Methods for producing crystalline l-glufosinate ammonium monohydrate

Abstract

To provide methods for preparing crystalline L-glufosinate ammonium monohydrate.SOLUTION: The present invention provides methods that include forming a mixture comprising water, a water-miscible organic solvent, ammonium hydroxide, and a glufosinate starting material containing L-glufosinate ammonium and D-glufosinate ammonium. L-glufosinate ammonium monohydrate is crystallized and separated from the mixture, providing L-glufosinate ammonium monohydrate Form B. Compositions and methods employing the crystalline L-glufosinate ammonium monohydrate are also provided.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 62 / 834,675, filed April 16, 2019, and U.S. Provisional Patent Application No. 62 / 978,005, filed February 18, 2020, which are incorporated by reference in their entireties.

[0002] (Reference to sequence listing submitted as a text file via EFS-WEB) An official copy of the Sequence Listing has been submitted electronically via EFS-Web as an ASCII formatted Sequence Listing in the filename "ASP 021.PCT-Sequence-Listing-1184814.txt" created on March 26, 2020, having a size of 13,767 bytes, and is filed concurrently herewith. The Sequence Listing contained in this ASCII formatted document is a part of the present specification and is incorporated herein by reference in its entirety. [Background technology]

[0003] The biological activity of the individual molecules of a racemic substance is usually different, and in many cases only one of the two enantiomers shows significant activity. This is also true for D,L-glufosinate, a nonselective foliar-applied herbicide used in large quantities worldwide. L-glufosinate inhibits the glutamine synthetase enzyme in plants, which leads to plant death, while the D-glufosinate enantiomer has essentially no herbicidal activity (Ruhland et al. (2002) Environ. Biosafety Res. 1:29-37). Nearly all current commercial glufosinate production is racemic (Duke et al. 2010 Toxins 2:1943-1962), which means that only about half of the glufosinate applied to agricultural land is useful; the other half is an environmental burden without providing any benefit.

[0004] L-glufosinate can be produced by asymmetric chemical synthesis as disclosed in U.S. Patent Nos. 4,499,027, 5,420,329, 7,772,426, 7,795,464, and 8,076,503. Although these methods are technically feasible, none have proven commercially cost-effective compared to the production of racemic glufosinate. Resolution of the racemate can often be accomplished by forming a diastereomer or a diastereomeric salt with another chiral compound; an example of this technique used with alpha amino acids is disclosed in U.S. Patent No. 4,647,692. This technique can be used with quinine or cinchonine to resolve racemic glufosinate, as disclosed in U.S. Patent Nos. 5,767,309 and 5,869,668. WO 2018 / 108797 discloses the resolution of racemic glufosinate with (-)-ephedrine. However, ephedrine is subject to increasing regulation and control by most government agencies around the world to prevent its diversion to illicit methamphetamine production. Other methods have been disclosed in which the inactive D-glufosinate in racemic glufosinate is converted to the active L-glufosinate, as described in U.S. Pat. No. 9,834,802 and WO 2019 / 018406. For commercial production, L-glufosinate produced in a stable solid form is highly desirable. Thus, a method to exclusively produce the L-glufosinate enantiomer is desirable. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 4,499,027 [Patent Document 2] U.S. Patent No. 5,420,329 [Patent Document 3] U.S. Patent No. 7,772,426 [Patent Document 4] U.S. Patent No. 7,795,464 [Patent Document 5] U.S. Patent No. 8,076,503 [Patent Document 6] U.S. Patent No. 4,647,692 [Patent Document 7] U.S. Patent No. 5,767,309 [Patent Document 8] U.S. Patent No. 5,869,668 [Patent Document 9] WO 2018 / 108797 [Patent Document 10] U.S. Patent No. 9,834,802 [Patent Document 11] WO 2019 / 018406 [Non-patent literature]

[0006] [Non-Patent Document 1] Ruhland et al. (2002) Environ. Biosafety Res. 1:29-37 [Non-Patent Document 2] Duke et al. 2010 Toxins 2:1943-1962 Summary of the Invention

[0007] Compositions of crystalline L-glufosinate ammonium monohydrate, as well as methods for preparation and use are provided. In one aspect, the present disclosure provides a method for preparing crystalline L-glufosinate ammonium monohydrate, the method comprising the following steps: (i) forming a mixture comprising a glufosinate starting material and an aqueous solution, the glufosinate starting material comprises L-glufosinate ammonium and D-glufosinate ammonium, the aqueous solution comprises water, a water-miscible organic solvent, and optionally an ammonia source, such as ammonium hydroxide; Above step; (ii) crystallizing L-glufosinate ammonium monohydrate from the mixture of step (i) to form L-glufosinate ammonium monohydrate crystals; and (iii) after step (ii), separating at least a portion of the L-glufosinate ammonium monohydrate crystals from the aqueous solution; thereby preparing crystalline L-glufosinate ammonium monohydrate; wherein the crystalline L-glufosinate ammonium monohydrate comprises L-glufosinate ammonium monohydrate form B.

[0008] In some embodiments, L-glufosinate seed crystals are used in the crystallization step of step (ii).

[0009] Further described herein is a method for the desalting and final isolation of crystalline L-glufosinate ammonium monohydrate. The method for obtaining L-glufosinate in crystalline form may include obtaining crystalline L-glufosinate from any racemic mixture of glufosinate. Thus, the method described herein can also be used to obtain crystalline L-glufosinate after enzymatic conversion of D-glufosinate to L-glufosinate. During the production of a mixture containing L-glufosinate, as described in US 9,834,802; US 10,260,078; and PCT / US2018 / 042503 (incorporated herein by reference in its entirety), the solution may be subjected to the following method to obtain an L-glufosinate mixture enriched in L-glufosinate. In this way, any D- and L-glufosinate mixture can be subjected to the method described herein to obtain crystalline L-glufosinate. Such a method may include the following steps:

[0010] Method I: Desalting. The desalting method comprises the following steps: (i) charging a reactor with a mixture comprising the glufosinate starting material and an aqueous solution and agitating the mixture; (ii) adjusting the pH of the solution to pH 6-7 using an "ammonia source"; (iii) concentrating the resulting solution under reduced pressure in a reactor at a jacket temperature of about 70° C. until the total dissolved solids concentration is at least 20-70 wt % (e.g., 30-60 wt %, 40-50 wt %, or 45-50 wt %); (iv) cooling the mixture to 2-15°C and separating the ammonium sulfate crystals using filtration or centrifugation, followed by adding methanol to the remaining solution to promote the formation of further ammonium sulfate crystals, which are separated, for example, using filtration or centrifugation; (v) drying the filtrate or the supernatant solution obtained after filtration or centrifugation, respectively, with a flow of air or gas at ambient pressure or under reduced pressure, at ambient or elevated temperature to obtain the "L-glufosinate starting material" (utilized in the methods below). Any suitable "ammonia source" can be used, e.g., gaseous ammonia, ammonium hydroxide, ammonium carbonate, etc.

[0011] Method IIa: Final isolation. In one embodiment, the final isolation method comprises the following steps: (i) forming a mixture comprising an "L-glufosinate starting material" (optionally obtained from the desalting method described above) and an aqueous solution, The "L-glufosinate starting material" includes L-glufosinate ammonium and D-glufosinate ammonium, The aqueous solution comprises water and a water-miscible organic solvent. Above step; (ii) crystallizing L-glufosinate ammonium monohydrate from the mixture of step (i) to form L-glufosinate ammonium monohydrate crystals; and (iii) after step (ii), separating at least a portion of the L-glufosinate ammonium monohydrate crystals from the aqueous solution; It may include, This results in the preparation of crystalline L-glufosinate ammonium monohydrate; wherein the crystalline L-glufosinate ammonium monohydrate comprises L-glufosinate ammonium monohydrate form B.

[0012] In some embodiments, L-glufosinate seed crystals are used in step (ii).

[0013] Method IIb: Final isolation. In another embodiment, the above method comprises the steps of: (i) forming a mixture comprising a "glufosinate starting material" (optionally obtained from the desalting process described above) and an aqueous solution, The "glufosinate starting material" includes L-glufosinate ammonium and D-glufosinate ammonium, The aqueous solution comprises water, a water-miscible organic solvent and an "ammonia source" Above step; (ii) crystallizing L-glufosinate ammonium monohydrate from the mixture of step (i) to form L-glufosinate ammonium monohydrate crystals; and (iii) after step (ii), separating at least a portion of the L-glufosinate ammonium monohydrate crystals from the aqueous solution; It may include, This results in the preparation of crystalline L-glufosinate ammonium monohydrate; wherein the crystalline L-glufosinate ammonium monohydrate comprises L-glufosinate ammonium monohydrate Form B. Any suitable "ammonia source" can be used in this method, including, but not limited to, gaseous ammonia, ammonium hydroxide, and ammonium carbonate.

[0014] In some embodiments, L-glufosinate seed crystals are used in the crystallization step of step (ii).Crystalline L-glufosinate ammonium hydrate can be formulated into compositions useful for controlling undesirable vegetative growth in fields and other areas. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 shows X-ray powder diffraction (XRPD) data for L-glufosinate ammonium monohydrate form B. [Diagram 2] FIG. 2 shows thermogravimetric analysis (TGA) data for L-glufosinate ammonium monohydrate form B, which shows a characteristic endotherm with an onset at 123.4° C. [Diagram 3] FIG. 3 shows infrared (IR) spectroscopy data for L-glufosinate ammonium monohydrate form B. [Figure 4] FIG. 4 shows X-ray powder diffraction (XRPD) data for L-glufosinate ammonium monohydrate form A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Detailed Description of the Invention The present disclosure is based on the discovery that L-glufosinate ammonium monohydrate form B is useful for directly producing purified L-glufosinate from a mixture containing both L-glufosinate and D-glufosinate. As a result, the ammonium form of L-glufosinate is obtained in a single step without the need for a resolution step with a chiral agent or the need to add large amounts of acid or other undesirable substances. In some embodiments, L-glufosinate can be obtained from the enzymatic conversion method described in U.S. Pat. No. 9,843,802 and U.S. Pat. No. 10,260,078. In this method, D-amino acid oxidase (DAAO) and transaminase are used to convert D-glufosinate to the L form. These enzymes can be immobilized, for example, on polymer beads and reused from batch to batch.

[0017] US Patent No. 9,843,802 and US Patent No. 10,260,078 describe DAAO enzymes modified to improve enzymatic activity. Example 13 below describes additional mutant DAAO enzymes for use in the methods of the present invention. The first reaction is the conversion of D-glufosinate to 4-(hydroxy-methylphosphoryl)-2-oxobutanoic acid (PPO) by the DAAO enzyme.

[0018] L-glufosinate produced in a stable solid form is highly desirable for commercial production. Some forms of solid L-glufosinate are hygroscopic, and therefore extra measures must be taken to eliminate contact between these solid L-glufosinate forms and water vapor. Amorphous L-glufosinate solids have been observed to be particularly hygroscopic and often deliquesce when exposed to ambient air in the laboratory. The hygroscopicity of crystalline L-glufosinate P free acid is significantly lower than that of amorphous L-glufosinate P free acid. Several crystalline forms of L-glufosinate are disclosed in WO 2019 / 018406, and two of these forms (designated as "Form A" and "Form B") are identified in the present invention as L-glufosinate ammonium monohydrate crystals. The monohydrate crystals of Form A and Form B have lower hygroscopicity compared to the amorphous form of L-glufosinate and are therefore more suitable for commercial production.

[0019] It has been found that the method used to crystallize L-glufosinate ammonium as a monohydrate crystal can result in preferential crystallization of L-glufosinate ammonium from a mixture containing both L-glufosinate and D-glufosinate. Crystals obtained using this method from a glufosinate starting material containing relative amounts of L-glufosinate and D-glufosinate in a ratio above the "eutectic point" have high optical purity, i.e., the crystals contain a high ratio of L-glufosinate compared to D-glufosinate. In some instances, the crystalline solid contained no or only very small amounts of D-glufosinate. The mother liquor resulting from the crystallization is enriched in D-glufosinate and can be recovered and then converted to L-glufosinate by the methods described herein. Crystals obtained from glufosinate starting material below the eutectic point contain substantial amounts of both L-glufosinate and D-glufosinate, and in some instances, the ratios are not significantly different from racemic glufosinate ammonium. Described herein is a method for producing L-glufosinate ammonium monohydrate crystals with high optical purity and low hygroscopicity.

[0020] I. Methods for Separating Salts from the Glufosinate Starting Material Provided herein is a method for separating salts (also referred to herein as desalting) from the glufosinate starting material to provide an L-glufosinate starting material suitable for use in Method II disclosed below. The salts may be selected from the group consisting of sodium sulfate, ammonium sulfate, sodium chloride, ammonium chloride, sodium citrate, ammonium citrate, sodium carbonate, ammonium carbonate, sodium bicarbonate, ammonium bicarbonate, sodium formate, ammonium formate, sodium acetate, ammonium acetate, monosodium phosphate, disodium phosphate, monosodium phosphate, and diammonium phosphate.

