Process for the preparation of alpha-hydroxy esters by grignard coupling and thiolation reactions

Abstract

To provide a method for producing an α - hydroxyester by using an inexpensive and nontoxic reactant under a mild reaction condition.SOLUTION: A process for the preparation of α - hydroxy esters by addition of vinyl Grignard reagents to oxalate esters and thiolation of the resulting double bonds, or a process for the preparation of α - hydroxy esters wherein a compound of formula (II) is reduced with a reducing agent selected from NaBH4, LiBH4 and Al (O-iPr) 3 / iPrOH. Further provided are alpha-hydroxy esters and synthetic intermediates produced according to the disclosed methods, as well as compositions comprising the alpha-hydroxy esters.SELECTED DRAWING: Figure 3B

Description

[Technical Field]

[0001] Related Applications This application claims priority to International Application No. PCT / CN2019 / 120393, filed November 22, 2019, which is incorporated herein by reference in its entirety for all purposes.

[0002] The present disclosure provides methods for producing α-hydroxy esters by adding a vinyl Grignard reagent to an oxalate ester and thiolating the resulting double bond. Also provided are α-hydroxy esters and synthetic intermediates produced according to the methods disclosed herein, compositions containing the α-hydroxy esters, and methods of using the compositions. [Background technology]

[0003] Alpha-hydroxyester analogs of natural amino acids are useful as dietary supplements and in the study of enzymatic processes and protein function. The synthesis of such esters typically involves acid-catalyzed Fischer esterification of the corresponding acid with an alcohol in the presence of a strong acid, such as H2SO4 or Amberlyst® cation exchange resin, acid-mediated hydrolysis of the corresponding nitrile in the presence of a strong acid, or enzyme-mediated methods. However, acid-catalyzed procedures result in decomposition of the starting materials and products, as well as contamination of the products with dimeric and oligomeric components. Such methods generally result in low yields, and complex purification techniques are required to isolate the target compound from polymeric by-products. Enzymatic methods require expensive and unstable reactants and special reaction conditions.

[0004] A particularly important α-hydroxy ester is isopropyl 2-hydroxy-4-(methylthio)butanoate (HMBi). HMBi is the isopropyl ester of 2-hydroxy-4-(methylthio)butanoic acid (HMBA), a hydroxy analog of methionine. HMBi is used to aid in methionine supplementation in ruminants, including cows. Ensuring sufficient levels of methionine in dairy cows helps maintain desirable levels of milk protein synthesis and, therefore, milk production. However, the methionine content in animal feeds is largely inadequate, making it a major limiting factor in dairy cow diets. HMBi is a chemical derivative of methionine that readily and rapidly diffuses through the rumen wall, avoiding degradation by ruminal microorganisms. Once HMBi penetrates the rumen wall, it is metabolized by the liver and becomes available for milk protein synthesis in dairy cows.

[0005] There is a need for additional methods for synthesizing α-hydroxy esters, such as HMBi, that use inexpensive, non-toxic reactants and mild reaction conditions, and that provide product esters in high yield and purity. Summary of the Invention

[0006] In one aspect, the present disclosure provides: Formula (I): [ka] (In the formula, R 1 is C 1~4 is alkyl, R 2 is C 1~8 Alkyl or C 4~7 is cycloalkyl, R 3 and R 4 are each independently selected from H, methyl, and ethyl. A method for producing a compound of the formula Formula (IV): [ka] with a compound of formula (A): [ka] (wherein X is Br or Cl) by coupling with a vinyl Grignard reagent of formula (III): [ka] and forming a compound of converting the compound of formula (III) to the compound of formula (I); The present invention relates to the above method, which includes:

[0007] In one aspect, the present disclosure provides a method for preparing a compound of formula (I), comprising: Formula (II): [ka] with a reducing agent to form a compound of formula (I) above.

[0008] In some embodiments, the compound of formula (I) above has the formula (IA): [ka] is a compound of

[0009] In another aspect, the present disclosure provides a compound of formula (IA): [ka] A method for producing a compound of the formula esterifying oxalic acid with isopropanol to form diisopropyl oxalate; Diisopropyl oxalate is coupled with vinylmagnesium bromide to give formula (III-A): [ka] and forming a compound of The compound of formula (III-A) above is thiolated with CH3SH to obtain the compound of formula (II-A): [ka] and forming a compound of reducing the compound of formula (II-A) to form a compound of formula (IA) above; The present invention relates to the above method, which includes:

[0010] In another aspect, the disclosure is directed to a compound of Formula (I) or Formula (IA) prepared according to any of the methods described herein.

[0011] In another aspect, the present disclosure is directed to isopropyl 2-oxobut-3-enoate.

[0012] In another aspect, the present disclosure is directed to an animal feed composition comprising a compound of Formula (I) or Formula (IA) described herein. In some embodiments, the animal feed is a cattle feed, such as a dairy cattle feed.

[0013] In another aspect, the disclosure is directed to a method of providing bioavailable methionine to a dairy cow, the method comprising administering to the cow a compound of Formula (I) or Formula (IA) or an animal feed composition described herein. In another aspect, the disclosure is directed to a method of providing at least about 50% bioavailable methionine to a dairy cow, the method comprising administering to the cow a compound of Formula (I) or Formula (IA) or an animal feed composition described herein. In another aspect, the disclosure is directed to a method of improving milk obtained from a dairy cow, the method comprising administering to the cow a compound of Formula (I) or Formula (IA) or an animal feed composition described herein.

[0014] In another aspect, the present disclosure is directed to a method of improving the condition of a cow, comprising feeding said cow a compound of Formula (I) or Formula (IA) or an animal feed composition described herein. [Brief explanation of the drawings]

[0015] [Figure 1A] FIG. 1A is the 13C NMR spectrum of diisopropyl oxalate described in Example 1. [Figure 1B] FIG. 1B is a 1H NMR spectrum of diisopropyl oxalate described in Example 1. [Figure 2A] FIG. 2A is a 13C NMR spectrum of 2-oxo-4-methylthiobutanoic acid isopropyl ester described in Example 3. [Figure 2B] FIG. 2B is a 1H NMR spectrum of 2-oxo-4-methylthiobutanoic acid isopropyl ester described in Example 3. [Figure 3A] FIG. 3A is a 13C NMR spectrum of 2-hydroxy-4-methylthiobutanoic acid isopropyl ester (HMBi) described in Example 5. [Figure 3B] FIG. 3B is a 1H NMR spectrum of 2-hydroxy-4-methylthiobutanoic acid isopropyl ester (HMBi) described in Example 5. DETAILED DESCRIPTION OF THE INVENTION

