DESC:PHARMACEUTICAL PREPARATION OF PENTOSAN POLYSULFATE SODIUM
FIELD OF THE INVENTION
The present application relates to improved processes for the preparation of Pentosan Polysulfate Sodium (PPS) of Formula (I). The application further relates to isolation of its starting material Xylan of Formula (III) having desired characteristics and its use in the synthesis of Pentosan Polysulfate Sodium (PPS).

BACKGROUND OF THE INVENTION
Pentosan polysulfate has been used in pharmaceutical formulations to treat osteoarthritis, as an anticoagulant or for other conditions such as interstitial cystitis, transmissible spongiform encephalopathy (TSE) and immunodeficiency virus (such as HIV/AIDS or Feline Immunodeficiency Virus (FIV)) in mammals, such as humans, food-producing and companion animals (such as feline, canine and equine). Pentosan polysulfate may also be used to treat haematomas, haemorrhoids, frostbite, burns, and multiparameter illnesses such as thrombosis and atherosclerosis.
Several pharmaceutical products contain pentosan polysulfate or a salt thereof as an active ingredient. As an example, Elmiron®, pentosan polysulfate sodium (PPS) having a high sulfation degree and a molecular weight of 4000-6000 Dalton, is authorized in USA for the treatment of Interstitial Cystitis.
Sulfate esters, including heparin, dextran sulfate and PPS are semisynthetic. Their derivation and synthesis have long proved to be very challenging, with production outcomes being highly variable.
Pentosan polysulfate as free acid or in the salt form (typically with inorganic cations such as sodium) is described in the prior art as a mixture of semi-synthetic polysulfated oligosaccharides, generally obtained from Beechwood xylan. Pentosan polysulfate consists of sulfated linear 1-4 conjugated beta-D-xylopyranose units and has 4-O-methyl-D-glucuronic acid randomly attached on every eight to ten xylose units (on average). From a structural point of view, pentosan polysulfate is described as a complex mixture of sulfated polysaccharidic chains having sulfated ?-(1?4)-D-xylopyranose (hereinafter, xylose unit) as the most recurrent repetitive unit. The typical number of xylose units in a PPS mixture reported in the prior art has been between six and thirty. PPS mixtures currently present on the market (when in the form of sodium salt at all SO3 - groups) typically contain 15 to 17% sulfation.
As PPS is derived from natural sources such as Beech wood xylan. In its natural form, PPS consists of molecular chains of varying lengths, or molecular weights. Being obtained from xylan extracted by high trees such as beech, ramifications of 4-O-methyl-glucuronic acid are present and distributed in a not necessarily regular manner.
However, like heparin, the effects of unfractionated natural PPS can be difficult to predict. Therefore, differences in the manufacturing and isolation process (especially during hydrolysis and delignification) lead to different types of Xylan being produced and which can eventually have an impact on the quality of PPS. In practice, it has been difficult to achieve consistency of the heterogeneous mixture of carbohydrates that make up PPS during commercial production.
Pentosan polysulfate is disclosed in US2689848. Said patent discloses a process for producing pentosan polysulfate comprising treating xylan with chlorosulfonic acid in the presence of pyridine to obtain sulfuric acid ester salt of xylan, followed by oxidative depolymerisation in acidic or neutral aqueous medium to obtain a depolymerised product, which is dialyzed and fractionated to obtain the desired product. However, said process does not provide an end product with desired molecular weight profile. Moreover, said process is tedious, costly and provides pentosan polysulfate in low yield. WO2008107906 discloses a process for similarly producing sodium pentosan polysulfate, which involves the use of a nanofiltration membrane system for purification of crude depolymerised pentosan polysulfate. Further, patents like US4713373, US9120877 reported methods for preparation of xylan sulfates having higher degree of sulfation.
Identification of structural signature of PPS samples in Elmiron® and processes for the extraction/preparation of the Xylan are described in Patent Application Publications viz., WO2014114723A1, WO2016184887A1.
Differences in the manufacturing process can result in molecular differences of pentosan polysulfate, such as branching, degree of sulfation, position of the sulfate groups on the polysaccharidic chain and average molecular weight. It is well known that the clinical efficacy of sulfated carbohydrates can be affected by the type and position of SO3 - groups, hence the need to fully control and characterise molecules.
While use of PPS became widespread, and to reduce batch to batch variations that could affect pharmaceutical effectiveness, the fundamental problem to overcome was production of a PPS molecular species with consistent impurity profile in order to have similar physiological effect.
It has been identified that the marketed Elmiron® is having about <7.0% of sugar impurities, however when some of the prior art processes were checked they were found to result in PPS having >11%. To date, there has been no discussion in the prior art regarding the relative importance of the sugar impurities in the Xylan and eventually in PPS. The prior art does not address the impurity profile or the quality of Xylan that is required for preparation of PPS of desired quality.
None of the prior art references focuses on the delignification process in Xylan and its impact on the quality of Xylan and eventually on PPS with regard of various sugar impurities. The purity of intermediate compounds play a major role in deciding the quality for final compound, especially in case of polymers. Therefore, there remains a need to prepare compounds of Formula I of high purity and in good yield, while overcoming the drawbacks presented by the processes described in the art.
The present application provides an improved process for obtaining high quality xylan and its use in the preparation of desired quality PPS. The present invention also provides improvements in the sulfation process and subsequent depolymerisation to yield PPS having desired degree of sulfation and pyridinium content.