[0021] Method I: Desalting. In the desalting method described herein, a mixture including the glufosinate starting material and an aqueous solution is charged to a reactor and agitation is initiated, where "glufosinate starting material" includes L-glufosinate ammonium, D-glufosinate ammonium and salts; and "aqueous solution" includes water and a water-miscible organic solvent. The pH of the solution can then be adjusted to pH 6-7 using an ammonia source (such as, but not limited to, gaseous ammonia, ammonium hydroxide, or ammonium carbonate). The resulting solution is concentrated under reduced pressure in the reactor at a jacket temperature of about 70° C. until the total dissolved solids concentration is at least 20-70% by weight, e.g., 30-60% by weight, 40-50% by weight, or 45-50% by weight. After concentration, the mixture is cooled to 10° C.-15° C., during which ammonium sulfate is allowed to crystallize. The mixture is further cooled to 4° C.-10° C. and stirred for at least 30 minutes. The mixture is then filtered or centrifuged to remove the ammonium sulfate crystals and aqueous filtrate 1 is isolated. The ammonium sulfate cake is washed with methanol and the methanol wash is set aside. Filtration can be performed using a Nutsche filter or any suitable filter as determined by one skilled in the art of filtering organic materials. Aqueous filtrate 1 is charged to a reactor and agitation is commenced. Optionally, previously isolated ammonium sulfate crystals are added to the mixture to act as seed crystals. Methanol is added to the reactor and the mixture is then cooled to 10°C-15°C. The methanol wash set aside from the previous step is added as part of the first methanol charge. A second portion of methanol is added to the reactor and the mixture is cooled to 4°C-10°C. The mixture is stirred at this temperature for at least 30 minutes. The mixture is filtered or centrifuged to remove the ammonium sulfate crystals. The resulting aqueous filtrate 2 is isolated. The ammonium sulfate cake is washed with methanol and the wash filtrate is combined with aqueous filtrate 2 to obtain a "glufosinate solution". This "glufosinate solution" may be dried at ambient or elevated temperature under ambient or reduced pressure using a stream of air or gas to obtain the "L-glufosinate starting material."

[0022] II. Method for preparing crystalline L-glufosinate ammonium monohydrate

[0023] Provided herein is a method for preparing crystalline L-glufosinate ammonium monohydrate. The crystalline L-glufosinate ammonium monohydrate comprises L-glufosinate ammonium monohydrate Form B.

[0024] Method IIa: Final isolation. In one embodiment, the final isolation method comprises the following steps: (i) forming a mixture comprising a glufosinate starting material, e.g., an "L-glufosinate starting material" optionally obtained from the desalting method described above, and an aqueous solution, the glufosinate starting material comprises L-glufosinate ammonium and D-glufosinate ammonium, The aqueous solution comprises water and a water-miscible organic solvent. Above step; (ii) crystallizing L-glufosinate ammonium monohydrate from the mixture of step (i) to form L-glufosinate ammonium monohydrate crystals; and (iii) after step (ii), separating at least a portion of the L-glufosinate ammonium monohydrate crystals from the aqueous solution; It may include, This prepares crystalline L-glufosinate ammonium monohydrate. In some embodiments, in step (ii), L-glufosinate seed crystals are used.

[0025] Method IIb: Final isolation. In another embodiment, a method for preparing crystalline L-glufosinate comprises the following steps: (i) forming a mixture comprising a glufosinate starting material and an aqueous solution, the glufosinate starting material comprises L-glufosinate ammonium and D-glufosinate ammonium, the aqueous solution comprises water, a water-miscible organic solvent and a source of ammonia; Above step; (ii) crystallizing L-glufosinate ammonium monohydrate from the mixture of step (i) to form L-glufosinate ammonium monohydrate crystals; and (iii) after step (ii), separating at least a portion of the L-glufosinate ammonium monohydrate crystals from the aqueous solution; It may include, This results in the preparation of crystalline L-glufosinate ammonium monohydrate.

[0026] The molar ratio of L-glufosinate ammonium to D-glufosinate ammonium in the glufosinate starting material and the L-glufosinate starting material can vary depending on factors such as the method by which the glufosinate was synthesized or the extent of purification performed. The molar ratio of L-glufosinate ammonium to D-glufosinate ammonium can be, for example, about 50:50 to about 90:10, or about 55:45 to about 85:15, or about 60:40 to about 80:20, or about 65:35 to about 75:25. In some embodiments, the molar ratio of L-glufosinate ammonium to D-glufosinate ammonium in the glufosinate starting material and the L-glufosinate starting material is at least 50:50. In some embodiments, the molar ratio of L-glufosinate ammonium to D-glufosinate ammonium in the glufosinate and L-glufosinate starting materials is at least 70:30. In some embodiments, the molar ratio of L-glufosinate ammonium to D-glufosinate ammonium in the glufosinate and L-glufosinate starting materials is at least 76:24. In some embodiments, the molar ratio of L-glufosinate ammonium to D-glufosinate ammonium in the glufosinate and L-glufosinate starting materials is 50:50.

[0027] Other components, including impurities such as reaction by-products, may also be present in the glufosinate starting material. In some embodiments, the glufosinate starting material and the L-glufosinate starting material further comprise one or more components selected from the group consisting of L-glutamic acid and its salts, D-glutamic acid and its salts, L-pyroglutamic acid and its salts, 2-oxoglutaric acid and its salts, succinic acid and its salts, 2-oxo-4-(hydroxy(methyl)-phosphinoyl)butyric acid and its salts, sodium sulfate, ammonium sulfate, sodium chloride, ammonium chloride, sodium citrate, ammonium citrate, sodium carbonate, ammonium carbonate, sodium bicarbonate, ammonium bicarbonate, sodium formate, ammonium formate, sodium acetate, ammonium acetate, monosodium phosphate, disodium phosphate, monosodium phosphate, and diammonium phosphate. In some embodiments, the glufosinate starting material comprises L-glutamate.

[0028] While the number and amount of non-glufosinate components can vary, the amount of glufosinate in the glufosinate and L-glufosinate starting materials will be at least about 50% (w / w). The amount of glufosinate in the glufosinate and L-glufosinate starting materials can be, for example, at least 55% (w / w), or at least about 60% (w / w), or at least about 65% (w / w), or at least about 70% (w / w). The amount of glufosinate in the glufosinate starting material and the L-glufosinate starting material can be about 50% (w / w) to about 95% (w / w), or about 55% (w / w) to about 90% (w / w), or about 60% (w / w) to about 90% (w / w), or about 65% (w / w) to about 90% (w / w), or about 70% (w / w) to about 90% (w / w), or about 75% (w / w) to about 90% (w / w). In some embodiments, the amount of glufosinate in the glufosinate starting material and the L-glufosinate starting material is about 70% (w / w) to about 90% (w / w). In some embodiments, the amount of glufosinate in the glufosinate starting material and the L-glufosinate starting material is about 75% (w / w) to about 85% (w / w).

[0029] The aqueous solutions used in the methods of the present disclosure generally include water and a water-miscible organic solvent. By "miscible" it is meant that the organic solvent forms a homogeneous mixture with water without separating from the water or reacting chemically with the water. Examples of water-miscible organic solvents include, but are not limited to, C 1-6 Alkanols, such as methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, n-pentanol, cyclopentanol, and cyclohexanol; low molecular weight amides, such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and the like; ketones and ketone-alcohols, such as acetone, methyl ethyl ketone, cyclohexanone, and diacetone alcohol; water-miscible ethers, such as tetrahydrofuran, dioxane, and the like; and polyols, such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, polypropylene glycol, and 1,2,6-hexanetriol; and sulfoxides, such as dimethyl sulfoxide and sulfolane.

[0030] In some embodiments, the water-miscible solvent is selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, acetonitrile, tetrahydrofuran, 1,4-dioxane, 1-methyl-2-propanol, 1,2-propanediol, and 1,2-ethanediol. In some embodiments, the water-miscible organic solvent is methanol.

[0031] The ratio of water-miscible organic solvent to water in the aqueous solution can vary depending on factors such as the particular water-miscible organic solvent used or the amount of glufosinate to be purified. Typically, the amount of water-miscible organic solvent in the aqueous solution will be at least about 30% by volume. The ratio of water-miscible organic solvent to water in the aqueous solution can be, for example, about 30:70 to about 95:5, or about 35:65 to about 95:5, or about 40:60 to about 95:5, or about 45:55 to about 95:5, or about 50:50 to about 90:10, or about 55:45 to about 85:15, or about 60:40 to about 80:20, or about 65:35 to about 75:25.

[0032] In some embodiments, the ratio of the water-miscible organic solvent to water in the aqueous solution is about 45:55 to about 95:5 by volume. In some embodiments, the ratio of the water-miscible organic solvent to water in the aqueous solution is about 45:55 to about 65:35 by volume. In some embodiments, the ratio of the water-miscible organic solvent to water in the aqueous solution is about 45:55 to about 55:45. In some embodiments, the ratio of the water-miscible organic solvent to water in the aqueous solution is about 50:50. In some embodiments, the ratio of the water-miscible organic solvent to water in the aqueous solution is about 60:40.

[0033] The aqueous solution used in the above method generally contains an ammonia source such as gaseous ammonia or an ammonium salt such as ammonium hydroxide or ammonium carbonate at a concentration of several millimolar to 1 molar or more. For example, the concentration of ammonium hydroxide in the aqueous solution can be about 100 mM to about 750 mM, or about 200 mM to about 600 mM, or about 200 mM to about 550 mM, or about 250 mM to about 500 mM, or about 300 mM to about 450 mM, or about 325 mM to about 425 mM, or about 350 mM to about 400 mM, or about 350 mM to about 370 mM. In some embodiments, the concentration of ammonium hydroxide in the aqueous solution is about 0.1 M to about 1 M. In some embodiments, the concentration of ammonium hydroxide in the aqueous solution is 350 mM to about 450 mM. In some embodiments, the aqueous solution does not contain ammonium hydroxide. In some embodiments, the isolated crystals may comprise a mixture of form A crystals and form B crystals.

[0034] The L-glufosinate starting material and the aqueous solution are combined in amounts such that the concentration of glufosinate in the resulting mixture is suitable for glufosinate crystal formation. Typically, the molar concentration of glufosinate in the L-glufosinate starting material prior to crystallization will be at least 100 mM (e.g., 250 mM or more, or 500 mM or more, or 1 M or more). In some embodiments, the ratio of the L-glufosinate starting material to the aqueous solution in step (i) (methods IIa and IIb) is about 0.5:1 to about 5:1 by weight. In some embodiments, the ratio of the L-glufosinate starting material to the aqueous solution in step (i) (methods IIa and IIb) is about 1:1 to about 2:1 by weight. The ratio of L-glufosinate starting material to aqueous solution in step (i) (Methods IIa and IIb) can be, for example, about 1.1:1 by weight, or about 1.2:1 by weight, or about 1.3:1 by weight, or about 1.4:1 by weight, or about 1.5:1 by weight, or about 1.6:1 by weight, or about 1.7:1 by weight, or about 1.8:1 by weight, or about 1.9:1 by weight, or about 2:1 by weight.

[0035] The step of crystallizing L-glufosinate ammonium monohydrate may include heating a mixture comprising the starting material and an aqueous solution. The mixture may be heated to a temperature of about 40° C. to about 80° C. or higher, depending on factors such as, for example, the concentration of glufosinate in the mixture or the water-miscible organic solvent used in the aqueous solution. The mixture may be heated to a temperature of at least 40° C., or at least about 45° C., or at least about 50° C., or at least about 55° C., or at least about 60° C., or at least about 65° C., or at least about 70° C., or at least about 75° C., or at least about 80° C., or at least about 85° C., or at least about 90° C. In some embodiments, the mixture of step (i) (Methods IIa and IIb) is heated to a temperature of about 45° C. to about 55° C. and held at the elevated temperature for a period of about 5 minutes to about 24 hours. In some embodiments, the mixture of step (i) is heated to at least about 45° C. In some embodiments, the heated mixture is maintained at a temperature of at least 45° C. (e.g., at least 50° C., or at least 45° C.) for a period of about 10 minutes to about 6 hours before separating the L-glufosinate crystals from the mixture. In some embodiments, the heated mixture is maintained at about 45° C. or about 50° C. for at least about 1 hour. After heating, the mixture can be cooled (e.g., to a temperature of about 30° C. or less, e.g., about 25° C., or about 20° C., or about 4° C.).

[0036] Seed crystals containing glufosinate can be added to a heated or unheated mixture containing the starting material and an aqueous solution to promote the formation of L-glufosinate ammonium monohydrate crystals. Typically, the molar ratio of L-glufosinate to D-glufosinate (L:D ratio) in the seed crystals will be at least about 90:10. In some embodiments, the glufosinate seed crystals comprise L-glufosinate ammonium monohydrate form B. As described below, an L:D ratio of about 76:24 has been found to be the eutectic point above which L-glufosinate ammonium monohydrate can be efficiently crystallized from an aqueous mixture. Furthermore, the seed crystals containing L-glufosinate can be added in an amount such that the L:D ratio for the total amount of glufosinate in the system is at least 76:24.

