigloyl ester of glycerol in to a clean dried 3L, 3N, RBF equipped with mechanical stirrer to that added 1.3 L of 5% water: methanol was added at room temperature. After 15 minutes the reaction mass cooled to 0 °C. The pH was adjusted to 12 to 14 using 50% sodium hydroxide aqueous solution, the temperature range between 10 to 20 °C. After that the reaction mass heated to 65 °C for 2 h. The progress of the reaction was monitored by TLC, cooled to 0 °C, solid precipitated was filtered. The crude mass was suspended in 5% water: methanol, stirred 30 minutes filtered and washed with methanol and dried.

(101.59% assay, melting range- 98.8-101.2 °C and 50% yield)
'H NMR 300 MHZ (D20) 5: 3.56 (d, 4H, J= 4.71 Hz), 4.022-4.034 (m, 1H)
13C NMR 300 MHZ (D20) 8: 62.34 (2C), 74.82 (1C)

Example 5:
Recovery of tiglic acid from mother liquor
The mother liquor containing aqueous methanol was evaporated under reduced pressure, the obtained solid was dissolved with water. The aqueous layer was extracted with ethyl acetate to remove any organic impurities. The aqueous layer was cooled to 0 °C and neutralised with concentrated hydrochloric acid to pH = 3, solid precipitated, filtered, dried under vacuum. The recovered tiglic acid is reused for the selective esterification of glycerol.

The tiglic acid recovered from the mother liquor is obtained in 65% yield and >95% purity.

WE CLAIM,

1. A method for synthesis of beta glycerophosphates disodium salt with 101.59% assay, with a melting range of 98.8-101.2 °C from glycerol, characterized by the use of tiglic acid a key raw material comprising:

a) treating tiglic acid with thionyl chloride to obtain tigloyl chloride under neat condition;

b) reacting tigloyl chloride with glycerol in presence of a base at a temperature of -5 to 0°C and solvent to obtain 1,3 tigloyl ester of glycerol;

c) phosphorylating 1,3 tigloyl ester of glycerol in presence of phosphorylating agent in a solvent to obtain Phosphorylated 1,3 tigloyl ester of glycerol;

d) hydrolyzing the Phosphorylated 1, 3 tigloyl ester of glycerol to obtain 1, 3 tigloyl ester of beta glycerophosphate;

e) converting 1,3 tigloyl ester of beta glycerophosphate into 1, 3 tigloyl ester of beta glycerophosphate disodium salt by treating with aqueous sodium hydroxide;

f) deesterifying the 1,3 tigloyl ester of beta glycerophosphate disodium salt into beta glycerophosphate disodium salt in presence of a base and methanol; and

g) recovering the tiglic acid from mother liquor..

2. The method according to claim 1, wherein the base used in step (b) is an organic base selected from pyridine or triethyl amine.

3. The method according to claim 1, wherein the solvent used in step (b) and (c) is methyl tertiary butyl ether.

4. The method according to claim 1, wherein the concentration of aqueous sodium hydroxide is 50%w/v.

5. The method according to claim 1, wherein the base used for de-esterification is an organic base or an inorganic base selected from the group consisting of sodium hydroxide, potassium hydroxide and lithium hydroxide.

6. The method according to claim 1, wherein the phosphorylating agent is phosphorous oxychloride.

7. The method according to claim 1, wherein the beta glycerophosphates disodium salt is obtained in yield 45%.

8. The method according to claim 1, wherein the recovery of tiglic acid from mother liquor comprising;

a) evaporating methanol followed by dissolving the solid obtained in water;

b) extracting aqueous layer to remove organic impurities followed by cooling the aqueous layer and adjusted the pH with concentrated hydrochloric acid up to pH 3 to precipitate the tiglic acid.

9. The method according to claim 8, wherein the tiglic acid is recovered in yield 65% with purity 95%.