SUMMARY OF THE INVENTION
In first embodiment, the present application provides improved processes for preparation of Pentosan Polysulfate Sodium (PPS) of Formula I,

the process comprising;
a) Isolation of xylan from Beech wood under suitable conditions;
b) Sulfation of xylan with pyridine-sulphur trioxide complex under suitable conditions to afford compound of Formula II;

c) Depolymerisation of xylan sulphate obtained in step b), under suitable conditions;
d) Isolation and recovery of PPS of Formula I.

In second embodiment, the present application provides the compound of Formula I having degree of sulfation 38-48%, acetyl content <3%, Total sugar impurities < 7%, single maximum known sugar impurity <3%, pyridinium content < 1%.
In third embodiment, the present application provides improved processes for the isolation of Xylan of Formula (III),

the process comprising;
a) First delignification of Xylan from Beechwood in presence of water at temperature about 100-150oC;
b) Second delignification in presence of 30% H2O2 at temperature about 100-150oC;
c) Treating the compound obtained from step b) with aqueous dilute alkali under suitable conditions;
d) Adjusting the pH of the filtrate from step c) to about 10-12 with aqueous dilute alkali at suitable temperature;
e) Isolating and recovering the desired compound of Formula III, by filtration, washing and drying.
In fourth embodiment, the present application provides the compound of Formula III having acetyl content <10%, total sugar impurities <7%, single maximum known sugar impurity <3%.

DETAILED DESCRIPTION OF THE INVENITON
In first embodiment, the present application provides improved processes for preparation of Pentosan Polysulfate Sodium (PPS) of Formula I,

the process comprising;
a) Isolation of xylan from Beech under suitable conditions;
b) Sulfation of xylan with suitable sulphating agents under suitable conditions to afford compound of Formula II;
c) Depolymerisation of xylan sulphate obtained in step b), under suitable conditions;
d) Isolation and recovery of PPS of Formula I.
The step a) involves treatment of beech wood in water at higher temperature for a suitable time. The temperature can be about 100-150oC, more preferably about 130oC. The process additionally involves a second delignification step in presence of hydrogen peroxide at temperatures between about 100-150oC, more preferably about 130oC.
Suitable time for delignification process in step a) can be anything < about 10 hours, more preferably < about 6 hours.

Step b) involves sulfation of xylan obtained in step a) with suitable sulphating agents.
The suitable sulphating agents can be selected from but not limited to pyridine sulphur trioxide, chlorosulfonic acid, N,N-dimethyl formamide-sulphur trioxide, 1,4-dioxane sulphur trioxide, TEA-sulphur trioxide, Sulfamic acid and like. In a preferred embodiment, pyridine sulphur trioxide complex is employed.
The suitable temperature for the said step may be less than about 60°C, or less than about 40°C, or less than about 20°C, or any other suitable temperatures.
The desired compound can be isolated by using pH adjustment with 25% aqueous sodium hydroxide solution and acetic acid.

Step c) involves depolymerisation of xylan sulphate obtained in step b), under suitable conditions;
The suitable temperature for the said step may be less than about 80°C, or less than about 60°C or any other suitable temperatures.
The pH of the mixture in said step may be less < about 4.0, more preferably < about 2.5 or any other suitable pH.
Depolymerization can also be done in presence of metal salts such as copper (II) acetate, Ferric Chloride.
Suitable time for depolymerisation process in step a) can be anything < about 10 hours, or < about 6 hours, more preferably < about 4 hours.