[0037] The mixture containing the glufosinate seed crystals is generally maintained at a temperature for a period of time sufficient to form L-glufosinate ammonium monohydrate crystals, e.g., from a few minutes to a few days, at 25-50° C. In some embodiments, the mixture containing the glufosinate seed crystals is maintained at a temperature of about 30° C. for a period of about 1 hour to about 24 hours before separating the L-glufosinate ammonium monohydrate crystals from the mixture.

[0038] The glufosinate seed crystals can be added in an amount of, for example, about 0.05% (w / w) to about 0.1% (w / w), or about 0.1% (w / w) to about 0.5% (w / w), or about 0.5% (w / w) to about 1% (w / w), or about 1% (w / w) to about 5% (w / w), or about 5% (w / w) to about 10% (w / w), or about 10% (w / w) to about 20% (w / w), or about 20% (w / w) to about 30% (w / w). In some embodiments, the glufosinate seed crystals are added in an amount of about 0.05% (w / w) to about 30% (w / w) relative to the amount of glufosinate in the L-glufosinate starting material. In some embodiments, the glufosinate seed crystals are added in an amount of about 0.1% (w / w) to about 2.5% (w / w) relative to the amount of glufosinate in the L-glufosinate starting material. In some embodiments, the glufosinate seed crystals are added in an amount of about 0.1% (w / w) to about 0.5% (w / w) relative to the amount of glufosinate in the L-glufosinate starting material.

[0039] L-glufosinate ammonium monohydrate crystals can be conveniently separated from the aqueous mixture by filtration, centrifugation, or a combination thereof. In some embodiments, the crystals are isolated as a filter cake or centrifugation pellet, which can then be washed with water, a water-miscible solvent, or a combination thereof. The isolated crystals can be dried at ambient temperature or elevated temperature with a stream of air or gas (e.g., nitrogen or argon) under reduced pressure or at ambient pressure. For example, the crystals can be dried at a temperature of about 18-25°C, or about 25-40°C, or about 40-60°C, or about 60-70°C, or about 70-80°C, or about 80-90°C, or about 90-100°C. In some embodiments, the crystals are dried at 37°C. Drying can be monitored and stopped, for example, when the mass of the crystal sample is no longer reduced by evaporation of water or solvent. Large chunks of crystals can be milled to reduce lumping of the crystals. Thus, some embodiments of the present disclosure provide the above method, wherein separating at least a portion of the L-glufosinate ammonium monohydrate crystals in step (iii) comprises filtering the mixture of step (ii), centrifuging the mixture of step (ii), or a combination thereof.

[0040] The size range of crystalline L-glufosinate ammonium monohydrate particles obtained by using the methods provided herein is convenient for use in formulations. In some embodiments, the crystals are mixed with water and other formulation ingredients to form a herbicide product. In some embodiments, 90% of the crystalline L-glufosinate ammonium particles are within the range of 100-1500 nm as determined based on volume distribution measurements (i.e., "D v 90"), less than about 350 microns. For example, the D v 90 can be less than about 350 microns, or less than about 300 microns, or less than about 250 microns, or less than about 200 microns, or less than about 150 microns, or less than about 125 microns, or less than about 100 microns, or less than about 75 microns, or less than about 50 microns, or less than about 25 microns.

[0041] Advantageously, the crystalline L-glufosinate ammonium monohydrate prepared according to the methods provided herein is characterized by a high L:D ratio. Although the crystalline product may contain some D-glufosinate, the L:D ratio of the crystalline product is significantly higher than the L:D ratio of the glufosinate starting material. In some embodiments, the molar ratio of L-glufosinate to D-glufosinate in the crystalline L-glufosinate ammonium monohydrate product is at least 90:10. The molar ratio of L-glufosinate to D-glufosinate in the crystalline L-glufosinate ammonium monohydrate product can be, for example, at least 91:9, or at least 92:8, or at least 93:7, or at least 94:6, or at least 95:5, or at least 96:4, or at least 97:3, or at least 98:2, or at least 99:1.

[0042] The crystalline product has the following crystallinity values: 10.0, 11.4, 12.5, 16.5, 17.4, 18.1, 19.6, 20.0, 21.8, 22.9, 23.6, 24.0, 25.1, 25.5, 26.1, 26.3, 26.4, 27.9, 28.2, 28.4, 28.7, 29.2, 30.2, 30.9, 31.6, 31.7, 32.7, 33.0, 33.3, 34.3, 35.2, 36.7, 37.2, 37.4, 37.8, 38.3, 38.7, and 39.3 °2θ, ±0.2 L-glufosinate ammonium monohydrate form B can be identified based on an X-ray powder diffraction (XRPD) pattern showing at least three peaks selected from 10.0, 12.5, 16.5, 17.4, 18.1, 19.6, 20.0, 21.8, 22.9, 23.6, 24.0, 25.5, 26.3, 26.4, 29.2, 34.3, 35.2, and 37.4 °2θ, ±0.2 °2θ. In some embodiments, the XRPD pattern comprises at least 10 peaks selected from 10.0, 12.5, 16.5, 17.4, 18.1, 19.6, 20.0, 21.8, 22.9, 23.6, 24.0, 25.5, 26.3, 26.4, 29.2, 34.3, 35.2, and 37.4 °2θ, ±0.2 °2θ. In some embodiments, the XRPD pattern is substantially in accordance with FIG.

[0043] In some embodiments, L-glufosinate ammonium monohydrate form B is characterized by a differential scanning calorimetry (DSC) curve exhibiting an endotherm with an onset at about 123° C. In some embodiments, L-glufosinate ammonium monohydrate form B is characterized by a DSC curve substantially in accordance with Figure 2. In some embodiments, L-glufosinate ammonium monohydrate form B is characterized by an IR spectrum substantially in accordance with Figure 3.

[0044] A non-limiting example of the method according to the present disclosure can be carried out as follows: A solid L-glufosinate ammonium starting material containing at least 76.5% L-glufosinate ammonium and 23.5% D-glufosinate ammonium with a total glufosinate ammonium composition of about 75% by weight is charged into a suitable container. A mixture of water and methanol containing dilute ammonium hydroxide is added to the container; the ratio of methanol to water can be 70:30 to 50:50. The mixture is heated to about 50°C with stirring to ensure dissolution of the solids; further measures such as sonication can be used to aid dissolution. After aging the mixture for 1 hour, seed crystals of L-glufosinate ammonium hydrate ("Form B") are added to the mixture. The mixture is then cooled slowly and stepwise to 30°C and mixed for about 16 hours. The resulting slurry is drained from the container and centrifuged in portions. The resulting cake is washed with methanol; resuspension of the cake in methanol can also be included. After the second centrifugation, the solid is dried under ambient conditions.

[0045] III. Compositions Containing L-Glufosinate Monohydrate The crystalline L-glufosinate ammonium monohydrate described herein can be used in compositions useful for application to crop fields for the prevention or control of weeds. The compositions can be formulated as liquids for spraying on fields. The L-glufosinate is provided in an effective amount in the composition. For example, the amount of L-glufosinate ammonium monohydrate in the composition can be about 10 grams, about 50 grams, about 100 grams, about 150 grams, about 200 grams, about 250 grams, about 300 grams, about 350 grams, about 400 grams, about 450 grams, about 500 grams, about 550 grams, about 600 grams, about 650 grams, about 700 grams, about 750 grams, about 800 grams, about 850 grams, about 900 grams, about 950 grams, about 1,000 grams, about 1,050 grams, about 1,100 grams, about 1,150 grams, about 1,200 grams, about 1,250 grams, about 1,300 grams, about 1,350 grams, about 1,400 grams, about 1,450 grams, or about 1,500 grams of L-glufosinate per hectare.

[0046] The herbicide compositions described herein (including concentrates that require dilution prior to application to plants) contain L-glufosinate ammonium monohydrate (i.e., the active ingredient) and one or more adjuvant components in liquid or solid form. In some instances, the herbicide compositions also contain residual D-glufosinate and / or PPO.

[0047] The compositions are prepared by mixing the active ingredient with one or more adjuvants, such as diluents, extenders, carriers, surfactants, organic solvents, humectants, or conditioning agents, to provide a composition in the form of a finely divided particulate solid, pellets, solution, dispersion, or emulsion. Thus, the active ingredient may be used with an adjuvant, such as a finely divided solid, a liquid of organic origin, water, a wetting agent, a dispersing agent, an emulsifier, or any suitable combination thereof. In some embodiments, L-glufosinate ammonium monohydrate is present in an amount of about 10% (w / w) to 30% (w / w) based on the total weight of the formulated composition. From the standpoint of economy and convenience, water is the preferred diluent. However, not all compounds are resistant to hydrolysis, and in some instances, this hydrolysis may dictate the use of a non-aqueous solvent medium, as will be appreciated by those skilled in the art.

[0048] In some instances, the formulated composition may include one or more surfactants. Suitable surfactants for use in the formulated composition include, for example, sodium alkyl ether sulfate. The surfactant may be present in an amount of 10% (w / w) to 40% (w / w) by weight of the formulated composition. The formulated composition may optionally include one or more organic solvents. Optionally, the solvent may be 1-methoxy-2-propanol, dipropylene glycol, ethylene glycol, and mixtures thereof. The one or more solvents may be present in an amount of 0.5% (w / w) to 20% (w / w) by weight of the formulated composition.

[0049] The formulated composition may also include one or more polysaccharide humectants. Examples of suitable polysaccharide humectants include, for example, alkyl polysaccharides, pentoses, high fructose corn syrup, sorbitol, and molasses. Polysaccharide humectants, such as alkyl polysaccharides, may be present in the formulated composition in an amount of 4% (w / w) to 20% (w / w) by weight of the formulated composition. Diluents may also be included in the formulated composition. Suitable diluents include, for example, water and other aqueous components. Optionally, the diluent is present in an amount necessary to produce a composition ready for packaging or use.

[0050] The formulated compositions described herein, particularly liquids and soluble powders, may contain one or more surfactants as additional adjuvant components in sufficient amounts to make a given composition easily dispersible in water or oil. The incorporation of surfactants into compositions greatly enhances the effectiveness of those compositions. The surfactants used herein include, for example, wetting agents, dispersing agents, suspending agents, and emulsifying agents. Anionic agents, cationic agents, and nonionic agents can be used equally easily. Suitable wetting agents include, for example, alkylbenzene and alkylnaphthalene sulfonates, sulfated fatty alcohols, amines or acid amides, long-chain acid esters of sodium isothionate, esters of sodium sulfosuccinate, sulfated or sulfonated fatty acid esters, petroleum sulfonates, sulfonated vegetable oils, ditertiary acetylenic glycols, polyoxyethylene derivatives of alkylphenols (especially isooctylphenol and nonylphenol), and polyoxyethylene derivatives of mono-higher fatty acid esters of hexitol anhydrides (e.g., sorbitan). Exemplary dispersants include, for example, methyl cellulose, polyvinyl alcohol, sodium lignin sulfonate, polymeric alkylnaphthalene sulfonates, sodium naphthalene sulfonate, polymethylene bisnaphthalene sulfonate, and sodium N-methyl-N-(long chain acid) laurate.

[0051] Water-dispersible powder compositions can be made to include one or more active ingredients, inert solid fillers, and one or more wetting and dispersing agents. The inert solid fillers are usually of mineral origin, such as natural clays, diatomaceous earth, and synthetic minerals derived from silica. Examples of such fillers include, for example, kaolinite, attapulgite clay, and synthetic magnesium silicate. Aqueous suspensions can be prepared by dissolving or by mixing and grinding an aqueous slurry of water-insoluble active ingredients together in the presence of a dispersing agent to obtain a concentrated slurry of ultrafine particles. The resulting concentrated aqueous suspension is characterized by its extremely small particle size, which results in a very uniform coverage when diluted and sprayed. Emulsifiable oils are usually solutions of active ingredients in water-immiscible or partially water-immiscible solvents and surfactants. Suitable solvents for the active ingredients described herein include, for example, hydrocarbons and water-immiscible ethers, esters, or ketones. Additional ingredients suitable for use in the formulated compositions provided herein are described in WO 2019 / 018406 and U.S. Pat. Nos. 4,692,181 and 5,258,358, which are incorporated by reference in their entireties.

[0052] The formulated compositions described herein may also include other additives, such as fertilizers, phytotoxicants and plant growth regulators, pesticides, etc., used as adjuvants or in combination with any of the above adjuvants. The formulated compositions described herein can also be mixed with other materials, such as fertilizers, other phytotoxicants, etc., and applied in a single application.