[0016] Unless otherwise specified, terms in this disclosure are used in accordance with their meanings as understood by those of ordinary skill in the art. Terms have their plain and ordinary meaning. The following terms used in the specification and claims are defined for purposes of this disclosure and have the following meanings:

[0017] As used herein, the terms "isopropyl 2-hydroxy-4-(methylthio)butanoate," "HMBi," and "isopropyl ester of 2-hydroxy-4-(methylthio)butanoic acid" refer to the isopropyl ester of 2-hydroxy-4-(methylthio)butanoic acid having the following structure (shown below as formula (IA), R 1 is methyl and R 2 is isopropyl. [ka]

[0018] As used herein, the terms "2-hydroxy-4-(methylthio)butanoate," "2-hydroxy-4-(methylthio)butanoic acid," and "HMBA" refer to a compound of the following structure: [ka]

[0019] The compounds described herein may exist in racemic form, as a single enantiomer, or as a mixture of enantiomers. Thus, for example, HMBi refers to racemic HMBi (i.e., "DL-HMBi"), or D-HMBi or L-HMBi, or mixtures thereof.

[0020] The compounds described herein may also exist in the form of salt.It should be understood that the chemical formulas shown herein include the structures shown as well as their salt forms.For example, if a compound contains carboxylic acid, the formula also includes the salt form (carboxylate) of its conjugate base, such as sodium salt, potassium salt, magnesium salt or calcium salt.If a compound contains indole group or imidazole group, the formula also includes the salt of its conjugate acid, for example, HCl salt.

[0021] "Alkyl" means a linear, saturated, monovalent hydrocarbon radical of 1 to 8 carbon atoms (e.g., 1 to 6 carbon atoms, 1 to 4 carbon atoms, or 1 to 3 carbon atoms) or a branched, saturated, monovalent hydrocarbon radical of 3 to 8 carbon atoms (e.g., 3 to 6 carbon atoms, 3 to 4 carbon atoms, or 3 carbon atoms), such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl (including all isomeric forms), and the like.

[0022] "Cycloalkyl" means a cyclic, saturated, monovalent hydrocarbon radical of three to ten carbon atoms, e.g., cyclopropyl, cyclobutyl, cyclopentyl, or cyclohexyl.

[0023] "Optional" or "optionally" means that the subsequently described event or circumstance may occur, but need not necessarily occur, and the statement encompasses both cases where the event or circumstance occurs and cases where it does not occur. For example, an alkyl group "optionally substituted with -OH" means that -OH may be present, but need not necessarily be present, and the statement encompasses both cases where the alkyl group is substituted with an -OH group and cases where the alkyl group is not substituted with an -OH group.

[0024] The term "reaction solvent" refers to an organic liquid used to carry dissolved reactants. In some embodiments, one of the reactants in the reaction functions as both a reactant and a reaction solvent. In other embodiments, the reactants are diluted with a different reaction solvent.

[0025] The term "acid catalyst" refers to an acid that is added to a reaction in a substoichiometric amount and functions to catalyze the reaction. The acid catalyst may be a Bronsted acid (such as an acid with a pKa less than 7, e.g., HCl, H2SO4, KHSO4, acetic acid, etc.) or a Lewis acid (such as a boronic acid). In some embodiments, the acid is generated in situ, for example, by reaction of acetyl chloride or TMSCl with water or an alcohol.

[0026] The term "concentration" refers to the amount of solute in a solvent. As used herein, concentration may be expressed in terms of weight percent or in terms of molarity (M) or normality (N).

[0027] The terms "heptane" or "n-heptane" refer to pure n-heptane or n-heptane in a mixture with other C7 isomers (e.g., at least 90% n-heptane and at least 95% total C7 isomers).

[0028] The term "reflux temperature" or "reflux" refers to the temperature at which the reaction solvent boils; a condenser is usually used to cool and condense the solvent vapors back into the reactor. The exact temperature at which a given solvent reaches reflux can vary depending on environmental factors.

[0029] The term "about" refers to numerical values, including, for example, integers, fractions, and percentages, whether or not explicitly indicated. The term "about" generally refers to a range of numerical values ​​(e.g., ±5-10% of the recited numerical value) that one of ordinary skill in the art would consider equivalent to the recited value (e.g., having a similar function or result). When terms such as "at least" and "about" precede a recitation of numerical values ​​or ranges, the term modifies all values ​​or ranges set forth in the recitation. In some cases, the term "about" may encompass rounded numerical values.

[0030] The terms "extract," "extraction," or "extracting" refer to the process of partitioning a substance between an organic phase and an aqueous phase. In some embodiments, the extracting is performed on the reaction mixture or a concentrated residue of the reaction mixture. An "extract" is the organic phase once separated from the aqueous phase. As used herein, extracting does not include purification methods performed on the crude reaction product, such as simple distillation, vacuum distillation, azeotropic distillation, fractional distillation, sequential distillation, flash chromatography, HPLC, or recrystallization.

[0031] As used herein, "purification" or "purifying" refers to a method of isolating the product of a reaction after the reaction is complete. Purification methods include simple distillation, vacuum distillation, azeotropic distillation, fractional distillation, continuous distillation, flash chromatography, HPLC, or recrystallization.

[0032] The term "substantially", eg, "substantially in monomeric form", refers to the purity of the compound of formula (I) with respect to dimeric and / or oligomeric analogs.

[0033] As used herein, the term "dimer" or "dimeric compound" refers to a compound in which two molecules of a given monomer structure, or one molecule each of two different monomer structures, are condensed into a single molecule. As used herein, the term "oligomer" or "oligomeric compound" refers to a compound in which three or more molecules of a given monomer structure, or three or more molecules of at least two different monomer structures, are condensed into a single polymeric structure. HMBi may form homo- or hetero-HMBi oligomers (containing at least one HMBi monomer unit).

[0034] The term "purity" or a percentage of a compound (e.g., x% HMBi) refers to the purity of a compound in a sample as measured by weight, by GC analysis, and / or by HPLC analysis. In some embodiments, the purity by weight is measured by GC or HPLC analysis with UV detection.

[0035] The term "purity by weight" refers to the purity of a compound in a sample with respect to other components in the sample, expressed as a ratio of the mass of the compound to the mass of the sample, expressed as a percentage.