Step d) involves Isolation and recovery of PPS.
The desired compound can be isolated by pH adjustment with 25% aqueous NaOH solution followed by isolation using suitable solvents.
The compounds at various stages of the process may be recovered using conventional techniques known in the art. For example, useful techniques include, but are not limited to, decantation, centrifugation, gravity filtration, ultrafiltration, suction filtration, evaporation, flash evaporation, simple evaporation, rotational drying, spray drying, thin-film drying, freeze-drying, by addition of suitable anti-solvent and the like. The isolation may be optionally carried out at atmospheric pressure or under a reduced pressure. The solid that is obtained may carry a small proportion of occluded mother liquor containing a higher than desired percentage of impurities and, if desired, the solid may be washed with a solvent to wash out the mother liquor. Evaporation as used herein refers to distilling a solvent completely, or almost completely, at atmospheric pressure or under a reduced pressure. Flash evaporation as used herein refers to distilling of solvent using techniques including, but not limited to, tray drying, spray drying, fluidized bed drying, or thin-film drying, under atmospheric or a reduced pressure.
A recovered solid may optionally be dried. Drying may be suitably carried out using equipment such as a tray dryer, vacuum oven, air oven, fluidized bed dryer, spin flash dryer, flash dryer, and the like, at atmospheric pressure or under reduced pressure. Drying may be carried out at temperatures less than about 150°C, less than about 100°C, less than about 60°C, or any other suitable temperatures, in the presence or absence of an inert atmosphere such as nitrogen, argon, neon, or helium. The drying may be carried out for any desired time periods to achieve a desired purity of the product, such as, for example, from about 1 hour to about 15 hours, or longer.
In second embodiment, the present application provides the compound of Formula I having degree of sulfation 42-48%, acetyl content < 3%, Total sugar impurities < 7%, single maximum known sugar impurity < 3%, pyridinium content < 1%.
In third embodiment, the present application provides improved processes for the isolation of Xylan of Formula (III),

the process comprising;
a) First delignification of Xylan from Beech in presence of water at temperatures about 100-150oC;
b) Second delignification in presence of 30% H2O2 at temperatures about 100-150oC,
c) Treating the compound obtained from step b) with aqueous dilute alkali under suitable conditions,
d) Adjusting the pH of the filtrate from step c) to about 10-12 with aq. dilute alkali solution at suitable temperature,
e) Isolating and recovering the desired compound of Formula III, by filtration, washing and drying.
The step a) involves treatment of beech wood in water at higher temperature for a suitable time. The temperature can be between about 100-150oC, more preferably at about 130oC.
Suitable time for delignification process in step a) can be anything < about 6 hours, more preferably < about 4 hours.
After the reaction, the mixture was cooled to less than about 80oC, more preferably less than about 60oC and desired compound is isolated by filtration.
The step b) involves second delignification step in presence of hydrogen peroxide at temperatures between about 100-150oC, more preferably at about 130oC.
Suitable time for delignification process in step a) can be anything < about 6 hours, more preferably < about 4 hours.
After the reaction, the mixture was cooled to less than about 80oC, more preferably less than about 60oC and desired compound is isolated by filtration.

The step c) involves treating the compound obtained in step b) with aqueous dilute alkali solution at a suitable temperature.
The suitable temperature for the said step may be between about 80-200°C, or between about 120-180°C or any other suitable temperatures.
The aqueous dilute alkali may be any suitable base. In a preferred embodiment, aqueous sodium hydroxide (=25%) was employed.
Suitable time for step c) can be anything < about 10 hours, more preferably < about 6 hours.
After the reaction, the mixture was cooled to less than about 80oC, more preferably less than about 60oC and mixture was subjected to filtration and filtrate was used for next step.

The step d) involves adjusting the pH of the filtrate from step c) to about 10-12 with aqueous dilute alkali solution at suitable temperature.
The suitable temperature for the said step may be less than about 30°C, or less than about 10°C or any other suitable temperatures.
The aqueous dilute alkali may be any suitable base. In a preferred embodiment, aqueous sodium hydroxide (=25%) was employed.

The step e) involves isolation and recovery of the desired compound of Formula III, by filtration, washing and drying.
The desired compound can be isolated by pH adjustment with acetic acid at suitable temperature followed by isolation using suitable solvents. In a preferred embodiment, isolation is affected by addition of suitable anti-solvent selected from alcohols like methanol, isopropanol.

The compounds at various stages of the process may be isolated using conventional techniques known in the art. For example, useful techniques include, but are not limited to, decantation, by addition of suitable anti-solvent, centrifugation, gravity filtration, ultrafiltration, suction filtration, evaporation, flash evaporation, simple evaporation, rotational drying, spray drying, thin-film drying, freeze-drying, and the like. The isolation may be optionally carried out at atmospheric pressure or under a reduced pressure. The solid that is obtained may carry a small proportion of occluded mother liquor containing a higher than desired percentage of impurities and, if desired, the solid may be washed with a solvent to wash out the mother liquor. Evaporation as used herein refers to distilling a solvent completely, or almost completely, at atmospheric pressure or under a reduced pressure. Flash evaporation as used herein refers to distilling of solvent using techniques including, but not limited to, tray drying, spray drying, fluidized bed drying, or thin-film drying, under atmospheric or a reduced pressure. Anti-solvent refers to a liquid that, when combined with a solution of PPS/Xylan, reduces solubility of the PPS/Xylan in the solution, causing crystallization or precipitation in some instances spontaneously, and in other instances with additional steps, such as seeding, cooling, scratching, and/or concentrating.
A recovered solid may optionally be dried. Drying may be suitably carried out using equipment such as a tray dryer, vacuum oven, air oven, fluidized bed dryer, spin flash dryer, flash dryer, and the like, at atmospheric pressure or under reduced pressure. Drying may be carried out at temperatures less than about 150°C, less than about 100°C, less than about 60°C, or any other suitable temperatures, in the presence or absence of an inert atmosphere such as nitrogen, argon, neon, or helium. The drying may be carried out for any desired time periods to achieve a desired purity of the product, such as, for example, from about 1 hour to about 15 hours, or longer.
In fourth embodiment, the present application provides the compound of Formula III having acetyl content < 10%, total sugar impurities < 7%, single maximum known sugar impurity < 3%.