[0053] It is recognized that the formulated herbicide composition can be used in combination with other herbicides.The herbicide composition described herein is often applied with one or more other herbicides to control a wider variety of undesirable vegetation.When used with other herbicides, the compound claimed in this application can be formulated with the other herbicide(s), tank-mixed with the other herbicide(s), or applied continuously with the other herbicide(s). Some of the herbicides that can be used with the formulated herbicide compositions described herein include the following: amide herbicides, such as allidochlor, 6-arylpicolinate, beflubutamid, benzadox, benzipram, bromobutide, cafenstrole, CDEA, chlorthiamid, 6-cyclopropylpicolinate, cyprazole, dimethenamid, dimethenamid- P (dimethenamid-P), diphenamid, epronaz, etnipromid, fentrazamide, flupoxam, fomesafen, halosaphen, isocarbamid, isoxaben, napro-pamide, naptalam, pethoxamid, propyzamide, quinonamid and tebutam; pyrimidinedione herbicides such as saflufenacil;Anilide herbicides, such as chloranocryl, cisanilide, clomeprop, cypromid, diflufenican, etobenzanid, fenasulam, flufenacet, flufenican, mefenacet, mefluidide, metamifop p), monalide, naproanilide, pentanochlor, picolinafen and propanil; arylalanine herbicides such as benzoylprop, flamprop and flamprop-M; chloroacetanilide herbicides such as acetochlor, alachlor, butachlor (b utachlor, butenachlor, delachlor, diethathyl, dimethachlor, metazachlor, metolachlor, S-metolachlor, pretilachlor, propachlor, propisochlor, prynachlor, terbuchlor terbuchlor, thenylchlor and xylachlor; sulfonanilide herbicides such as benzofluor, perfluidone, pyrimisulfan and profluazol; sulfonamide herbicides such as asulam, carbasulam, fenasulam and oryzalin;Antibiotic herbicides such as bilanafos; benzoic acid herbicides such as chloramben, dicamba, 2,3,6-TBA and tricamba; pyrimidinyloxybenzoic acid herbicides such as bispyribac and pyriminobac; pyrimidinylthiobenzoic acid herbicides such as pyrithiobac; phthalic acid herbicides such as chlorthal; picolinic acid herbicides such as aminopyralid, clopyralid and picloram; quinoline carboxylic acid herbicides such as quinclorac and quinmerac; arsenical herbicides such as cacodylic acid, CMA, DSM. A, hexaflurate, MAA, MAMA, MSMA, potassium arsenite and sodium arsenite; benzoylcyclohexanedione herbicides such as mesotrione, sulcotrione, tefuryltrione and tembotrione; alkylsulfonate benzofuranyl herbicides such as benfuresate and ethofumesate; carbamate herbicides such as asulam, carboxazole chlorprocarb, dichlormate, fenasulam, karbutilate and terbucarb;Carbanilate herbicides, such as barban, BCPC, carbasulam, carbetamide, CEPC, chlorbufam, chlorpropham, CPPC, desmedipham, phenisopham, phenmedipham, phenmedipham-ethyl, propham, and and swep; cyclohexene oxime herbicides such as alloxydim, butroxydim, clethodim, cloproxydim, cycloxydim, profoxydim, sethoxydim, tepraloxydim and tralkoxydim; cyclopropylisoxazole herbicides such as isoxazole, dicarboximide herbicides such as benzfendizone, cinidon-ethyl, flumezin, flumiclorac, flumioxazin and flumipropyn; dinitroaniline herbicides such as benfluralin, butralin, butralin, dinitramine, ethalfluralin, fluchloralin, isopropalin, methalpropalin, nitralin, oryzalin, pendimethalin, prodiamine, profluralin and trifluralin;Dinitrophenol herbicides such as dinofenate, dinoprop, dinosam, dinoseb, dinoterb, DNOC, etinofen and medinoterb; diphenyl ether herbicides such as ethoxyfen; nitrophenyl ether herbicides such as acifluorfen, aclonifen; en), bifenox, chlomethoxyfen, clomitrofen, etnipromid, fluorodifen, fluoroglycofen, fluoronitrofen, fomesafen, furyloxyfen, halosaphene, lactofen tofen, nitrofen, nitrofluorfen and oxyfluorfen; dithiocarbamate herbicides such as dazomet and metam; halogenated aliphatic herbicides such as arorac, chloropon, dalapon, flupropanate, hexachloroacetone, iodomethane, methyl bromide, monochloroacetone, iodomethane, methyl bromide, monochloroacetone, iodomethane, methyl bromine, monochloroacetone ... acetic acid, SMA and TCA; imidazolinone herbicides such as imazamethabenz, imazamox, imazapic, imazapyr, imazaquin and imazethapyr; inorganic herbicides such as ammonium sulfamate, borax, calcium chlorate, copper sulfate, ferrous sulfate, potassium azide, potassium cyanate, sodium azide, sodium chlorate and sulfuric acid;Nitrile herbicides such as bromobonil, bromoxynil, chloroxynil, dichlobenil, iodobonil, ioxynil and pyraclonil; organophosphate herbicides such as amiprofos-methyl, anilofos, bensulide, bilanafos, butamifos, 2,4-D EP, DMPA, EBEP, fosamine, glyphosate and piperophos; phenoxy herbicides such as bromofenoxim, clomeprop, 2,4-DEB, 2,4-DEP, difenopenten, disul, erbon, etnipromid, fenteracol and trifopsime; phenoxyacetic acid herbicides such as 4-CPA, 2,4-D, 3,4-DA, 2-methyl-4-chlorophenoxyacetic acid (MCPA), MCPA-thioethyl, and 2,4,5-T; phenoxybutyric acid herbicides such as 4-CPB, 2,4-DB, 3,4-DB, MCPB, and 2,4,5-TB; phenoxypropionic acid herbicides such as cloprop, 4-CPP, dichlorprop, dichlorprop-P, 3,4-DP, fenoprop, mecoprop, and mecoprop-P;Aryloxyphenoxypropionic acid herbicides, such as chlorazifop, clodinafop, clofop, cyhalofop, diclofop, fenoxaprop, fenoxaprop-P, fenthiaprop, fluazifop, fluazifop-P, fop-P, haloxyfop, haloxyfop-P, isoxapyrifop, metamifop, propaquizafop, quizalofop, quizalofop-P and trifop; phenylenediamine herbicides, such as dinitramine and prodiamine; amine); pyrazolyl herbicides such as benzofenap, pyrazolinate, pyrasulfotole, pyrazoxyfen, pyroxasulfone and topramezone; pyrazolylphenyl herbicides such as fluazolate and pyraflufen; pyridazine herbicides such as pyridazinone herbicides such as brompyrazon, chloridazone, dimidazon, flufenpyr, metflurazon, norflurazon, oxapyrazon and pydanon;Pyridine herbicides such as aminopyralid, cliodinate, clopyralid, dithiopyr, fluroxypyr, haloxydine, picloram, picolinafen, pyriclor, thiazopyr and triclopyr; pyrimidinediamine herbicides such as iprimidam and thioclorim; quaternary ammonium herbicides such as cyperquat, diethamquat, difenzo diquat, diquat, morphamquat, and paraquat; thiocarbamate herbicides such as butyrate, cycloate, di-allate, EPTC, esprocarb, ethiolate, isopolinate, methiobencarb, molinate, orbencarb, pebulate, prosulfocarb, pyributicarb, sulfalate; e), thiobencarb, thiocarbazil, triallate and vemolate; thiocarbonate herbicides such as dimexano, EXD and proxan; thiourea herbicides such as methiuron; triazine herbicides such as dipropetryn, triaziflam and trihydroxytriazine; Chlorotriazine herbicides, such as atrazine, chlorazine, cyanazine, cyprazine, eglinazine, ipazine, mesoprazine, procyazine, proglinazine, propazine, sebuthylazine, simazine, terbuthylazine, azine and trietazine; methoxytriazine herbicides such as atraton, methometon, prometon, secbumeton, simeton and terbumeton; methylthiotriazine herbicides such as ametryn, aziprotryne, cyanatryn, desmetryn, dimethametryn, thametryn, mesoprotryne, prometryn, simetryn and terbutryn; triazinone herbicides such as ametridione, amibuzin, hexazinone, isomethiozin, metamitron and metribuzin; triazole herbicides such as amitrole,cafenstrole, epronaz and flupoxam; triazolone herbicides such as amicarbazone, bencarbazone, carfentrazone, flucarbazone, propoxycarbazone, sulfentrazone and thiencarbazone-methyl ; triazolopyrimidine herbicides such as cloransulam, diclosulam, florasulam, flumetsulam, metosulam, penoxsulam and pyroxsulam; uracil herbicides such as butafenacil, bromacil, flupropacil, isocil, lenacil, il and terbacil; 3-phenyluracil; urea herbicides such as benzthiazuron, cumyluron, cycluron, dichloralurea, diflufenzopyr, isonoruron, isouron, methabenzthiazuron, monisouron and nona. noruron; phenylurea herbicides, such as anisuron, buturon, chlorbromuron, chloreturon, chlorotoluron, chloroxuron, daimuron, difenoxuron, dimefuron, diuron, fenuron, fluometuron,Fluothiuron, isoproturon, linuron, methiuron, methyldymron, metobenzuron, metobromuron, metoxuron, monolinuron, monuron, neburon, parafluron, phenobenzuron n), siduron, tetrafluron and thidiazuron; pyrimidinylsulfonylurea herbicides such as amidosulfuron, azimsulfuron, bensulfuron, chlorimuron, cyclosulfamuron, ethoxysulfuron, flazasulfuron, furuse Tosulfuron, flupyrsulfuron, foramsulfuron, halosulfuron, imazosulfuron, mesosulfuron, nicosulfuron, orthosulfamuron, oxasulfuron, primisulfuron, pyrazosulfuron razosulfuron, rimsulfuron, sulfometuron, sulfosulfuron and trifloxysulfuron; triazinylsulfonylurea herbicides such as chlorsulfuron, cinosulfuron, ethametsulfuron, iodosulfuron, metsulfuron,prosulfuron, thifensulfuron, triasulfuron, tribenuron, triflusulfuron and tritosulfuron; thiadiazolyl urea herbicides such as buthiuron, ethidimuron, tebuthiuron, thiazafluron and thidiazuron; diazuron; as well as unclassified herbicides, such as acrolein, allylalcohol, aminocyclopyrachlor, azafenidin, benazolin, bentazone, benzobicyclon, buthidazole, calcium cyanamide, cambendichlor, chlorfenac, ac), chlorfenprop, chlorflurazole, chlorflurenol, cinmethylin, clomazone, CPMF, cresol, ortho-dichlorobenzene, dimepiperate, endothal, fluoromidine, fluridone, flurochloridone done), flurtamone, fluthiacet, indanofan, methazole, methyl isothiocyanate, nipyraclofen, OCH, oxadiargyl, oxadiazon, oxaziclomefone, pentachlorophenol, pentoxazone, phenylmercuric acetate,Pinoxaden, prosulfalin, pyribenzoxim, pyriftalid, quinoclamine, rhodethanil, sulglycapin, thidiazimin, tridiphane, trimeturon, tripropindan and tritac. The herbicidal compositions of the present invention can also be used with glyphosate, dicamba or 2,4-D for glyphosate-tolerant, dicamba-tolerant or 2,4-D-tolerant crops. In general, it is preferred to use the compositions described herein in combination with herbicides that are selective for the crops treated and that complement the spectrum of weeds controlled by these compositions at the application rates used. It is more generally preferred to apply the compositions described herein and other complementary herbicides simultaneously, as a combined formulation, or as a tank mix.

[0054] IV. How to use The compositions described herein can be used in a method for selectively controlling weeds in fields or any other areas, such as railroad tracks, lawns, golf courses, and other locations where weed control is desired. Optionally, the fields or other areas can include planted seed crops or crops resistant to glufosinate. The method can include applying an effective amount of the composition comprising L-glufosinate described herein to the field.

[0055] The compositions described herein are useful for application to crop fields for the prevention or control of weeds. The compositions can be formulated as a liquid for spraying on fields. L-glufosinate is provided in the composition in an effective amount. As used herein, "effective amount" means about 10 grams active ingredient per hectare to about 1,500 grams active ingredient per hectare, for example, about 50 grams to about 400 grams or about 100 grams to about 350 grams. In some embodiments, the active ingredient is L-glufosinate. For example, the amount of L-glufosinate in the composition can be about 10 grams, about 50 grams, about 100 grams, about 150 grams, about 200 grams, about 250 grams, about 300 grams, about 350 grams, about 400 grams, about 500 grams, about 550 grams, about 600 grams, about 650 grams, about 700 grams, about 750 grams, about 800 grams, about 850 grams, about 900 grams, about 950 grams, about 1,000 grams, about 1,050 grams, about 1,100 grams, about 1,150 grams, about 1,200 grams, about 1,250 grams, about 1,300 grams, about 1,350 grams, about 1,400 grams, about 1,450 grams, or about 1,500 grams of L-glufosinate per hectare.

[0056] V. Illustrative Embodiments 1. A method for preparing crystalline L-glufosinate ammonium monohydrate, comprising the following steps: (i) forming a mixture comprising an L-glufosinate starting material and an aqueous solution, wherein the L-glufosinate starting material comprises L-glufosinate ammonium and D-glufosinate ammonium; The aqueous solution comprises water and a water-miscible organic solvent. Above step; (ii) crystallizing L-glufosinate ammonium monohydrate from the mixture of step (i) to form L-glufosinate ammonium monohydrate crystals; and (iii) after step (ii), separating at least a portion of the L-glufosinate ammonium monohydrate crystals from the aqueous solution; Including, This results in the preparation of crystalline L-glufosinate ammonium monohydrate. wherein the crystalline L-glufosinate ammonium monohydrate comprises L-glufosinate ammonium monohydrate form B; The above method.