[0036] The term "purity," with respect to gas chromatography (GC) purity or HPLC purity, refers to the calculated purity (expressed as a percentage) of the peak area of ​​the compound of interest relative to the sum of all peak areas in a chromatogram. In some embodiments, purity is measured by HPLC with UV detection.

[0037] In some embodiments, the purity is that required to comply with regulations for the sale of regulated products. For example, in the case of HMBi, the compound contains 0.5% or less water (e.g., as measured by Karl Fischer analysis). (See Commission Implementing Regulation (EU) No. 469 / 2013 of May 22, 2013.)

[0038] The terms "crude," "crude product," and "crude compound" refer to a sample of compound obtained from a reaction mixture after concentration of the reaction mixture and / or after extraction of the reaction mixture into an organic solvent and concentration of the organic extract.

[0039] The term "animal feed composition" refers to a product suitable for use in animal nutrition. In some embodiments, the animal feed composition is an animal feed (e.g., food or drinking water containing a nutritional supplement), and in some embodiments, the animal feed composition is a feed additive. The feed additive is suitable for mixing with animal feed or drinking water.

[0040] The term "carrier" refers to a carrier suitable for animal feed additives. Suitable carriers include water (for liquid or solid feed additives) or silica (for solid feed additives). In some embodiments, the carrier is silica (silicon dioxide). In some embodiments, the feed additive comprises the compound and silica in a 3:2 ratio.

[0041] In some embodiments, the animal feed comprises a granulated, protein-rich feed (e.g., peanut-based, rapeseed meal-based, and / or soybean meal-based) supplemented with 2.5% or 1% by weight of HMBi. In some embodiments, the animal feed comprises about 45% and about 50% grain (corn, barley, wheat, and / or wheat by-products) supplemented with 0.5% or 3.0% by weight of HMBi. In some embodiments, the animal feed comprises a meal or granulated feed containing molasses, supplemented with 2.5% or 1% by weight of HMBi, respectively.

[0042] The term "administering" refers to providing a nutritional supplement to a subject animal. Administering may be performed orally, for example, through ingestion of food or drinking water containing the compound, or by injection or other modes of administration.

[0043] As used herein, "improving milk" refers to improving the quality and / or quantity of milk produced by a treated cow or group of treated cows compared to milk produced by untreated control animals. Milk improvements include, for example, increasing the protein content of the milk (e.g., increasing alpha, beta, and / or kappa protein), increasing the fat content of the milk, and / or increasing the volume of milk produced.

[0044] As used herein, "improving cattle condition" refers to an improvement in the health index of a treated cattle or a group of treated cattle compared to the health index of untreated control animals. Improvement in cattle condition may refer, for example, to an increase in some characteristic, such as weight, compared to untreated animals.

[0045] As used herein, "improving fertility" includes, for example, shortening the interval between birth and reproduction and / or increasing fertility during insemination.

[0046] As used herein, "improving liver function" includes, for example, reducing metabolic problems, improving very low density lipoprotein levels, reducing hyperketonemia, and / or reducing the incidence of fatty liver.

[0047] As used herein, "increased energy" refers to, for example, stimulation of fermentation processes in the rumen, leading to an increase in digestible organic matter and thus more energy for the animal.

[0048] Synthesis Process The present disclosure provides a method for preparing compounds of formula (I) or formula (IA) and / or intermediates, comprising the steps of: a) R of oxalyl chloride or oxalic acid 2 Esterification with -OH to form oxalic acid diesters, b) Coupling of the above oxalic acid diester with an alkenyl Grignard reagent to form an alkenyl-substituted α-ketoester (2-oxobut-3-enoate ester); c) thiolation of the alkenyl-substituted α-ketoester to form a 4-alkylthio-2-oxo-butanoic acid ester, and d) Reduction of the 4-alkylthio-2-oxo-butanoic acid ester to form a compound of formula (I) or formula (IA) The oxalic acid can be used, for example, as oxalic acid or oxalic acid dihydrate.

[0049] In some embodiments, the present disclosure provides: Formula (I): [ka] (In the formula, R 1 is C 1~4 is alkyl, R 2 is C 1~8 Alkyl or C 4~7 is cycloalkyl, R 3 and R 4 are each independently selected from H, methyl, and ethyl. A method for producing a compound of the formula Formula (IV): [ka] with a compound of formula (A): [ka] (wherein X is Br or Cl) by coupling with a vinyl Grignard reagent of formula (III): [ka] and forming a compound of converting the compound of formula (III) to the compound of formula (I); The present invention relates to the above method, which comprises:

[0050] In some embodiments, the present disclosure relates to a method for preparing a compound of formula (III), comprising coupling a compound of formula (IV) with a vinyl Grignard reagent of formula (A).

[0051] In some embodiments, R 1 is methyl.

[0052] In some embodiments, each R 2 is selected from methyl, ethyl, and isopropyl. In some embodiments, each R 2 is isopropyl.

[0053] In some embodiments, R 3 and R 4 are H respectively.

[0054] In some embodiments, the compound of formula (I) above has the formula (IA): [ka] is a compound of

[0055] In some embodiments, the compound of formula (III) above has the formula (III-A): [ka] is a compound of

[0056] In some embodiments, the vinyl Grignard reagent of formula (A) above is vinyl-MgCl. In some embodiments, X is Cl. In some embodiments, the Grignard coupling is carried out in the presence of a salt additive such as LiCl or ZnCl. In some embodiments, the salt additive is LiCl.

[0057] In some embodiments, the coupling comprises combining the compound of Formula (IV) with about 0.8 to about 2.0 molar equivalents, or about 1.0 to about 1.75 molar equivalents, or about 1.0 to about 1.5 molar equivalents, or about 1.2 to about 1.75 molar equivalents, or about 1.4 to about 1.6 molar equivalents, or about 1.5 molar equivalents of the vinyl Grignard reagent of Formula (A).

[0058] In some embodiments, the coupling is carried out at a temperature ranging from about −80° C. to about 10° C., or from about −80° C. to about −70° C., or from about −50° C. to about 10° C., or from about −40° C. to about 5° C., or from about −50° C. to about −20° C., or from about −30° C. to about −20° C., or at a temperature of about −78° C., or about −20° C., or about 0° C. In some embodiments, the coupling comprises mixing a solution of the compound of Formula (IV) in MTBE with about 1.5 molar equivalents of the vinyl Grignard reagent of Formula (A) at a temperature of about −50° C. to about −20° C., or from about −30° C. to about −20° C. In some embodiments, the vinyl Grignard reagent is added slowly and / or in portions to the compound of Formula (IV).