DEFINITIONS
The following definitions are used in connection with the present application unless the context indicates otherwise.
The term “about” when used in the present application preceding a number and referring to it, is meant to designate any value which lies within the range of ±10%, preferably within a range of ±5%, more preferably within a range of ±2%, still more preferably within a range of ±1% of its value. For example “about 10” should be construed as meaning within the range of 9 to 11, preferably within the range of 9.5 to 10.5, more preferably within the range of 9.8 to 10.2, and still more preferably within the range of 9.9 to 10.1.
An “alcohol” is an organic compound containing a carbon bound to a hydroxyl group. “C1-C6 alcohols” include, but are not limited to, methanol, ethanol, 2-nitroethanol, 2-fluoroethanol, 2,2,2-trifluoroethanol, hexafluoroisopropyl alcohol, ethylene glycol, 1-propanol, 2-propanol (isopropyl alcohol), 2-methoxyethanol, 1-butanol, 2-butanol, i-butyl alcohol, t-butyl alcohol, 2-ethoxyethanol, diethylene glycol, 1-, 2-, or 3-pentanol, neo-pentyl alcohol, t-pentyl alcohol, isoamyl alcohol, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, cyclohexanol, phenol, glycerol, or the like.
A “polar aprotic solvent” has a dielectric constant greater than 15 and includes: amide-based organic solvents, such as hexamethyl phosphoramide (HMPA), hexamethyl phosphorus triamide (HMPT), and N-methylpyrrolidone, nitro-based organic solvents, such as nitromethane, nitroethane, nitropropane, and nitrobenzene; ester-based organic solvents, such as ?-butyrolactone, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, and propiolactone; pyridine-based organic solvents, such as pyridine and picoline; and sulfone-based solvents, such as dimethylsulfone, diethylsulfone, diisopropylsulfone, 2-methylsulfolane, 3-methylsulfolane, 2,4-dimethylsulfolane, 3,4-dimethylsulfolane, 3-sulfolane, and sulfolane.
A “nitrile” is an organic compound containing a cyano -(C=N) bonded to another carbon atom. “C2-C6 Nitriles” include, but are not limited to, acetonitrile, propionitrile, butanenitrile, or the like.
Any organic solvents may be used alone, or any two or more may be used in combination, or one or more may be used in combination with water in desired ratios.
Acid addition salts are typically pharmaceutically acceptable, non-toxic addition salts with “suitable acids,” including, but not limited to: inorganic acids such as hydrohalic acids (for example, hydrofluoric, hydrochloric, hydrobromic, and hydroiodic acids) or other inorganic acids (for example, nitric, perchloric, sulfuric, and phosphoric acids); organic acids, such as organic carboxylic acids (for example, xinafoic, oxalic, propionic, butyric, glycolic, lactic, mandelic, citric, acetic, benzoic, 2- or 4-methoxybenzoic, 2- or 4-hydroxybenzoic, 2- or 4-chlorobenzoic, salicylic, succinic, malic, hydroxysuccinic, tartaric, fumaric, maleic, hydroxymaleic, oleic, and glutaric acids), organic sulfonic acids (for example, methanesulfonic, trifluoromethanesulfonic, ethanesulfonic, 2-hydroxyethanesulphonic, benzenesulfonic, toluene-p-sulfonic, naphthalene-2-sulphonic, and camphorsulfonic acids), and amino acids (for example, ornithinic, glutamic, and aspartic acids).
All percentages and ratios used herein are by weight of the total composition and all measurements made are at about 25°C and about atmospheric pressure, unless otherwise designated. All temperatures are in degrees Celsius unless specified otherwise. As used herein, “comprising” means the elements recited, or their equivalents in structure or function, plus any other element or elements which are not recited. The terms “having” and “including” are also to be construed as open ended. All ranges recited herein include the endpoints, including those that recite a range “between” two values. Whether so indicated or not, all values recited herein are approximate as defined by the circumstances, including the degree of expected experimental error, technique error, and instrument error for a given technique used to measure a value.
Terms such as "about," "generally," "substantially," and the like are to be construed as modifying a term or value such that it is not an absolute. Such terms will be defined by the circumstances and the terms that they modify as those terms are understood by those of skill in the art. This includes, at the very least, the degree of expected experimental error, technique error and instrument error for a given technique used to measure a value.
As used herein, the term "overnight" refers to a time interval from about 14 hours to about 24 hours, or about 14 hours to about 20 hours, for example, about 16 hours.
When a molecule or other material is identified herein as "pure", it generally means, unless specified otherwise, that the material has 98% purity or higher, as determined using methods conventional in the art such as high performance liquid chromatography (HPLC), gas chromatography (GC), or spectroscopic methods. In general, this refers to purity with regard to unwanted residual solvents, reaction by-products, impurities, and unreacted starting materials. In the case of stereoisomers, "pure" also means 98% of one enantiomer or diastereomer, as appropriate. "Substantially pure” refers to the same as "pure,” except that the lower limit is about 98% purity or higher and, likewise, "essentially pure” means the same as "pure" except that the lower limit is about 97% purity.
The sugar impurities, degree of sulfation, pyrodinium content can be determined by by techniques suh as ion chromatography, NMR.
Certain specific aspects and embodiments of the present application will be explained in greater detail with reference to the following examples, which are provided only for purposes of illustration and should not be construed as limiting the scope of the application in any manner. Reasonable variations of the described procedures are intended to be within the scope of the present invention. While particular aspects of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.