[0057] 2. The method of embodiment 1, wherein the aqueous solution further comprises a source of ammonia.

[0058] 3. The method of embodiment 2, wherein the ammonia source is ammonium hydroxide.

[0059] 4. The method of any one of embodiments 1-3, wherein the molar ratio of L-glufosinate ammonium to D-glufosinate ammonium in the glufosinate starting material is at least 70:30.

[0060] 5. The method of any one of embodiments 1-4, wherein the molar ratio of L-glufosinate ammonium to D-glufosinate ammonium in the glufosinate starting material is at least 50:50.

[0061] 6. The method of any one of embodiments 1-4, wherein the molar ratio of L-glufosinate ammonium to D-glufosinate ammonium in the glufosinate starting material is at least 76:24.

[0062] 7. The method of any one of embodiments 1-6, wherein the L-glufosinate starting material further comprises one or more components selected from the group consisting of L-glutamic acid and its salts, D-glutamic acid and its salts, L-pyroglutamic acid and its salts, 2-oxoglutaric acid and its salts, succinic acid and its salts, 2-oxo-4-(hydroxy(methyl)phosphinoyl)butyric acid and its salts, sodium sulfate, ammonium sulfate, sodium chloride, ammonium chloride, monosodium phosphate, disodium phosphate, monoammonium phosphate, and diammonium phosphate.

[0063] 8. The method of embodiment 7, wherein the L-glufosinate starting material comprises L-glutamic acid.

[0064] 9. The method of any one of embodiments 1-8, wherein the amount of glufosinate in the L-glufosinate starting material is from about 70% (w / w) to about 90% (w / w).

[0065] 10. The method of embodiment 9, wherein the amount of glufosinate in the L-glufosinate starting material is from about 75% (w / w) to about 85% (w / w).

[0066] 11. The method of any one of embodiments 1-10, wherein the water-miscible solvent is selected from the group consisting of methanol, ethanol, 1-propanol, 2-propanol, acetonitrile, tetrahydrofuran, 1,4-dioxane, 1-methyl-2-propanol, 1,2-propanediol, and 1,2-ethanediol.

[0067] 12. The method of embodiment 11, wherein the water-miscible organic solvent is methanol.

[0068] 13. The method of any one of embodiments 1-12, wherein the ratio of the water-miscible organic solvent to water in the aqueous solution is from about 45:55 to about 95:5 by volume.

[0069] 14. The method of any one of embodiments 1-13, wherein the ratio of water-miscible organic solvent to water in the aqueous solution is from about 45:55 to about 65:35 by volume.

[0070] 15. The method of any one of embodiments 1-14, wherein the concentration of ammonium hydroxide in the aqueous solution is from about 0.1 M to about 1 M.

[0071] 16. The method of embodiment 15, wherein the concentration of ammonium hydroxide in the aqueous solution is about 0.4M.

[0072] 17. The method of any one of embodiments 1-16, wherein the ratio of L-glufosinate starting material to aqueous solution in step (i) is from about 0.5:1 to about 5:1 by weight.

[0073] 18. The method of embodiment 17, wherein the ratio of L-glufosinate starting material to aqueous solution in step (i) is from about 1:1 to about 2:1 by weight.

[0074] 19. The method of any one of the preceding embodiments, wherein step (ii) comprises heating the mixture of step (i) to form a heated mixture.

[0075] 20. The method of embodiment 19, wherein the mixture of step (i) is heated to at least about 45° C.

[0076] 21. The method of embodiment 19 or embodiment 20, wherein prior to step (iii), the heated mixture is maintained at a temperature of at least about 45° C. for a period of from about 10 minutes to about 6 hours.

[0077] 22. The method of any one of embodiments 19-21, further comprising, prior to step (iii), cooling the heated mixture to form a cooled mixture.

[0078] 23. The method of embodiment 22, wherein the heated mixture is cooled to a temperature of about 30° C. or less.

[0079] 24. The method of any one of embodiments 1-18, wherein step (ii) comprises adding glufosinate seed crystals to the mixture of step (i).

[0080] 25. The method of any one of embodiments 19-23, comprising adding glufosinate seed crystals to the heated mixture of step (ii).

[0081] 26. The method of embodiment 24 or embodiment 25, wherein the glufosinate seed crystals comprise L-glufosinate ammonium monohydrate Form B.

[0082] 27. The method of any one of embodiments 24-26, wherein the mixture containing the glufosinate seed crystals is maintained at a temperature of about 30° C. for a period of about 1 hour to about 24 hours prior to step (iii).

[0083] 28. The method of any one of embodiments 24-27, wherein the glufosinate seed crystals are added in an amount of about 0.05% (w / w) to about 30% (w / w) relative to the amount of glufosinate in the L-glufosinate starting material.

[0084] 29. The method of embodiment 28, wherein the glufosinate seed crystals are added in an amount of about 0.1% (w / w) to about 0.5% (w / w) relative to the amount of glufosinate in the L-glufosinate starting material.

[0085] 30. The method of any one of embodiments 1 to 29, wherein in step (iii), separating at least a portion of the L-glufosinate crystals comprises filtering the mixture of step (ii), centrifuging the mixture of step (ii), or a combination thereof.

[0086] 31. The method of any one of embodiments 1-30, further comprising one or more of the following steps: step (iv) washing the L-glufosinate ammonium monohydrate crystals; and step (v) drying the L-glufosinate ammonium monohydrate crystals.

[0087] 32. The method of any one of embodiments 1-31, wherein the crystalline L-glufosinate ammonium monohydrate further comprises D-glufosinate.

[0088] 33. The method of embodiment 32, wherein the molar ratio of L-glufosinate to D-glufosinate is at least 90:10.

[0089] 34. The method of embodiment 32 or embodiment 33, wherein the molar ratio of L-glufosinate to D-glufosinate is at least 95:5.

[0090] 35. L-glufosinate ammonium monohydrate form B has the following optical properties: 10.0, 11.4, 12.5, 16.5, 17.4, 18.1, 19.6, 20.0, 21.8, 22.9, 23.6, 24.0, 25.1, 25.5, 26.1, 26.3, 26.4, 27.9, 28.2, 28.4, 28.7, 29.2, 30.2, 30.9, 31.6, 31.7, 32.7, 33.0, 33.3, 34.3, 35.2, 36.7, 37.2, 37.4, 37.8, 38.3, 38.7, and 39.3 °2θ, ± 0.2, as measured by a diffractometer using Cu-Kα radiation. The method of any one of the preceding embodiments, characterized by an X-ray powder diffraction (XRPD) pattern comprising at least three peaks selected from °2θ.

[0091] 36. The method of any one of embodiments 1-35, wherein the L-glufosinate ammonium monohydrate form B is characterized by a differential scanning calorimetry (DSC) curve exhibiting an endotherm with an onset at about 123° C.

[0092] 37. Crystalline L-glufosinate ammonium monohydrate prepared by the method of any one of embodiments 1-36, comprising L-glufosinate ammonium monohydrate Form B.

[0093] 38. The crystalline L-glufosinate ammonium monohydrate according to embodiment 37, further comprising D-glufosinate.

[0094] 39. The crystalline L-glufosinate ammonium monohydrate according to embodiment 38, wherein the molar ratio of L-glufosinate to D-glufosinate is at least 90:10.

[0095] 40. The crystalline L-glufosinate ammonium monohydrate according to embodiment 38 or embodiment 39, wherein the molar ratio of L-glufosinate to D-glufosinate is at least 95:5.

[0096] 41. A method for preparing crystalline L-glufosinate from a glufosinate mixture, comprising the steps of: (i) Preparation of immobilized enzymes, said enzymes being D-amino acid oxidase (DAAO) enzymes and transaminase enzymes; (ii) contacting the glufosinate mixture with an immobilized enzyme to obtain an L-glufosinate-enriched composition; (iii) performing chromatographic purification of the composition of step (ii) to isolate L-glufosinate; The above method.

[0097] 42. A method for preparing crystalline L-glufosinate from a composition containing both D-glufosinate and L-glufosinate, the method comprising the steps of: (i) contacting the composition with a DAAO and a transaminase enzyme; (ii) performing an enzymatic reaction to obtain a composition of greater than 70% L-glufosinate; (iii) crystallizing L-glutamic acid from the composition of step (ii); (iv) chromatographic purification to obtain a composition comprising L-glufosinate; (v) desalting the composition of step (iv); and (vi) isolating L-glufosinate from the composition of step (v) by crystallization. The above method.

[0098] 43. A method for separating a salt from a glufosinate starting material, comprising the steps of: (i) dissolving the glufosinate starting material in an aqueous solution; (ii) adjusting the pH of the solution to 6-7; (iii) concentrating the solution to a total dissolved solids concentration of at least 20-70 wt% (e.g., 30-60 wt%, 40-50 wt%, or 45-50 wt%); (iv) cooling the concentrated solution to 2-15°C; (v) isolating the crystallized salt using filtration or centrifugation; and (vi) drying the remaining solution to isolate glufosinate ammonium monohydrate. The above method.

[0099] 44. The method of embodiment 43, wherein the salt is selected from the group consisting of ammonium sulfate, sodium sulfate, ammonium citrate, sodium citrate, ammonium carbonate, sodium carbonate, ammonium formate, sodium formate, ammonium acetate, sodium acetate, ammonium bicarbonate, and sodium bicarbonate.

[0100] 45. The method of embodiment 44, wherein the salt is ammonium sulfate.

[0101] 46. ​​The method of any one of embodiments 42 to 45, wherein the DAAO enzyme comprises the amino acid sequence set forth in SEQ ID NO:2.

[0102] 47. The method of any one of embodiments 42 to 45, wherein the DAAO enzyme comprises the amino acid sequence set forth in SEQ ID NO:3.

[0103] 48. A mutant DAAO enzyme comprising the amino acid sequence shown in SEQ ID NO:2.

[0104] 49. A mutant DAAO enzyme comprising the amino acid sequence shown in sequence number 3.

[0105] 50. A mutant DAAO enzyme comprising the amino acid sequence shown in sequence number 5.

[0106] The following examples are offered by way of illustration and not by way of limitation. EXAMPLES

[0107] VI. Working Examples Example 1. Characterization of Crystalline L-Glufosinate Ammonium Monohydrate Form B

[0108] Single crystal X-ray diffraction analysis provided the crystalline morphology and unit structure of L-glufosinate ammonium monohydrate form B referenced in Table 1:

[0109] [Table 1]

[0110] Analysis of the crystalline material by X-ray powder diffraction (XRPD) assigned the pattern in Figure 1 (top trace) to L-glufosinate ammonium monohydrate. This pattern is consistent with "Form B" in Figure 1 (bottom trace) that was crystallized and isolated in a previous study. Assay of ammonium content by ion chromatography and water content by Karl Fisher analysis indicates that the crystals, consistent with the XRPD pattern of "Form B," contain stochiometric amounts of water and ammonia (Table 2).

[0111] Characterization of the crystals by HPLC (AG-990-6-26) showed that the amount of glufosinate free acid was 76.29% (w / w). Glutamic acid was the major impurity at 0.47% (w / w). 2-oxoglutaric acid and L-pyroglutamic acid were present at <0.1% (w / w). Water, 7.50% (w / w); ammonia, 6.79% (w / w); sodium, 3.55% (w / w); and sulfate, 5.09% (w / w) made up the remaining mass in the crystalline material.

[0112] [Table 2]

[0113] Example 2. Characterization of Crystalline L-Glufosinate Ammonium Monohydrate Form A Single crystal X-ray diffraction analysis provided the crystalline morphology and unit structure of L-glufosinate ammonium monohydrate form A referenced in Table 3:

[0114] [Table 3]

[0115] Analysis of the crystalline material by X-ray powder diffraction (XRPD) assigned the pattern in Figure 4 (top trace) to L-glufosinate ammonium monohydrate, which is consistent with "Form A" in Figure 4 (bottom trace) that was crystallized and isolated in a previous study.

[0116] Example 3. Antisolvent:solvent ratio studies Antisolvent:solvent ratio studies were conducted using a material containing 76.4% (w / w) total glufosinate ammonium and having an L-glufosinate:D-glufosinate (L:D) ratio of 81:19. A fluid mixture containing methanol, water, and approximately 0.4 M ammonium hydroxide was used, as shown in Table 4.

[0117] [Table 4]

[0118] Crystals with enriched L:D-glufosinate ratios were obtained from single direct crystallizations in all solvent systems. L:D-glufosinate ratios >99:1 were obtained in solvent systems of 50:50 to 70:30 methanol:water. Crystal purity of >90% as L-glufosinate ammonium hydrate was also obtained in solvent systems of 50:50 to 70:30 methanol:water.