[0059] In some embodiments, the coupling is carried out in an aprotic solvent. In some embodiments, the aprotic solvent is an ether such as MTBE, THF, or EtO, optionally mixed with a nonpolar solvent such as heptane or hexane. In some embodiments, the aprotic solvent is MTBE or THF, optionally mixed with heptane. In some embodiments, the concentration of the coupling reaction is about 0.25 M to about 1.3 M (moles of the compound of Formula (IV) per liter of reaction solvent), or about 0.4 M to about 1.1 M, or about 0.4 M to about 0.5 M, or about 0.9 M to about 1.0 M, or about 0.5 M, or about 1 M. .

[0060] In some embodiments, the coupling step converts the compound of formula (III) to a compound of formula (III-Z): [ka] wherein the mixture has a ratio of (III):(III-Z) of at least 5:1, or at least 6:1, or at least 7:1, or at least 8:1, or at least 9:1, or at least 10:1, or at least 15:1, or at least 20:1.

[0061] In some embodiments, converting the compound of formula (III) to the compound of formula (I) comprises reacting a compound of formula (B) or formula (C): R 1 -SH (B) R 1 -S - M + (C) (In the formula, M + is a metal cation) The compound of formula (III) is thiolated with a thiolating agent to obtain a compound of formula (II): [ka] and forming a compound of reducing the compound of formula (II) to form the compound of formula (I); Includes:

[0062] In some embodiments, the present disclosure relates to a method for preparing a compound of Formula (II), comprising thiolating a compound of Formula (III) with a thiolating agent of Formula (B) or Formula (C).

[0063] In some embodiments, the thiolation is carried out with a thiolation agent of formula (B) in the presence of an additive. In some embodiments, the additive is an amine base such as triethylamine, diethylamine, pentylamine, or hexylamine, a phosphine such as dimethylphenylphosphine (DMPP) or tris(2-carboxyethyl)phosphine (TCEP), a basic salt such as NaHCO or NaCO, a Lewis acid such as scandium(III) triflate or anhydrous cerium(III) chloride, or an N-heterocyclic carbene (NHC) complex (e.g., Au-NHC complex). In some embodiments, the additive is triethylamine.

[0064] In some embodiments, the method further comprises generating a thiolation agent of formula (B) from the thiolation agent of formula (C). In some embodiments, the generating is performed in the presence of an acid catalyst. In some embodiments, the acid catalyst is acetic acid, p-toluenesulfonic acid, or H2SO4. In some embodiments, the thiolation is carried out at a temperature ranging from about -40°C to about 10°C, or from about -35°C to about 5°C, or from about -30°C to about -20°C, or at about 0°C.

[0065] In some embodiments, the thiolation agent is of Formula (C), and the thiolation is carried out at a temperature ranging from about -80°C to about 35°C, or from about 15°C to about 35°C.

[0066] In some embodiments, M + Na + or K + is.

[0067] In some embodiments, the coupling step comprises extracting the compound of formula (III) into an organic solvent to form an extract of formula (III), and the thiolation step comprises adding the thiolation agent to the extract of formula (III). Thus, the thiolation reaction is carried out without purifying the intermediate of formula (III) derived from the coupling reaction prior to the thiolation reaction. In some embodiments, the procedure is as follows: [ka]

[0068] In some embodiments, reducing the compound of Formula (II) is carried out in the presence of a reducing agent selected from NaBH4, LiBH4, and Al(O-iPr)3 / iPrOH. In some embodiments, the reducing agent is NaBH4. In some embodiments, the thiolation comprises extracting the compound of Formula (II) into an organic solvent to form an extract of Formula (II), and the reduction comprises adding the reducing agent to the extract of Formula (II). Thus, the reduction is carried out without purifying the compound of Formula (II) prior to the reduction. In some embodiments, the coupling comprises extracting the compound of Formula (III) into an organic solvent to form an extract of Formula (III), the thiolation comprises adding the thiolation agent to the extract of Formula (III) and extracting the compound of Formula (II) into an organic solvent to form an extract of Formula (II), and the reduction comprises adding the reducing agent to the extract of Formula (II). Thus, as shown in the following scheme, the coupling, thiolation, and reduction are carried out without purifying the intermediates of formula (II) and formula (III). [ka]

[0069] In some embodiments, the reducing step comprises: (a) In an alcoholic solvent such as methanol, ethanol, or isopropanol and / or (b) using about 0.25 to about 1.0 molar equivalents of a reducing agent, and / or (c) at a temperature in the range of about -10°C to about 30°C, or at about 0°C; This is done using NaBH4 or LiBH4.

[0070] In some embodiments, the reducing is carried out at a temperature ranging from about 50°C to about 90°C, or at about 80°C, using Al(O-iPr)3 / iPrOH.

[0071] In some embodiments, the method further comprises reacting oxalyl chloride with R 2 -OH to form a compound of formula (IV). In some embodiments, the esterifying is carried out in the presence of at least one amine base, such as N,N-dimethylpyridine, pyridine, or triethylamine. In some embodiments, the esterifying is carried out at a temperature ranging from about -5°C to about 30°C.

[0072] In some embodiments, the process comprises the step of reacting R 2 with 2-methyl-2-propanol in the presence of an acid catalyst and an optional dehydrating agent such as azeotropic water removal, molecular sieves, or a combination thereof. 2The method further comprises esterifying oxalic acid with —OH to form a compound of formula (IV). In some embodiments, the acid catalyst is selected from p-TsOH; H2SO4; macroporous sulfonic acid resin catalysts such as Amberlyst®-15, Dowex®, or M32; silicoaluminates; phosphoric acid; boronic acid; acetyl chloride; and acids with a pKa of less than 3. In some embodiments, the acid catalyst is p-TsOH or H2SO4. In some embodiments, the acid catalyst is about 0.01 to about 0.1 molar equivalents, or about 0.025 to about 0.05 molar equivalents of p-TsOH, or about 1 to about 3 molar equivalents, or about 2 molar equivalents of H2SO4. In some embodiments, the esterifying is performed at the reflux temperature of the reaction solvent. In some embodiments, the esterifying is performed in a reaction solvent selected from toluene, CHCl3, and isopropanol.