EXAMPLES
Example 1: Isolation of Xylan
600 g of Beech wood saw dust in water (~5 L) was treated at ~130oC for 3-4 hours followed by cooling and filtering, washing with water (3 L) and drying. The filtered mass was taken in 30% aq. H2O2 (30 mL), water (3.6 L) and stirred at between ~100-130oC for 3-4 hours followed by cooling and filtering, washing with water (3 L). The filtered mass was treated with 25% aq. NaOH solution (18 mL) and water (~5 L) at between ~130-160oC for 2-3 hours followed by cooling and filtering. The filtrate was cooled to 10-15oC and pH was adjusted to about 7.0-7.5 by using 25% aq. NaOH solution (~12 mL) and then to ~11.0 with 25% aq. NaOH solution (~5 mL) and maintenance of mixture at the same temperature for about 4-5 hours. Then again the pH was adjusted to ~7.4 with Acetic acid at 10-15oC followed by addition of isopropanol (~23 L) at 5-10oC. The solid so obtained was isolated by filtration, washed with isopropanol (250 mL), Methyl tert-butyl ether (250 mL). The solid was slurried in Methyl tert-butyl ether (250 mL) at ~45oC followed by cooling to 25-35oC and isolation by filtration, washing with MTBE and then dried under vacuum for overnight at about 60oC. Acetyl content: ~6.21%, Single maximum known < 2%, Total sugar impurities < 4%,

Example 2: Isolation of Xylan
140 g Beech wood saw dust in water (~1 L) was treated at ~110oC for 3-4 hours followed by cooling and filtering, washing with water (700 mL) and drying. The filtered mass (151 g) was taken in 30% aq. H2O2 (~5 mL), water (~ 1 L) and stirred at between ~110oC for 3-4 hours followed by cooling and filtering, washing with water (700 mL). The filtered mass (146 g) was treated with 25% aq. NaOH solution (~4 mL) and water (~1 L) at between ~150-160oC for 2-3 hours followed by cooling and filtering. The filtrate was cooled to 10-15oC and pH was adjusted to about 7.0-7.5 by using 25% aq. NaOH solution and then to ~11.0 with 25% aq. NaOH solution and maintenance of mixture at the same temperature for about 4 hours. Then again the pH was adjusted to ~7.2 with acetic acid at 10-15oC followed by addition of isopropanol (~5 L) at 5-10oC. The solid so obtained is isolated by filtration, washed with isopropanol (~490 mL), Methyl tert-butyl ether (~490 mL). The solid was slurried in Methyl tert-butyl ether (70 mL) at ~45oC followed by cooling to 25-35oC and isolation by filtration, washing with MTBE (70 mL) and then dried under vacuum for overnight at about 60oC. Single maximum known < 3%, Total sugar impurities < 5%,

Example 3: Isolation of Xylan
2.5 kg Beech wood dust in water (~24 L) was treated at ~125-130oC for 3-4 hours followed by cooling and filtering, washing with water (15 L) and drying. The filtered mass (2 Kg) was taken in 30% aq. H2O2 (~80 mL), water (~ 16 L) and stirred at between ~120-130oC for 3-4 hours followed by cooling and filtering, washing with water (10 L). The filtered mass (~ 2 Kg) was treated with 25% aq. NaOH solution (~60 mL) and water (~16 L) at between ~150-160oC for 2-3 hours followed by cooling and filtering. The filtrate was cooled to 10-15oC and pH was adjusted to about 7.0-7.5 by using 25% aq. NaOH solution for further reaction.