[0119] Example 4. Eutectic determination Crystallization studies of L-glufosinate ammonium lots with total glufosinate ammonium purity between 75-80% and L:D-glufosinate ratios between 72:28 and 81:19, as shown in Tables 5 and 6, were conducted for 16 hours at 30°C. The methanol to water ratio for these experiments was 50:50 (v:v). Samples were taken after 6 hours of mixing at room temperature (Table 5) and again after 12 days of mixing at room temperature (Table 6). Lots 17, 18, 19, 20, and 21 produced L-glufosinate ammonium hydrate crystals substantially enriched in L-glufosinate after the 6 hour mixing period (Table 5). No crystals were observed in Lots 13 and 15 after the 6 hour period, but longer mixing times resulted in crystal formation in these lots (Table 6). However, Lots 13 and 15 contained initial ratios of L-glufosinate to D-glufosinate of 72:28 and 76:24, respectively, and the crystals obtained from these two lots were not enriched in the L-glufosinate isomer (Table 6). Other lots processed by this procedure yielded crystals with L:D ratios substantially higher than 50:50 (Table 6). Comparison of the results obtained from Lots 16 and 20 indicates a eutectic point of approximately L:D-glufosinate ratio of about 76:24.

[0120] [Table 5]

[0121] [Table 6]

[0122] Example 5. 20 gram scale crystallization process L-glufosinate ammonium starting material (20 g; 76.4% total glufosinate ammonium, 81:19 L:D-glufosinate ammonium ratio) was added to 12.5 mL of a 50:50 (v:v) water:methanol solution with 0.36 M ammonium hydroxide at room temperature with stirring. The temperature was raised to 45° C. with sonication to dissolve the solids, and the solution was then placed in a shaker at 30° C. After 1 h, 0.2 wt % starting material (g / g) of L-glufosinate ammonium monohydrate seed crystals (>70 wt % L-glufosinate ammonium purity, >97:3 L:D-glufosinate ratio) were added. The slurry was stirred at 30° C. for 16 h for crystallization. The precipitated crystals were centrifuged, washed with methanol, filtered, and dried to give 7.8 g of purified L-glufosinate ammonium monohydrate crystals: L-glufosinate ammonium monohydrate purity 89.8% by weight; L:D-glufosinate ratio 98.5:1.5; recovery of L-glufosinate ammonium from the starting material 54.5%.

[0123] Example 6. 100 gram scale crystallization process L-glufosinate ammonium starting material (100 g; 76.4% total glufosinate ammonium, 81:19 L:D-glufosinate ammonium ratio) was added to 62 mL of a 40:60 (v:v) water:methanol solution with 0.36 M ammonium hydroxide at room temperature with stirring. The temperature was raised to 50° C. with stirring to dissolve the solids, then the solution was held at 50° C. for 1 hour, after which 100 mg of L-glufosinate ammonium monohydrate seed crystals (>70% L-glufosinate purity by weight, >97:3 L:D-glufosinate ratio) in a slurry with 10 mL methanol was added. After seeding, the solution was held at 50° C. for 20 minutes, then the temperature was cooled to 45° C. and held for 1 hour. After 1 hour, the temperature was reduced to 40° C. with a 1 hour hold, after which the temperature was reduced to 30° C. and allowed to crystallize overnight. The slurry was stirred for 16 hours at 30° C. to allow crystallization. After 30 minutes at room temperature, the precipitated crystals were centrifuged, washed with methanol, filtered, and dried to give 53.2 g of purified L-glufosinate ammonium monohydrate crystals: 86.5% wt L-glufosinate ammonium monohydrate purity; 96.2:3.8 L:D-glufosinate ratio; 68.6% recovery of L-glufosinate ammonium from starting material.

[0124] Example 7. 2 Kilogram Scale Crystallization Process L-glufosinate ammonium starting material (2000 g; 76.4% total glufosinate ammonium, 81:19 L:D-glufosinate ammonium ratio) was added to 1140 g of 48:52 methanol:water (0.4M NH4OH) with stirring at room temperature. The slurry was transferred to a 5 L jacketed crystallization vessel. The temperature was raised to 50°C to dissolve the solids (stirred at 400 rpm) and then held at 50°C for 1 hour, after which 40 g of L-glufosinate ammonium seed crystals (>70% L-glufosinate ammonium purity by weight, >97:3 L:D-glufosinate ratio) as 2% by weight starting material (g / g) was added as a slurry in 40 mL of methanol. After seed addition, stirring was reduced to 250 rpm. After 30 minutes, the temperature was reduced to 45°C. The batch temperature was reduced by 5°C after each 30-minute temperature hold until the temperature was 35°C. After 30 minutes at 35°C, the agitation was reduced to 200 rpm, the temperature was cooled to room temperature, and allowed to crystallize overnight (14-18 hours). The precipitated crystals were centrifuged, washed with methanol, filtered, and dried to yield 1,071 g of purified L-glufosinate ammonium monohydrate crystals: L-glufosinate ammonium monohydrate purity 84.1 wt%; L:D-glufosinate ratio 96.4:3.6; and 65.8% recovery of L-glufosinate ammonium from the starting material.

[0125] Example 8. Recrystallization treatment L-glufosinate ammonium starting material (82.4 g; 76.4% total glufosinate ammonium, 97.8:2.2 L:D-glufosinate ammonium ratio) was added to 35.4 g of a 70:30 (v:v) water:methanol solution with stirring at room temperature. The temperature was raised to 60° C. with stirring to dissolve the solids. After heating at 60° C. for approximately 1 hour, 160 mL of methanol was added with stirring to crash out the inorganic salts. The resulting slurry was centrifuged to pellet the inorganic salts as solid precipitants, and the mother liquor was decanted and allowed to crystallize at room temperature for 16 hours. The crystals were filtered, washed with methanol, and dried to give 46.5 g of purified L-glufosinate ammonium monohydrate crystals: L-glufosinate ammonium monohydrate purity 99.2% by weight; L:D-glufosinate ratio 99.2:0.8; recovery of L-glufosinate ammonium from the starting material 68.6%.

[0126] Example 9: Crystallization of L-glufosinate ammonium monohydrate with the addition of an ammonia source The L-glufosinate ammonium starting material (50 g, 77% total L-glufosinate ammonium, 7.3% ammonium glutamate) was added to 36.7 g of a 45:55 (w:w) methanol:water solution with a total concentration of 0.4 M ammonium hydroxide with stirring at room temperature. The temperature was raised to 50° C. with sonication to dissolve the solids. The solution was transferred to a glass round-bottom flask with overhead stirring and mixed at 250 rpm for 1 hour with the temperature maintained at 50° C. throughout the entire mixing period. One gram of L-glufosinate ammonium monohydrate form B seed crystals (>90% by weight L-glufosinate ammonium purity) was added to the batch as a slurry in 3 mL of methanol. After 30 minutes, the temperature was reduced to 45° C. The batch temperature was further reduced by 5° C. after each 30 minute hold period until the temperature was 30° C. Three milliliters of methanol was added and the slurry was stirred at 30° C. for 16 hours. After 30 minutes at room temperature, the slurry was diluted with 25 mL of methanol and filtered. The crystals were washed with methanol and dried to give 20.7 g of L-glufosinate ammonium monohydrate crystals (93.3% L-glufosinate ammonium monohydrate purity, 45.5% recovery from starting material, <1% D-glufosinate ammonium, and 0.58% ammonium glutamate). The crystals were analyzed by X-ray powder diffraction and the resulting pattern was consistent with that of L-glufosinate ammonium monohydrate form B. The solid was measured for particle size and D v 90 turned out to be 70.7 microns.

[0127] Example 10: Crystallization of L-glufosinate ammonium monohydrate without the addition of an ammonia source L-glufosinate ammonium starting material (50 g, 77% total L-glufosinate ammonium, 7.3% ammonium glutamate) was added to 35.0 g of 45:55 (w:w) methanol:water. No ammonium hydroxide was added. The temperature was raised to 50° C. with sonication to dissolve the solids. The solution was transferred to a glass round-bottom flask with overhead stirring and mixed at 250 rpm for 1 hour while maintaining the temperature at 50° C. throughout the entire mixing period. One gram of L-glufosinate ammonium monohydrate form B seed crystals (>90% by weight L-glufosinate ammonium purity) was added to the batch as a slurry in 3 mL of methanol. After 30 minutes, the temperature was reduced to 45° C. The batch temperature was further reduced by 5° C. after each 30 minute hold period until the temperature was 30° C. Three milliliters of methanol was added and the slurry was stirred at 30° C. for 16 hours. After 30 minutes at room temperature, the slurry was diluted with 25 mL of methanol and filtered. The crystals were washed with methanol and dried to give 12.5 g of L-glufosinate ammonium monohydrate crystals (97.0% L-glufosinate ammonium monohydrate purity, 28.7% recovery from starting material, <1% D-glufosinate ammonium and 0.69% ammonium glutamate). The crystals were analyzed by X-ray powder diffraction and the resulting pattern was consistent with that of L-glufosinate ammonium monohydrate form B, although some peaks consistent with L-glufosinate ammonium monohydrate form A were present. The solids were measured for particle size and found to be 1.0 g. v 90 turned out to be 102 microns.

[0128] Example 11: Crystallization of L-glufosinate ammonium monohydrate with the addition of racemic glufosinate L-glufosinate ammonium starting material (37.5 g, 72.4% total L-glufosinate ammonium, 11.4% ammonium glutamate) and racemic glufosinate ammonium (12.5 g, 95% total glufosinate ammonium) were added to 30.5 g of a 50:50 (w:w) methanol:water solution with a total concentration of 0.4 M ammonium hydroxide at room temperature with stirring. The temperature was raised to 50° C. with sonication to dissolve the solids. The solution was placed in a glass round bottom flask with overhead stirring and mixed at 250 rpm for 1 hour while maintaining the temperature at 50° C. throughout the entire mixing period. One gram of L-glufosinate ammonium monohydrate form B seed crystals (>90% by weight L-glufosinate ammonium purity) was added as a slurry in 3 mL of methanol. After 30 minutes, the temperature was reduced to 45° C. The batch temperature was further reduced by 5° C. after each 30 minute hold period until the temperature was 30° C. Three milliliters of methanol was added and the slurry was stirred at 30° C. for 16 hours. After 30 minutes at room temperature, the slurry was diluted with 25 mL of methanol and filtered. The crystals were washed with methanol and dried to give 20.6 g of L-glufosinate ammonium monohydrate crystals (94.4% L-glufosinate ammonium monohydrate purity, 51.8% recovery from starting material, containing <1% D-glufosinate ammonium and 0.7% D-glufosinate ammonium monohydrate, 1.53% ammonium glutamate).

[0129] Example 12: Preparation of crystalline L-glufosinate Crystallization of L-glutamic acid A solution containing L-glufosinate and L-glutamic acid, prepared as described in Example 1 of WO 2019 / 018406, is charged to the reactor and agitation is commenced. Concentrated sulfuric acid is charged to the reactor until the batch reaches a pH of 5.0-6.0; the batch is cooled as necessary and the temperature is maintained at 20-40°C during the addition of sulfuric acid. After complete addition of sulfuric acid, seed crystals of L-glutamic acid are added to the batch to promote crystal growth. While mixing the seed crystals in the batch, concentrated sulfuric acid is added to the batch until the batch reaches a pH of 3.5-3.9, after which the batch is cooled to 0-5°C and held at this temperature for at least 15 minutes. After the holding period, the batch is filtered to remove the L-glutamic acid crystals. The filtrate is concentrated under vacuum at a maximum jacket temperature of 70°C until the total dissolved solids are 28% by weight or greater.

[0130] Chromatography The concentrated filtrate was fed to a chromatography system followed by a water eluent. Chromatography can be operated in either batch or simulated moving bed (SMB) mode. The chromatography column is packed with hydroxylated polyacrylate or hydroxylated polymethacrylate resin. Separation occurs as a pulse of feed passes through the resin and partially purified L-glufosinate ammonium is collected from the pulse tip downstream of the feed location. After the product is collected, the water feed is continued to prepare the resin for the subsequent feed of the concentrated filtrate.

[0131] Desalination The fraction containing the partially purified L-glufosinate solution is charged to the reactor and agitation is initiated. The pH of the solution is adjusted to pH 6-7 using ammonium hydroxide. The batch is concentrated under vacuum until the total dissolved solids concentration is at least 48-50% by weight. The maximum jacket temperature for the concentration step is 70 °C. After concentration, the batch is cooled to 10-15 °C, during which time the ammonium sulfate crystallizes. The batch is mixed at 4-10 °C for at least 30 minutes and then filtered to remove the ammonium sulfate crystals. The ammonium sulfate cake is washed with methanol, but the methanol wash is not immediately combined with the filtrate.

[0132] The aqueous filtrate is charged to the reactor and agitation is commenced. Optionally, previously isolated ammonium sulfate crystals can be added to the batch to act as seed crystals. A portion of methanol is added to the reactor, then the batch is cooled to 10-15°C. The methanol cake wash is added as part of the first methanol charge. A second portion of methanol is added to the reactor. The batch is stirred at 4-10°C for at least 30 minutes, then the batch is filtered to remove the ammonium sulfate crystals. The ammonium sulfate cake is washed with methanol and the wash filtrate is combined with the batch.