[0073] In some embodiments, the present disclosure provides a compound of formula (I): [ka] (In the formula, R 1 is C 1~4 is alkyl, R 2 is C 1~8 Alkyl or C 4~7 is cycloalkyl, R 3 and R 4 are each independently selected from H, methyl, and ethyl. A method for producing a compound of the formula Formula (II): [ka] In some embodiments, the compound of formula (I) is a compound of formula (IA). In some embodiments, the compound of formula (II) is a compound of formula (II-A): [ka] is a compound of

[0074] In some embodiments, reducing the compound of Formula (II) is carried out in the presence of a reducing agent selected from NaBH, LiBH, and Al(O-iPr) / iPrOH, and in some embodiments, the reducing agent is NaBH.

[0075] In some embodiments, the reducing step comprises: (a) in an alcoholic solvent such as methanol, ethanol, or isopropanol, and / or (b) using about 0.25 to about 1.0 molar equivalents of a reducing agent, and / or (c) at a temperature in the range of about -10°C to about 30°C, or at about 0°C; This is done using NaBH4 or LiBH4.

[0076] In some embodiments, the reducing is carried out at a temperature ranging from about 50°C to about 90°C, or at about 80°C, using Al(O-iPr)3 / iPrOH.

[0077] In some embodiments, the method comprises reacting a compound of formula (III): [ka] (In the formula, R 3 and R 4 are each independently selected from H, methyl, and ethyl. of formula (B) or formula (C): R 1 -SH (B) R 1 -S - M + (C) (In the formula, M + is a metal cation) to form a compound of formula (II). In some embodiments, the compound of formula (II) is a compound of formula (II-A), and the compound of formula (III) is a compound of formula (III-A): [ka] is a compound of

[0078] In some embodiments, the present disclosure provides a compound of formula (IA): [ka] A method for producing a compound of the formula esterifying oxalic acid with isopropanol to form diisopropyl oxalate; Diisopropyl oxalate is coupled with vinylmagnesium bromide to give formula (III-A): [ka] and forming a compound of The compound of formula (III-A) above is thiolated with CH3SH to obtain the compound of formula (II-A): [ka] and forming a compound of reducing the compound of formula (II-A) to form a compound of formula (IA) above; The present invention relates to the above method, which comprises:

[0079] In some embodiments, the methods described herein provide compounds of Formula (I) or Formula (IA) with a purity of at least about 95% by GC, HPLC, and / or weight. In some embodiments, the methods provide crude compounds of Formula (I) or Formula (IA) that are at least about 95%, or at least about 96%, or at least about 97%, or at least about 98% pure by weight, GC, and / or HPLC, where the crude compounds are unpurified or purified only by fractional distillation. In some embodiments, the methods provide crude compounds of Formula (I) or Formula (IA) that are substantially in monomeric form or contain less than about 5% by weight, or less than about 3% by weight, of dimeric and / or oligomeric compounds. % by weight of a crude compound of formula (I) or formula (IA), said crude compound being unpurified or purified only by fractional distillation.

[0080] compound products In some embodiments, the reacting provides a crude compound of Formula (I), unpurified or purified only by fractional distillation, that is at least about 80% pure by weight (and / or by GC or HPLC), or at least about 90% pure by weight, or at least about 95% pure by weight, or at least about 96% pure by weight, or at least about 97% pure by weight, or at least about 98% pure by weight. In some embodiments, the reacting provides a crude compound of Formula (I) or Formula (IA), unpurified or purified only by fractional distillation, that is substantially in monomeric form or contains less than about 5% by weight or less than about 3% by weight of dimeric and / or oligomeric compounds.

[0081] In some embodiments, the disclosure relates to compounds of Formula (I) or Formula (IA) prepared as described herein. In some embodiments, the disclosure relates to compounds of Formula (I) or Formula (IA) that are at least about 80%, or at least about 90%, or at least about 95%, or at least about 96%, or at least about 97%, or at least about 98% pure by weight (and / or by GC or HPLC), and that are unpurified or purified only by fractional distillation. In some embodiments, the compounds are substantially in monomeric form or contain less than about 5% by weight, or less than about 3% by weight, of dimeric and / or oligomeric compounds.

[0082] In some embodiments, the HMBi (Formula (IA)) product has one or more of the following specifications: (a) an HMBi monomer content and chemical purity of at least about 95%, by weight or HPLC analysis; (b) a water content of less than about 0.5%, by Karl Fischer analysis; and (c) a pH of less than about 6.0 (measured at a 1% concentration in water).

[0083] Also disclosed herein are compounds of Formula (I) or Formula (IA) prepared by any of the methods described herein. In some embodiments, compounds of Formula (I) or Formula (IA) are present that are at least about 95% pure by weight (and / or by GC or HPLC), or at least about 96%, or at least about 97%, or at least about 98% pure, crude, unpurified, and / or purified only by fractional distillation. In some embodiments, the compounds are present in a form comprising R 1 is -CH2CH2-S-CH3, and R 2 is isopropyl, or the compound is a compound of formula (IA). In some embodiments, the compound is substantially in monomeric form or contains less than about 5% by weight, or less than about 3% by weight, of dimeric and / or oligomeric compounds.

[0084] Animal feed compositions and uses In some aspects, the present disclosure relates to an animal feed composition comprising a compound of Formula (I) or Formula (IA) described herein. In some embodiments, the animal feed composition is suitable for administration to ruminants such as cattle, cows, sheep, antelope, deer, giraffe, bovine animals (e.g., bison, buffalo, or yak), goats, and / or gazelles. In some embodiments, the animal feed composition is a cattle feed composition, such as a dairy cattle feed composition, or an additive for cattle feed, such as dairy cattle feed. In some embodiments, the animal feed composition is a dairy cattle feed composition.

[0085] In some embodiments, the animal feed composition is an animal feed or an animal feed additive. In some embodiments, the animal feed additive is in liquid or solid form, the liquid form comprising the compound and optionally a liquid carrier, and the solid form comprising the compound mixed with a solid carrier, optionally the solid carrier being silica (silicon dioxide), and optionally the ratio of the compound to the solid carrier is about 5:1 to about 1:5, or about 3:2. In some embodiments, the feed composition is a liquid feed additive or a solid feed additive. In some embodiments, the animal feed composition is a drinking water additive. In some embodiments, the pH of the liquid feed additive or drinking water additive is in the range of about 4.0 to about 7.5.

[0086] In some embodiments of the animal feed composition, R 1 is -CH2CH2-S-CH3, and R 2 is isopropyl. In some embodiments, the compound is of formula (IA).