Example 4: Isolation of Xylan
140 g Beech wood dust was taken in 30% aq. H2O2 (~5 mL), water (~ 1 L) and stirred at between ~140oC for 3-4 hours followed by cooling and filtering, washing with water (700 mL). The filtered mass (122 g) was treated with 25% aq. NaOH solution (~4 mL) and water (~1 L) at between ~150-160oC for 2-3 hours followed by cooling and filtering. The filtrate was cooled to 10-15oC and pH was adjusted to about 7.0-7.5 by using 25% aq. NaOH solution and then to ~11.0 with 25% aq. NaOH solution and maintenance of mixture at the same temperature for about 4 hours. Then again the pH was adjusted to ~7.2 with acetic acid at 10-15oC followed by addition of isopropanol (~5 L) at 5-10oC. The solid so obtained was isolated by filtration, washed with isopropanol (~490 mL), Methyl tert-butyl ether (~490 mL). The solid was slurried in Methyl tert-butyl ether (70 mL) at ~45oC followed by cooling to 25-35oC and isolation by filtration, washing with MTBE (30 mL) and then dried under vacuum for overnight at about 60oC. Single maximum known < 2%, Total sugar impurities < 4%,

Example 5: Sulfation of Xylan
A mixture pyridine-sulphur trioxide complex was prepared by slow addition of chlorosulfonic (22 mL) acid to pyridine (80.6 mL) and N,N-dimethyl formamide (80 mL) at ~5-10oC. This mixture was heated to ~35oC, xylan (10 g, obtained in example 1) was added and mixture was maintained at ~40oC for ~4 hours followed by cooling of mixture to 30oC. To this mixture, Methanol (450 mL) was added and solid obtained was filtered and washed with methanol (100 mL). The solid was dissolved in water (30 mL) and mixture was cooled to 5-10oC followed by addition of aq. 25% NaOH solution (20 mL) to attain the pH to ~10. The aqueous layer was extracted with isopropyl acetate (3x70 mL), then pH of aq. Layer was adjusted to pH ~6.9 with acetic acid. The said aq. layer was added to precooled methanol (100 mL) and maintained for 30 min. The solid obtained was filtered and washed with methanol (50 mL) followed by drying at ~60oC to afford the sulphated xylan having degree of sulfation as ~45.98%, Pyridinium content ~0.24%.

Example 6: Sulfation of Xylan
A mixture pyridine-sulphur trioxide complex was prepared by slow addition of chlorosulfonic (44 mL) acid to pyridine (161 mL) and N,N-dimethyl formamide (DMF, 160 mL) at ~0-10oC. This mixture was heated to ~35oC, xylan (20 g) was added and mixture was maintained at ~75oC for ~3 hours followed by cooling of mixture to 30oC. To this mixture, Methanol (900 mL) was added and solid obtained was filtered and washed with methanol (200 mL). The solid was dissolved in water (60 mL) and mixture was cooled to 0-5oC followed by addition of aq. 25% NaOH solution (40 mL) to attain the pH to ~10. The aqueous layer was extracted with isopropyl acetate (3x140 mL), then pH of aq. layer was adjusted to pH ~6.1 with acetic acid. The said aq. layer was added to precooled methanol (200 mL) and maintained for 15-20 min. The solid obtained was filtered and washed with methanol (100 mL) followed by drying at ~60oC to afford the sulphated xylan having degree of sulfation as ~44%.

Example 7: Sulfation of Xylan
A mixture pyridine-sulphur trioxide was prepared by slow addition of chlorosulfonic (27 mL) acid to pyridine (150 mL) <~30oC. To this mixture Xylan (10 g) was added and mixture was maintained at ~30oC for ~5 hours followed by cooling of mixture to 10oC. To this mixture, Methanol (450 mL) was added and solid obtained was filtered and washed with methanol (100 mL). The solid was dissolved in water (30 mL) and mixture was cooled to 0-5oC followed by addition of aq. 25% NaOH solution (20 mL) to attain the pH to ~10. The aqueous layer was extracted with isopropyl acetate (3x70 mL), then pH of aq. layer was adjusted to pH ~6.7 with acetic acid. The said aq. layer was added to precooled methanol (100 mL) and maintained for 30 min. The solid obtained was filtered and washed with methanol (50 mL) followed by drying at ~60oC to afford the sulphated xylan having degree of sulfation as ~44%.