[0133] Preparation of starting materials for crystallization The desalted filtrate is charged to a reactor and concentrated under vacuum until the total dissolved solids concentration is about 48% by weight. The maximum jacket temperature during the concentration step is 70° C. The concentrated solution is transferred to a vacuum dryer where the batch is concentrated under vacuum to produce solids with less than 5% total moisture.

[0134] Crystallization The solid material is charged to a reactor and combined with methanol and aqueous ammonium hydroxide. The slurry is heated to 50-55°C with mixing and held until the solids are dissolved. A slurry consisting of L-glufosinate ammonium monohydrate form B seed crystals and methanol is charged to the reactor. After 30 minutes of mixing, the batch temperature is reduced from 50°C to 45°C. The temperature is reduced in 5°C increments followed by a 30 minute mixing period until the batch temperature reaches 30°C. A small amount of methanol is added and the batch is then mixed at 30°C for at least 12 hours. After this mixing period, the batch is cooled to 20-25°C and methanol is added to the batch. After 30 minutes of mixing, the batch is filtered. The filter cake is washed with methanol and the resulting filter cake is dried under heat and vacuum to obtain L-glufosinate ammonium monohydrate form B crystals.

[0135] Example 13: Improved variant DAAO enzymes for carrying out enzymatic reactions DAAO Array The coding sequence of the mutant DAAO from Rhodosporidium toruloides (e.g., consisting of the MGSSHHHHHHSSGLVPRGSHMMARIRL (SEQ ID NO: 4) leader sequence and the F58K and M213S mutations) was cloned into a pET14b vector to allow expression of an N-terminal 6xHis-tagged protein. The pET14b-RgDAAO plasmid was transformed into BL21(BE3)trxB pLysS cells. The sequence of the wild-type DAAO from Rhodosporidium toruloides (to which the numbering described for the first four entries in Table 7 corresponds (Ac302, Mut5, Mut7 (SEQ ID NO: 3), and Mut18)) is shown in SEQ ID NO: 1. The sequence of the fifth entry in Table 7, Mut846, is provided in SEQ ID NO: 2. SEQ ID NO:5 represents the Mut7 sequence with the linker SEQ ID NO:4.

[0136] Stock solution: The following dye stock solutions were prepared: 2,4,6-tribromo-3-hydroxybenzoic acid (TBHBA) at 20 mg / mL stock solution in DMSO; and 4-aminoantipyrine (4-AAP) at 100 mg / mL stock solution in water. The following enzyme stock solutions were prepared: 1 mg / mL stock solution of horseradish peroxide (HRP) form 6 in potassium phosphate buffer at pH 8.0. The following substrate stock solutions were prepared: various concentrations of racemic glufosinate in potassium phosphate buffer at pH 8.0, such that the initial reaction concentrations of racemic glufosinate were 0, 1, 10, 100, 250, and 500 nM. The DAAO enzyme was produced in E. coli, dissolved, and the cell-free extract was lyophilized. The amount of enzyme in the cell-free extract was quantified using SDS-PAGE and stained with Coomassie blue.

[0137] Reaction mixture: The following reaction mixture was prepared: Mix A is a combination of the substrate and the HRP enzyme. Solutions were prepared in reaction buffer for each substrate concentration to be assayed. These solutions were twice the final substrate concentration, which was 0.2 mg / mL for the HRP solution.

[0138] Mix B is the dye mixture. To 5 mL of reaction buffer, 120 μL of TBHBA solution and 400 μL of 4-AAP solution were added.

[0139] Mix C is the enzyme mixture. A 0.02 mg / mL solution of DAAO in reaction buffer was prepared. The final DAAO concentration in the reaction was 5 μg / mL.

[0140] protocol: A spectrophotometer was used at a wavelength of 460 nm. The temperature for carrying out the assay was 30° C. The measurements were taken for 15 minutes. A 96-well plate was used and the following mixes (with duplicates) were added using multichannel in the following order: 100 μl Mix A, 50 μl Mix B, and 50 μl Mix C.

[0141] Enzyme kinetics were measured as described above and plotted on a Michaelis-Menten graph, which was used to calculate Vmax. The mutant DAAO enzymes exhibited a wide range of activity, as shown in Table 7 below:

[0142] [Table 7]

[0143] array

[0144] SEQ ID NO:1: TIFF2025041627000009.tif51169

[0145] SEQ ID NO:2: TIFF2025041627000010.tif51169

[0146] SEQ ID NO:3: TIFF2025041627000011.tif51169

[0147] SEQ ID NO:4: TIFF2025041627000012.tif8163

[0148] SEQ ID NO:5: TIFF2025041627000013.tif51169

[0149] It is understood that the terminology used herein is for the purpose of describing particular embodiments only, and that this terminology is not intended to be limiting. The scope of the present invention will be limited only by the appended claims. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Where a range of values ​​is provided, it is understood that each intervening value between the upper and lower limits of this range, and any other stated value or intervening value within the stated range, to the tenth of the unit of the lower limit, is encompassed in the present invention, unless the context clearly dictates otherwise. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges or may also be encompassed in the present invention, subject to any specifically excluded limit in the stated range. Where a stated range includes one or both of the above limits, ranges excluding either or both of these included limits are also included in the present invention. Certain ranges are presented herein with numerical values ​​preceded by the term "about" or the term "around". The terms "about" and "around" are used herein to provide literature support for the exact number it precedes, as well as for a number that is close to or approximately the number it precedes. When determining whether a number is close to or approximately a number specifically mentioned, the close or approximate unmentioned number may be a number that provides a substantial equivalent to the specifically mentioned number in the context in which it is indicated. When "X" is a value modified by "about" or "around", "about X" or "around X" may generally indicate a value of 0.95X to 1.05X, such as 0.98X to 1.02X or 0.99X to 1.01X. Any reference to "about X" or "around X" specifically refers to at least the values ​​X, 0.95X, 0.96X, 0.97X, 0.98X, 0.99X, 1.01X, 1.02X, 1.03X, 1.04X, and 1.05X.Thus, "about X" and "around X" are intended to teach and provide written recitation support for the limitations of the claims, e.g., "0.98X."

[0150] All publications, patents, and patent applications cited herein are incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference. Furthermore, each cited publication, patent, and patent application is incorporated by reference herein to disclose and describe the subject matter in connection with which the publication is cited. The citation of any publication is for its disclosure prior to the filing date and should not be construed as an admission that the inventions described herein are not entitled to antedate such publication by virtue of prior invention. Further, the dates of publications provided may be different from the actual publication dates, which may need to be independently confirmed.

[0151] It should be noted that the claims may be written to exclude any optional element. This statement is therefore intended to serve as a predicate for the use of exclusive language such as "solely," "only," and the like, or the use of a "negative" limitation in connection with the recitation of claim elements. As will be apparent to one of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has separate components and features that may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the invention. Any recited method may be carried out in the order of events recited or in any other order that is logically possible. Any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention, and representative exemplary methods and materials are described herein.