[0087] In some embodiments, the disclosure relates to a method for providing bioavailable methionine to a dairy cow, the method comprising administering to the cow a compound or animal feed composition described herein. In some embodiments, administering comprises feeding the cow a feed composition comprising the compound. In some embodiments, the disclosure relates to a method for providing at least about 50% bioavailable methionine to a dairy cow, the method comprising administering to the cow a compound or animal feed composition described herein. In some embodiments, the disclosure relates to a method for improving milk obtained from a dairy cow, the method comprising feeding the cow a compound or animal feed composition described herein. In some embodiments, the improvement in the milk comprises increasing the protein content in the milk. In some embodiments, the improvement in the milk comprises increasing the fat content in the milk. In some embodiments, the disclosure relates to a method for improving the condition of a cow, the method comprising feeding the cow a compound or animal feed composition described herein. In some embodiments, the improvement in the condition of the cow comprises improving fertility. In some embodiments, the improvement in the condition of the cow comprises improving liver function. In some embodiments, the improvement in the condition of the cow comprises increasing energy.

[0088] In some embodiments, any of the reactions described herein may be carried out using a continuous flow apparatus. [Example]

[0089] Apparatus: All millimole-scale experiments were carried out using a 100 mL or 250 mL three-neck round-bottom flask equipped with a magnetic stirrer, dropping funnel, and thermometer. The reaction flask was equipped with a condenser and a thermometer to monitor the reaction temperature. When reactions were carried out at reflux, a silicone oil bath was used to heat the reaction mixture. For experiments at temperatures below room temperature, a liquid nitrogen bath or a salt / ice mixture bath was used. All kg-scale experiments were carried out using a 5 L jacketed reactor. Concentration and / or purification of intermediates and crude products was carried out using a laboratory-scale vacuum distillation apparatus, rotary evaporator, or column chromatography, or as otherwise specified in the examples below.

[0090] Example 1: Synthesis of diisopropyl oxalate from oxalic acid [ka]

[0091] In a 5 L laboratory reactor, oxalic acid (1 kg, 11.1 mol) was added to isopropyl alcohol (1700 mL) under stirring. A clear solution formed. A solution of p-toluenesulfonic acid monohydrate (47.67 g, 2.5 mol%) in toluene (200 mL) was then slowly added. The reaction mixture was heated and stirred under reflux for 24 h. The water formed was continuously removed azeotropically using a Dean-Stark trap to drive the reaction to completion. The reaction mixture was cooled, neutralized with 500 mL of saturated aqueous NaHCO3, and partitioned between 400 mL of toluene and 1 L of water (twice). The combined organic phase was dried with 1 L of saturated aqueous NaCl. The organic phase was separated, and the solvent was removed under reduced pressure. The crude material was purified by distillation under high vacuum with heat to give 1740 g (90%) of diisopropyl oxalate as a colorless oil. 13 C NMR (100 MHz, CDCl3) δ (ppm) 157.96, 71.44, 21.63 (Fig. 1A); 1 H NMR (400 MHz, CDCl3)δ 5.13 (hept, J = 6.3 Hz , 2 H), 1.33 (d, J = 6.2 Hz, 12 H) (Figure 1B).

[0092] Various other suitable reaction conditions were investigated using oxalic acid dihydrate (sequential numbers 1–5) or oxalic acid (sequential numbers 6–7) as starting materials, as shown in Table 1. 4 Å molecular sieves (1–2 g per 5 g of starting material) were added to the reaction mixture to further remove water during the reaction. Workup included diluting the reaction mixture with ethyl acetate, neutralizing to pH 7 with saturated aqueous NaHCO3, separating the layers, washing the organic extract with saturated aqueous NaHCO3 and saturated aqueous NaCl, and concentrating to obtain a crude residue. [Table 1]

[0093] Example 2: Synthesis of diisopropyl oxalate from oxalyl chloride [ka]

[0094] To a 3 L sample of isopropyl alcohol at 0°C in a 5 L glass-lined laboratory reactor, oxalyl chloride (1019 g) was added slowly in portions under stirring, while maintaining the temperature between 0 and 5°C. After the addition was complete, the reaction mixture was allowed to warm to room temperature and stirred for 12 h. The mixture was concentrated by rotary evaporation and high vacuum to give a crude product. The crude product was diluted with dichloromethane (1000 mL) and washed with saturated aqueous NaHCO3 (3 × 500 mL) to give an organic extract. The first two aqueous washes were back-extracted with dichloromethane (1 L each) to give two additional organic extracts. These three organic extracts were dried with saturated aqueous NaCl (3 × 500 mL), combined, concentrated, and purified by distillation to give diisopropyl oxalate in 86% yield. 1H NMR (400 MHz, CDCl3) δ 5.13 (hept, J = 6.3 Hz, 2 H), 1.33 (d, J = 6.2 Hz, 12 H).

[0095] As shown in Table 2, various other suitable reaction conditions were investigated. [Table 2]

[0096] Example 3: Synthesis of 2-oxo-4-methylthiobutanoic acid isopropyl ester (small scale experiment) [ka]

[0097] Step 1, Grignard Reaction: A mixture of diisopropyl oxalate (1.4 g, 8 mmol, 1.0 equiv.), 16 mL of solvent (MTBE, MTBE / heptane mixture, or THF), and 2 equiv. of LiCl (0.68 g, 16 mmol, if used) was cooled to the test temperature (shown in Table 3) either under a liquid nitrogen bath or a salt bath. A solution of vinylmagnesium chloride (1.6 M in THF) was slowly added, and the resulting mixture was stirred until the starting material was consumed (see Table 3). The reaction mixture was quenched by washing with saturated aqueous NH4Cl (2 × 100 mL). The product was extracted with EtOAc (2 × 100 mL), dried over Na2SO4, and filtered. The yield of 2-oxo-3-butenoic acid isopropyl ester was determined by GC / MS. This extract was used directly in the next step without further purification. [Table 3]

[0098] Step 2, thiolation reaction

[0099] Procedure 1: As shown in Table 4, CH3SH gas was generated by treating a 20% w / v aqueous solution of CH3SNa with an acid catalyst (AcOH (12 mmol) or TsOH (12 mmol)) at -30 to -20 °C or with H2SO4 (2 equivalents relative to CH3SNa) at 50 °C for 15 to 30 min. The generated CH3SH was bubbled into a stirred solution of MTBE (20 mL) containing triethylamine (0.1 mL) at 0 °C. The resulting MTBE solution of CH3SH was added to a MTBE solution of the crude product from Step 1, Table 3, serial no. 14, at 0 °C or -30 to -20 °C, as shown in Table 4, and the reaction mixture was stirred for 15 to 30 min. The reaction mixture was quenched with 2 M HCl, extracted with ethyl acetate, dried (Na2SO4), filtered, and concentrated. The crude material was then used in the next reaction step.