Example 8: Sulfation of Xylan
A mixture pyridine-sulphur trioxide was prepared by slow addition of chlorosulfonic (27 mL) acid to pyridine (150 mL) <~30oC. To this mixture Xylan (10 g) was added and mixture was maintained at ~50±10oC for ~5 hours followed by cooling of mixture to 10oC. To this mixture, Methanol (450 mL) was added and the solid obtained was filtered and washed with methanol (100 mL). The solid was dissolved in water (30 mL) and mixture was cooled to 10±5oC followed by addition of aq. 25% NaOH solution (20 mL) to attain the pH ~5 to 7 then to pH ~9 to 10 with 25% aq. NaOH solution (~5 mL) 10±5oC. The aqueous layer was extracted with isopropyl acetate (3x70 mL) and then pH of aq. layer was adjusted to pH ~6.7 with acetic acid. The said aq. layer was added to methanol (100 mL) and isopropyl acetate (70 ml) and the reaction mass was cooled to 0±5oC. The solid obtained was filtered followed by drying at ~60oC to afford the sulphated xylan having degree of sulfation as ~44%.

Example 9: Sulfation of Xylan
To a mixture of pyridine (40 mL), N,N-dimethyl formamide (40 mL), Xylan (5 g) was added. This mixture was heated to ~65oC followed by addition of pyridine-sulphur trioxide (26.5 g) and maintenance for about 3 hours. The mixture was cooled to room temperature and top layer was decanted followed by addition of methanol (150 mL) which was also decanted. To the residue, water (15 mL) was added and mixture was cooled to 5oC and pH was adjusted to about 10 with aqueous alkali and then to pH ~6.0 with acetic acid. This solution was added to methanol (100 mL) and solid was isolated by filtration and then dried under vacuum at 60oC to afford the title compound having degree of sulfation as ~42%.

Example 10: Sulfation of Xylan
A mixture of pyridine (48 mL), N,N-dimethyl acetamide (48 mL) was cooled to -5oC to 5oC followed by addition of chlorosulfonic acid (12 mL). The reaction mixture was heated to ~75oC followed by addition of Xylan (6 g). The mixture was maintained at ~75oC for ~2.5 hours followed by cooling of mixture to 30oC. Then this mixture was added to methanol (270 mL) and stirred at 25-30oC for 15-20 minutes. The solid obtained was filtered and washed with methanol (100 mL). The solid was dissolved in water (16 mL) and mixture was cooled to 0-5oC followed by addition of aq. 25% NaOH solution (13 mL) to attain the pH to ~10. The aqueous layer pH was again readjusted to pH ~6.3 with acetic acid. The said aq. layer was added to precooled methanol (100 mL) and maintained for 10 min. The solid obtained was filtered and washed with methanol (150 mL) followed by drying at ~60oC to afford the sulphated xylan having degree of sulfation as ~41%.

Example 11: Preparation of PPS
Xylan sulphate sodium (10 g) was taken in water (20 mL) and subjected to distillation to remove traces of solvents and then treated with 30% H2O2 (20 mL) for about 10 minutes. Then the pH of the mixture was adjusted to ~2 using 2N sulphuric acid and heated to ~70-75oC, maintained at the same temperature. Again the pH was maintained at ~2.1 using aqueous sodium hydroxide solution and stirred at ~70-75oC for about 3-4 hours. The mixture was cooled to 0-5oC and then the pH was adjusted to ~7.0 by using 25% aq. NaOH solution. This mixture was added to pre-cooled IPA (200 mL), the solid obtained was triturated with IPA (25 mL), isolated and dried. Then the dried solid was taken in water (50 mL) and then subjected to complete distillation and dried at ~60oC for overnight to afford the title compound having degree of sulfation ~46%, acetyl content ~2%, total sugar impurities ~3.1%, single maximum known sugar impurity < 2%.

Example 12: Preparation of PPS
Xylan sulphate sodium (8 g) was taken in water (16 mL) and treated with 30% H2O2 (16 mL) for about 10 minutes. Then the pH of the mixture was adjusted to ~2 using 25% aqueous sulphuric acid and heated to ~70-75oC, maintained at the same temperature for about 7 hours. The mixture was cooled to 5oC and then again the pH was adjusted to ~7.05 at the same temperature. This mixture was added to pre-cooled IPA (150 mL), the solid obtained was triturated with methanol (15 mL), isolated and dried under vacuum at ~60oC to afford the title compound.