[0152] Sequence Listing SEQUENCE LISTING <110> BASF SE <120> METHODS FOR PRODUCING CRYSTALLINE L-GLUFOSINATE AMMONIUM MONOHYDRATE <130> PA24-594 <150> US 62 / 834,675 <151> 2019-04-16 <150> US 62 / 978,005 <151> 2020-02-18 <160> 5 <170> PatentIn version 3.5 <210> 1 <211> 368 <212> PRT <213> Rhodosporidium toruloides <400> 1 Met His Ser Gln Lys Arg Val Val Val Leu Gly Ser Gly Val Ile Gly 1 5 10 15 Leu Ser Ser Ala Leu Ile Leu Ala Arg Lys Gly Tyr Ser Val His Ile 20 25 30 Leu Ala Arg Asp Leu Pro Glu Asp Val Ser Ser Gln Thr Phe Ala Ser 35 40 45 Pro Trp Ala Gly Ala Asn Trp Thr Pro Phe Met Thr Leu Thr Asp Gly 50 55 60 Pro Arg Gln Ala Lys Trp Glu Glu Ser Thr Phe Lys Lys Trp Val Glu 65 70 75 80 Leu Val Pro Thr Gly His Ala Met Trp Leu Lys Gly Thr Arg Arg Phe 85 90 95 Ala Gln Asn Glu Asp Gly Leu Leu Gly His Trp Tyr Lys Asp Ile Thr 100 105 110 Pro Asn Tyr Arg Pro Leu Pro Ser Ser Glu Cys Pro Pro Gly Ala Ile 115 120 125 Gly Val Thr Tyr Asp Thr Leu Ser Val His Ala Pro Lys Tyr Cys Gln 130 135 140 Tyr Leu Ala Arg Glu Leu Gln Lys Leu Gly Ala Thr Phe Glu Arg Arg 145 150 155 160 Thr Val Thr Ser Leu Glu Gln Ala Phe Asp Gly Ala Asp Leu Val Val 165 170 175 Asn Ala Thr Gly Leu Gly Ala Lys Ser Ile Ala Gly Ile Asp Asp Gln 180 185 190 Ala Ala Glu Pro Ile Arg Gly Gln Thr Val Leu Val Lys Ser Pro Cys 195 200 205 Lys Arg Cys Thr Met Asp Ser Ser Asp Pro Ala Ser Pro Ala Tyr Ile 210 215 220 Ile Pro Arg Pro Gly Gly Glu Val Ile Cys Gly Gly Thr Tyr Gly Val 225 230 235 240 Gly Asp Trp Asp Leu Ser Val Asn Pro Glu Thr Val Gln Arg Ile Leu 245 250 255 Lys His Cys Leu Arg Leu Asp Pro Thr Ile Ser Ser Asp Gly Thr Ile 260 265 270 Glu Gly Ile Glu Val Leu Arg His Asn Val Gly Leu Arg Pro Ala Arg 275 280 285 Arg Gly Gly Pro Arg Val Glu Ala Glu Arg Ile Val Leu Pro Leu Asp 290 295 300 Arg Thr Lys Ser Pro Leu Ser Leu Gly Arg Gly Ser Ala Arg Ala Ala 305 310 315 320 Lys Glu Lys Glu Val Thr Leu Val His Ala Tyr Gly Phe Ser Ser Ala 325 330 335 Gly Tyr Gln Gln Ser Trp Gly Ala Ala Glu Asp Val Ala Gln Leu Val 340 345 350 Asp Glu Ala Phe Gln Arg Tyr His Gly Ala Ala Arg Glu Ser Lys Leu 355 360 365 <210> 2 <211> 375 <212> PRT <213> Rhodosporidium toruloides <400> 2 Met Ala Ser Pro Ser Asn Lys Gln Ile Val Val Leu Gly Ala Gly Val 1 5 10 15 Ile Gly Leu Thr Thr Ala Val Lys Ile Gln Glu Gln Arg Gly Tyr Gln 20 25 30 Val Thr Ile Ile Ala Glu Ile Leu Pro Ser Asp Pro Lys Ser Ile Arg 35 40 45 Tyr Thr Ser His Trp Ala Gly Ala His His Val Ser Leu Ala Gly Glu 50 55 60 Asp Lys Leu Gln Ala Arg Val Asp Gln Glu Thr Phe Gly Val Met Trp 65 70 75 80 Glu Met Ser Ala Pro Gly Gly Glu Ala Glu Gly Cys Phe Leu Arg Gln 85 90 95 Lys Gln Val Glu Tyr Tyr Cys Asp Lys Gln Ala Asp Pro His Pro Leu 100 105 110 Glu His Met Pro Asp Phe Arg Arg Leu Asp Glu Asn Ser Leu Ile Pro 115 120 125 Asn Thr Val Ala Gly Ile Gly Phe Thr Thr Leu Thr Ile Asp Thr Pro 130 135 140 Ile Tyr Leu Asn Tyr Leu Leu Ser Arg Phe Leu Ala Arg Gly Gly Ala 145 150 155 160 Ile Val Arg Gly Ser Val Gln His Ile Ser Gln Val Val Asp Gly Gly 165 170 175 Ala Arg Val Phe Thr Gly Ser Lys Ser Ala Gly Val Pro Val Asp Ala 180 185 190 Val Ile Val Cys Ala Gly Ile Gly Ala Arg Phe Leu Gly Gly Val Glu 195 200 205 Asp Lys Asp Val Tyr Pro Ile Arg Gly Gln Thr Val Leu Leu Arg Ala 210 215 220 Pro Trp Ile Arg Phe Gly Arg Thr Met Ser Ser Lys Asp Gly Leu Tyr 225 230 235 240 Thr Tyr Ile Ile Pro Arg Arg Ser Gly Asp Val Ile Val Gly Gly Ile 245 250 255 Lys Val Pro Asn Asp Trp Tyr Pro Thr Pro Arg Pro Glu Thr Thr Gln 260 265 270 Asp Ile Leu Lys Arg Gly Leu Ala Leu Cys Pro Glu Leu Ala Pro Gln 275 280 285 Ser Ile Arg Asp Gln Arg Glu Pro Thr Val Asp Asp Leu Arg Pro Leu 290 295 300 Val Ile Glu Glu Gly Cys Gly Leu Arg Pro Gly Arg Lys Gly Gly Ile 305 310 315 320 Arg Leu Glu Val Glu Trp Tyr Ala Lys Thr Asp Gly Gln Ala Pro Lys 325 330 335 Val Pro Ile Val His Asn Tyr Gly His Gly Gly Ala Gly Phe Gln Ala 340 345 350 Ser Trp Gly Ser Ala Ser Val Ala Leu Glu Leu Leu Glu Lys Ala Leu 355 360 365 Ala Gln Ala Arg Leu Ala Met 370 375 <210> 3 <211> 368 <212> PRT <213> Rhodosporidium toruloides <400> 3 Met His Ser Gln Lys Arg Val Val Val Leu Gly Ser Gly Val Ile Gly 1 5 10 15 Leu Ser Ser Ala Leu Ile Leu Ala Arg Lys Gly Tyr Ser Val His Ile 20 25 30 Leu Ala Arg Asp Leu Pro Glu Asp Val Ser Ser Gln Thr Phe Ala Ser 35 40 45 Pro Trp Ala Gly Ala Val Trp Asn Pro His Met Thr Leu Thr Asp Gly 50 55 60 Pro Arg Gln Ala Lys Trp Glu Glu Ser Thr Phe Lys Lys Trp Val Glu 65 70 75 80 Leu Val Pro Thr Gly His Ala Met Trp Leu Lys Gly Thr Arg Arg Phe 85 90 95 Ala Gln Asn Glu Asp Gly Leu Leu Gly His Trp Tyr Lys Asp Ile Thr 100 105 110 Pro Asn Tyr Arg Pro Leu Pro Ser Ser Glu Cys Pro Pro Gly Ala Ile 115 120 125 Gly Val Thr Tyr Asp Thr Leu Ser Val His Ala Pro Lys Tyr Cys Gln 130 135 140 Tyr Leu Ala Arg Glu Leu Gln Lys Leu Gly Ala Thr Phe Glu Arg Arg 145 150 155 160 Thr Val Thr Ser Leu Glu Gln Ala Phe Asp Gly Ala Asp Leu Val Val 165 170 175 Asn Ala Thr Gly Leu Gly Ala Lys Ser Ile Ala Gly Ile Asp Asp Gln 180 185 190 Ala Ala Glu Pro Ile Arg Gly Gln Thr Val Leu Val Lys Ser Pro Cys 195 200 205 Lys Arg Cys Thr Ser Asp Ser Ser Asp Pro Ala Ser Pro Ala Tyr Ile 210 215 220 Ile Pro Arg Pro Gly Gly Glu Val Ile Cys Gly Gly Thr Tyr Gly Val 225 230 235 240 Gly Asp Trp Asp Leu Ser Val Asn Pro Glu Thr Val Gln Arg Ile Leu 245 250 255 Lys His Cys Leu Arg Leu Asp Pro Thr Ile Ser Ser Asp Gly Thr Ile 260 265 270 Glu Gly Ile Glu Val Leu Arg His Asn Val Gly Leu Arg Pro Ala Arg 275 280 285 Arg Gly Gly Pro Arg Val Glu Ala Glu Arg Ile Val Leu Pro Leu Asp 290 295 300 Arg Thr Lys Ser Pro Leu Ser Leu Gly Arg Gly Ser Ala Arg Ala Ala 305 310 315 320 Lys Glu Lys Glu Val Thr Leu Val His Ala Tyr Gly Phe Ser Ser Ala 325 330 335 Gly Tyr Gln Gln Ser Trp Gly Ala Ala Glu Asp Val Ala Gln Leu Val 340 345 350 Asp Glu Ala Phe Gln Arg Tyr His Gly Ala Ala Arg Glu Ser Lys Leu 355 360 365 <210> 4 <211> 27 <212> PRT <213> Rhodosporidium toruloides <400> 4 Met Gly Ser Ser His His His His His His Ser Ser Gly Leu Val Pro 1 5 10 15 Arg Gly Ser His Met Met Ala Arg Ile Arg Leu 20 25 <210> 5 <211> 395 <212> PRT <213> Rhodosporidium toruloides <400> 5 Met Gly Ser Ser His His His His His His Ser Ser Gly Leu Val Pro 1 5 10 15 Arg Gly Ser His Met Met Ala Arg Ile Arg Leu Met His Ser Gln Lys 20 25 30 Arg Val Val Val Leu Gly Ser Gly Val Ile Gly Leu Ser Ser Ala Leu 35 40 45 Ile Leu Ala Arg Lys Gly Tyr Ser Val His Ile Leu Ala Arg Asp Leu 50 55 60 Pro Glu Asp Val Ser Ser Gln Thr Phe Ala Ser Pro Trp Ala Gly Ala 65 70 75 80 Val Trp Asn Pro His Met Thr Leu Thr Asp Gly Pro Arg Gln Ala Lys 85 90 95 Trp Glu Glu Ser Thr Phe Lys Lys Trp Val Glu Leu Val Pro Thr Gly 100 105 110 His Ala Met Trp Leu Lys Gly Thr Arg Arg Phe Ala Gln Asn Glu Asp 115 120 125 Gly Leu Leu Gly His Trp Tyr Lys Asp Ile Thr Pro Asn Tyr Arg Pro 130 135 140 Leu Pro Ser Ser Glu Cys Pro Pro Gly Ala Ile Gly Val Thr Tyr Asp 145 150 155 160 Thr Leu Ser Val His Ala Pro Lys Tyr Cys Gln Tyr Leu Ala Arg Glu 165 170 175 Leu Gln Lys Leu Gly Ala Thr Phe Glu Arg Arg Thr Val Thr Ser Leu 180 185 190 Glu Gln Ala Phe Asp Gly Ala Asp Leu Val Val Asn Ala Thr Gly Leu 195 200 205 Gly Ala Lys Ser Ile Ala Gly Ile Asp Asp Gln Ala Ala Glu Pro Ile 210 215 220 Arg Gly Gln Thr Val Leu Val Lys Ser Pro Cys Lys Arg Cys Thr Ser 225 230 235 240 Asp Ser Ser Asp Pro Ala Ser Pro Ala Tyr Ile Ile Pro Arg Pro Gly 245 250 255 Gly Glu Val Ile Cys Gly Gly Thr Tyr Gly Val Gly Asp Trp Asp Leu 260 265 270 Ser Val Asn Pro Glu Thr Val Gln Arg Ile Leu Lys His Cys Leu Arg 275 280 285 Leu Asp Pro Thr Ile Ser Ser Asp Gly Thr Ile Glu Gly Ile Glu Val 290 295 300 Leu Arg His Asn Val Gly Leu Arg Pro Ala Arg Arg Gly Gly Pro Arg 305 310 315 320 Val Glu Ala Glu Arg Ile Val Leu Pro Leu Asp Arg Thr Lys Ser Pro 325 330 335 Leu Ser Leu Gly Arg Gly Ser Ala Arg Ala Ala Lys Glu Lys Glu Val 340 345 350 Thr Leu Val His Ala Tyr Gly Phe Ser Ser Ala Gly Tyr Gln Gln Ser 355 360 365 Trp Gly Ala Ala Glu Asp Val Ala Gln Leu Val Asp Glu Ala Phe Gln 370 375 380 Arg Tyr His Gly Ala Ala Arg Glu Ser Lys Leu 385 390 395

Claims

1. 1. A method for preparing crystalline L-glufosinate ammonium monohydrate, the method comprising the steps of: (i) forming a mixture comprising an L-glufosinate starting material and an aqueous solution, wherein the glufosinate starting material comprises L-glufosinate ammonium and D-glufosinate ammonium; The aqueous solution comprises water and a water-miscible organic solvent. the steps; (ii) crystallizing L-glufosinate ammonium from the mixture of step (i) to form L-glufosinate ammonium monohydrate crystals; and (iii) after step (ii), separating at least a portion of the L-glufosinate ammonium monohydrate crystals from the aqueous solution. Including, This results in the preparation of crystalline L-glufosinate ammonium monohydrate. wherein the crystalline L-glufosinate ammonium monohydrate comprises L-glufosinate ammonium monohydrate Form B, the water-miscible organic solvent is methanol, and the ratio of the water-miscible organic solvent to water in the aqueous solution is 30:70 to 75:25 by volume; L-glufosinate ammonium monohydrate form B showed the following average molecular weights as measured by a diffractometer using Cu-Kα radiation: 10.0, 11.4, 12.5, 16.5, 17.4, 18.1, 19.6, 20.0, 21.8, 22.9, 23.6, 24.0, 25.1, 25.5, 26.1, 26.3, 26.4, 27.9, 28.2, 28.4, 28. 7, 29.2, 30.2, 30.9, 31.6, 31.7, 32.7, 33.0, 33.3, 34.3, 35.2, 36.7, 37.2, 37.4, 37.8, 38.3, 38.7, and 39.3 °2θ, ±0.2 °2θ, The method.

2. The method of claim 1 , wherein the aqueous solution further comprises a source of ammonia.

3. 3. The method of claim 2, wherein the ammonia source is ammonium hydroxide.

4. 2. The method of claim 1, wherein the molar ratio of L-glufosinate ammonium to D-glufosinate ammonium in the glufosinate starting material is at least 70:

30.

5. The method of any one of claims 1 to 4, wherein the molar ratio of L-glufosinate ammonium to D-glufosinate ammonium in the L-glufosinate starting material is at least 76:

24.

6. 6. The method of any one of claims 1 to 5, wherein the L-glufosinate starting material further comprises one or more components selected from the group consisting of L-glutamic acid and its salts, D-glutamic acid and its salts, L-pyroglutamic acid and its salts, 2-oxoglutaric acid and its salts, succinic acid and its salts, 2-oxo-4-(hydroxy(methyl)phosphinoyl)butyric acid and its salts, sodium sulfate, ammonium sulfate, sodium chloride, ammonium chloride, monosodium phosphate, disodium phosphate, monoammonium phosphate, and diammonium phosphate.

7. 7. The method of claim 6, wherein the L-glufosinate starting material comprises L-glutamic acid.

8. The method according to any one of claims 1 to 7, wherein the amount of glufosinate in the L-glufosinate starting material is from 70% (w / w) to 90% (w / w).

9. 9. The method of claim 8, wherein the amount of glufosinate in the L-glufosinate starting material is 75% (w / w) to 85% (w / w).

10. 10. The method according to claim 1, wherein the concentration of ammonium hydroxide in the aqueous solution is from 0.1M to 1M.

11. 11. The method of claim 10, wherein the concentration of ammonium hydroxide in the aqueous solution is 0.4M.

12. The method of any one of claims 1 to 11, wherein the ratio of L-glufosinate starting material to aqueous solution in step (i) is from 0.5:1 to 5:1 by weight.

13. 13. The method of claim 12, wherein the ratio of L-glufosinate starting material to aqueous solution in step (i) is from 1:1 to 2:1 by weight.

14. 14. The method of any one of claims 1 to 13, wherein step (ii) comprises heating the mixture of step (i) to form a heated mixture.

15. 15. The method of claim 14, wherein the mixture of step (i) is heated to at least 45°C.

16. 16. The method of claim 13 or claim 15, wherein the heated mixture is maintained at a temperature of at least 45°C for a period of from 10 minutes to 6 hours prior to step (iii).

17. The method of any one of claims 14 to 16, further comprising, prior to step (iii), cooling the heated mixture to form a cooled mixture.

18. 18. The method of claim 17, wherein the heated mixture is cooled to a temperature of 30° C. or less.

19. 19. The method of any one of claims 1 to 18, wherein separating at least a portion of the L-glufosinate crystals in step (iii) comprises filtering the mixture of step (ii), centrifuging the mixture of step (ii), or a combination thereof.

20. The method of any one of claims 1 to 19, further comprising one or more of the following steps: step (iv) washing the L-glufosinate ammonium monohydrate crystals; and step (v) drying the L-glufosinate ammonium monohydrate crystals.

21. The method of any one of claims 1 to 20, wherein the crystalline L-glufosinate ammonium monohydrate further comprises D-glufosinate.

22. 22. The method of claim 21, wherein the molar ratio of L-glufosinate to D-glufosinate is at least 90:

10.

23. 23. The method of claim 21 or 22, wherein the molar ratio of L-glufosinate to D-glufosinate is at least 95:

5.

24. L-glufosinate ammonium monohydrate form B has the following average molecular weights: 10.0, 11.4, 12.5, 16.5, 17.4, 18.1, 19.6, 20.0, 21.8, 22.9, 23.6, 24.0, 25.1, 25.5, 26.1, 26.3, 26.4, 27.9, 28.2, 28.4, 28.7, 29.2, 30.2, 30.9, 31.6, 31.7, 32.7, 33.0, 33.3, 34.3, 35.2, 36.7, 37.2, 37.4, 37.8, 38.3, 38.7, and 39.3 °2θ, ±0.2 24. The method according to any one of claims 1 to 23, characterized by an X-ray powder diffraction (XRPD) pattern comprising at least six peaks selected from °2θ.

25. 25. The method of any one of claims 1 to 24, wherein the L-glufosinate ammonium monohydrate form B is characterized by a differential scanning calorimetry (DSC) curve exhibiting an endotherm with an onset at 123°C.

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