[0100] In Table 4, serial numbers 1-5, CH3SH gas was generated using acetic acid or p-toluenesulfonic acid. In serial numbers 1-3, the yield is the isolated yield after column chromatography. In serial numbers 4-5, the yield is the isolated yield after distillation of the product. In serial numbers 6-9, CH3SH gas was generated by heating a 20% aqueous solution of CH3SNa and H2SO4 at 50°C. [Table 4]

[0101] Procedure 2: To a solution of the crude product from Step 1, Table 3, Serial No. 11 in THF at -78 °C, 20% w / v aqueous CHSNa (1 equivalent) and HSO (2 equivalents) were added. The reaction mixture was allowed to warm to room temperature and stirred for 16 h. The reaction mixture was quenched with 2 M HCl, extracted with ethyl acetate (2 × 50 mL), dried (NaSO), filtered, and concentrated. The crude product was then used in the next reaction step. The product was isolated to give a 33% yield. 1 H NMR (400 MHz, CDCl3) δ 5.12 (hept, J = 6.2 Hz, 1 H), 3.13 (t, J = 7.2 H z, 2 H), 2.76 (t, J = 7.2 Hz, 2 H), 2.11 (s, 3 H), 1.33 (d, J = 6.3 Hz, 6 H).

[0102] Step 3, continuous flow reactor: Alternatively, a mixture of 2-oxo-3-butenoic acid isopropyl ester and 10 mL of triethylamine is pumped into the reactor at a controlled flow rate. The outlet is further connected to the inlet of a Y-shaped mixer, into which another inlet is fed with MeSH gas (at a controlled flow rate). The two components are then mixed and further stirred in the batch reactor while maintaining the reaction temperature at 0°C. When GC monitoring indicates the reaction is complete, 1N HCl is added, and the mixture is worked up as described above.

[0103] Example 4: Synthesis of 2-oxo-4-methylthiobutanoic acid isopropyl ester (kilogram scale synthesis) Step 1, Grignard Reaction. In a 20 L laboratory reactor, vinylmagnesium chloride (1.6 M in THF, 7 L) was added dropwise over 1 h to a stirred solution of diisopropyl oxalate (1.7 kg, 10 mol) in anhydrous MTBE (3.4 L) at -30 to -20 °C. Gas chromatography showed the vinyl addition was complete, and the reaction mixture was quenched by adding 1 L of saturated aqueous NH4Cl at room temperature. The organic phase was separated and washed with 500 mL of water, and the aqueous phase was back-extracted with 400 mL of MTBE. These MTBE extracts were combined to give 2-oxo-3-butenoic acid isopropyl ester in >90% conversion, which was used directly in the next step without further purification or distillation.

[0104] Step 2, Thiolation: The MTBE extract from Step 1 was cooled to 0 °C in a reactor and treated with triethylamine (10 mL). MeSH gas was generated in situ by reacting a solution of CHSNa (1.0 equiv.; 20% aqueous solution) with HSO (2 equiv.) at 50 °C for 30 min. The generated CHSH gas was bubbled into the stirred reaction solution at 0 °C, and stirring was continued at 0 °C. GC monitoring confirmed that the intermediate was a 2-oxo- Upon indicating conversion of the 2-oxo-4-methylthiobutanoic acid isopropyl ester to 2-oxo-4-methylthiobutanoic acid, 780 mL of 1N HCl was added to the reactor to quench the reaction mixture. The organic layer was separated from the aqueous phase and washed with 500 mL of water, and the aqueous phase was extracted with 650 mL of MTBE (2×). The combined organic extracts were concentrated by evaporation under reduced pressure, and the product was purified by distillation under reduced pressure to give 1021 g (55%) of 2-oxo-4-methylthiobutanoic acid isopropyl ester as a colorless oil. 13 C NMR (100 MHz, CDCl3) δ(ppm) 193.21, 160.25, 70.95, 39.33, 27.32, 21.63, 15.74 (Figure 2A); 1 HNMR (400 MHz, CDCl 3)δ 5.12 (hept, J = 6.2 Hz, 1 H), 3.13 (t, J = 7.2 Hz, 2 H), 2.76 (t, J = 7.2 Hz, 2 H), 2.11 (s, 3 H), 1.33 (d, J = 6.3 Hz, 6 H) (Figure 2B).

[0105] Example 5: Synthesis of 2-hydroxy-4-methylthiobutanoic acid isopropyl ester (HMBi) [ka]

[0106] To a solution of 2-oxo-4-methylthiobutanoic acid isopropyl ester (1 kg, 5.25 mol) in methanol (2 L) in a 5 L reactor at 0-5 °C, NaBH (99 g, 2.6 mol) was added in several portions. The resulting reaction mixture was maintained at 0-5 °C and stirred for 1 h. The reaction mixture was washed with saturated aqueous NH Cl (500 mL). The organic phase was separated, the solvent was removed by distillation under reduced pressure, and the crude product was purified by distillation to give HMBi (859 g, 85% yield, 97% monomeric ester) as a pale yellow oil. 13 CNM R (100 MHz, CDCl3) δ (ppm) 174.52, 69.85, 69.34, 33.76, 29.69, 21.87, 21.83, 15.60 (Fig. 3A ); 1 HNMR (400 MHz, CDCl3)δ 5.08 (hept, J = 6.3 Hz, 1 H), 4.24 (dd, J = 7.9, 3.8 Hz, 1 H), 2 .97 (br, 1 H), 2.67-2.55 (m, 2 H), 2.10-2.01 (m, 4 H), 1.93-1.84 (m, 1 H), 1.27 (d, J = 1.9 Hz, 3 H), 1.26 (d, J = 2.2 Hz, 3 H) (Figure 3B).