Example 13: Preparation of PPS
Xylan sulphate sodium (15 g) was taken in water (60 mL) and subjected to partial distillation to remove traces of solvents. To this mixture, copper (II) acetate hydrate (12 mg), 30% H2O2 (6 mL) were added and mixture was heated to ~40oC. Then the pH of the mixture was adjusted to ~4 using aqueous sodium hydroxide (25%) solution and maintained at ~40oC for about ~6 hours. The mixture was cooled to room temperature and then the pH was adjusted to ~7.0 by using 25% aq. NaOH solution. This mixture was added to pre-cooled IPA (600 mL), the solid obtained was slurried with IPA (600 mL), was filtered and washed with IPA (50 mL) and dried under vacuum at ~60oC to afford the title compound.

Example 14: Preparation of PPS
Xylan sulphate sodium (10 g) was taken in water (30 mL) and heated to ~90oC. To this a mixture of 5N sulphuric acid (0.5 mL) and 30% H2O2 (5 mL) were added. The mixture was maintained at the same temperature for ~4 hours. Then the pH of the mixture was adjusted to ~9.5 by using 25% aq. NaOH solution and then readjusted to pH ~5.6 with acetic acid. This mixture was added to pre-cooled methanol (100 mL), and the mixture was stirred at room temperature for ~ 1 hour. The solid obtained was filtered and washed with methanol (30 mL), and dried under vacuum at 50oC for overnight to afford the title compound.

Example 15: Preparation of PPS
Xylan sulphate sodium (8 g) was taken in water (16 mL) and treated with 30% H2O2 (16 mL) for about 10 minutes. Then the pH of the mixture was adjusted to ~2 using 25% aqueous sulphuric acid and heated to ~70-75oC, pH was maintained at ~2.1 using aqueous sodium hydroxide solution. The reaction mixture was maintained at the same temperature for about 7 hours. The mixture was cooled to 0-5oC and then the pH was adjusted to ~7.0 by using 25% aq. NaOH solution. This mixture was added to pre-cooled IPA (150 mL), the solid obtained was triturated with methanol (15 mL), isolated and dried under vacuum at ~60oC to afford the title compound.

Example 16: Preparation of PPS
Xylan sulphate sodium (8 g) was taken in water (16 mL) and treated with 30% H2O2 (16 mL) for about 10 minutes. Then the pH of the mixture was adjusted to ~2 using pyridine hydrogen sulphate and heated to ~70-75oC, pH was maintained at ~2.1 using pyrdine. The reaction mixture was maintained at the same temperature for about 7 hours. The mixture was cooled to 0-5oC and then the pH was adjusted to ~7.0 by using 25% aq. NaOH solution. This mixture was added to pre-cooled IPA (150 mL), the solid obtained was triturated with methanol (15 mL), isolated and dried under vacuum at ~60oC to afford the title compound.

Example 17: Preparation of PPS
Xylan sulphate sodium (8 g) was taken Sodium acetate acetic acid buffer solution (32 mL) and treated with 30% H2O2 (16 mL) for about 10 minutes. The reaction mass was heated to ~70-75oC for about 7 hours. The mixture was cooled to 0-5oC and then the pH was adjusted to ~7.0 by using 25% aq. NaOH solution. This mixture was added to pre-cooled IPA (150 mL), the solid obtained was triturated with methanol (15 mL), isolated and dried under vacuum at ~60oC to afford the title compound.
,CLAIMS:We Claim:
1. A process for preparation of Pentosan Polysulfate Sodium (PPS) of Formula I:

comprising steps of:
a) isolation of xylan from Beech wood under suitable conditions;
b) sulfation of xylan with suitable sulphating agents under suitable conditions to afford compound of Formula II;

c) depolymerisation of xylan sulphate obtained in step b), under suitable conditions;
d) isolation and recovery of PPS of Formula I.

2. The process according to claim 1, wherein suitable sulphating agents selected from group consisting from pyridine sulphur trioxide, chlorosulfonic acid, N,N-dimethyl formamide-sulphur trioxide and 1,4-dioxane sulphur trioxide, TEA-sulphur trioxide, sulfamic acid and the like.
3. The process according to claim 1, wherein the compound of formula I contains degree of sulfation 42-48%, acetyl content <3%, total sugar impurities < 7%, single maximum known sugar impurity <3%, pyridinium content < 1%.

4. A process for the isolation of Xylan of Formula (III),

comprising;
a) first delignification of Xylan from Beechwood in presence of water at temperature about 100-150oC;
b) second delignification in presence of 30% H2O2 at temperature about 100-150oC;
c) treating the compound obtained from step b) with aqueous dilute alkali under suitable conditions;
d) adjusting the pH of the filtrate from step c) to about 10-12 with aqueous dilute alkali at suitable temperature;
e) isolating and recovering the desired compound of Formula III by filtration, washing and drying.

5. The process according to claim 4, wherein the aqueous dilute alkali is selected from group consisting of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate and the like.

6. The process according to claim 4, wherein the compound of Formula III contains acetyl content <10%, total sugar impurities <7%, single maximum known sugar impurity <3%.