[0107] An alternative method for the synthesis of 2-hydroxy-4-(methylthio)butanoic acid isopropyl ester (HMBi) from 2-oxo-4-methylthiobutanoic acid isopropyl ester (OMBi) [ka]

[0108] A variety of reactants and conditions were screened for the production of HMBi from 2-oxo-4-methylthiobutanoic acid isopropyl ester, including NaBH4, transition metal-catalyzed hydrogenation, and keto reduction. Several reaction temperatures, times, reactants, and solvents were tested. The conversion to product and the yield of isolated product for each combination of conditions were measured, and the results are shown in Table 5. [Table 5] [1] Formula (I): [ka] (In the formula, R 1 is C 1~4 is alkyl, R 2 is C 1~8 Alkyl or C 4~7 is cycloalkyl, R 3 and R 4 are each independently selected from H, methyl, and ethyl. A method for producing a compound of the formula Formula (IV): [ka] with a compound of formula (A): [ka] (wherein X is Br or Cl) by coupling with a vinyl Grignard reagent of formula (III): [ka] and forming a compound of converting said compound of formula (III) to said compound of formula (I); The method comprising: [2]R 1 The method according to [1], wherein [3] Each R 2The method according to [1] or [2], wherein is selected from methyl, ethyl, and isopropyl. [4] Each R 2 The method according to [3], wherein [5]R 3 and R 4 The method according to any one of [1] to [4], wherein each of [6] The compound of formula (I) is represented by formula (IA): [ka] The method according to [1], wherein the compound is [7] The compound of formula (III) is represented by formula (III-A): [ka] The method according to [1], wherein the compound is [8] The method according to any one of [1] to [7], wherein the vinyl Grignard reagent of the formula (A) is vinyl-MgCl. [9] The method according to any one of [1] to [7], wherein X is Cl.

[10] The method according to [9], wherein the coupling is carried out in the presence of a salt additive such as LiCl or ZnCl2.

[11] The method according to any one of [1] to

[10] , wherein the coupling comprises mixing the compound of formula (IV) with about 0.8 to about 2.0 molar equivalents, or about 1.0 to about 1.75 molar equivalents, or about 1.0 to about 1.5 molar equivalents, or about 1.2 to about 1.75 molar equivalents, or about 1.4 to about 1.6 molar equivalents, or about 1.5 molar equivalents of the vinyl Grignard reagent of formula (A).

[12] The method according to any one of [1] to

[11] , wherein the coupling is carried out at a temperature in the range of about −80° C. to about 10° C., or about −80° C. to about −70° C., or about −50° C. to about 10° C., or about −40° C. to about 5° C., or about −50° C. to about −20° C., or about −30° C. to about −20° C., or at a temperature of about −78° C., or about −20° C., or about 0° C.

[13] The method according to any one of [1] to

[12] , wherein the coupling is carried out in an aprotic solvent.

[14] The method of

[13] , wherein the aprotic solvent is an ether such as MTBE, THF, or Et2O, optionally mixed with a non-polar solvent such as heptane or hexane.

[15] The method of

[14] , wherein the aprotic solvent is MTBE or THF, optionally mixed with heptane.

[16] The method according to any one of [1] to

[15] , wherein the concentration of the coupling reaction is about 0.25 M to about 1.3 M (the number of moles of the compound of formula (IV) per liter of reaction solvent), or about 0.4 M to about 1.1 M, or about 0.4 M to about 0.5 M, or about 0.9 M to about 1.0 M, or about 0.5 M, or about 1 M.

[17] By the coupling, the compound of formula (III) and the compound of formula (III-Z): [ka] wherein the mixture has a ratio of (III):(III-Z) of at least 5:1, or at least 6:1, or at least 7:1, or at least 8:1, or at least 9:1, or at least 10:1, or at least 15:1, or at least 20:1.

[18] The conversion of the compound of formula (III) to the compound of formula (I) is carried out by reacting a compound of formula (B) or formula (C): R 1 -SH (B) R 1 -S - M + (C) (In the formula, M + is a metal cation) The compound of formula (III) is thiolated with a thiolating agent to obtain a compound of formula (II): [ka] and forming a compound of reducing said compound of formula (II) to form said compound of formula (I); The method according to any one of [1] to

[17] , comprising:

[19] The method according to

[18] , wherein the thiolation is carried out using a thiolation agent of formula (B) in the presence of an additive.

[20] The additive is an amine base such as triethylamine, diethylamine, pentylamine, or hexylamine; phosphines such as dimethylphenylphosphine (DMPP) or tris(2-carboxyethyl)phosphine (TCEP); basic salts such as NaHCO3 or Na2CO3, a Lewis acid such as scandium(III) triflate or anhydrous cerium(III) chloride, or N-heterocyclic carbene (NHC) complexes such as Au-NHC complexes The method according to

[19] ,

[21] The method according to

[19] , wherein the additive is triethylamine.

[22] The method according to any one of

[18] to

[21] , further comprising generating a thiolation agent of the formula (B) from a thiolation agent of the formula (C).

[23] The method according to

[22] , wherein the generating is carried out in the presence of an acid catalyst.

[24] The method according to

[23] , wherein the acid catalyst is acetic acid, p-toluenesulfonic acid, or H2SO4.

[25] The method according to any one of

[22] to

[24] , wherein the thiolation is carried out at a temperature in the range of about −40° C. to about 10° C., or about −35° C. to about 5° C., or about −30° C. to about −20° C., or at about 0° C.

[26] The method according to any one of

[18] to

[21] , wherein the thiolation agent is represented by formula (C), and the thiolation is carried out at a temperature ranging from about −80° C. to about 35° C., or from about 15° C. to about 35° C.

[27] M + Na + or K +The method according to any one of

[18] to

[26] , wherein

[28] The method according to any one of

[18] to

[27] , comprising extracting the compound of formula (III) into an organic solvent to form an extract of formula (III), and thiolating the compound of formula (III) comprises adding the thiolating agent to the extract of formula (III).

[29] The method according to any one of

[18] to

[28] , wherein the reduction of the compound of formula (II) is carried out in the presence of a reducing agent selected from NaBH4, LiBH4, and Al(O-iPr)3 / iPrOH.

[30] The method according to

[29] , wherein the reducing agent is NaBH4.

[31] Reduction is (a) in an alcoholic solvent such as methanol, ethanol, or isopropanol, and / or (b) using about 0.25 to about 1.0 molar equivalents of a reducing agent, and / or (c) at a temperature in the range of about -10°C to about 30°C, or at about 0°C, if the reducing agent is not Al(O-iPr)3 / iPrOH, or at a temperature in the range of about 50°C to about 90°C, or at about 80°C, if the reducing agent is Al(O-iPr)3 / iPrOH. The method according to any one of

[18] to

[30] ,

[32] The method according to any one of

[18] to

[31] , wherein the thiolation comprises extracting the compound of formula (II) into an organic solvent to form an extract of formula (II), and the reduction comprises adding the reducing agent to the extract of formula (II).

[33] Oxalyl chloride R 2 The method according to any one of [1] to

[32] , further comprising esterifying with —OH to form the compound of formula (IV).

[34] The method of

[33] , wherein the esterifying is carried out in the presence of at least one amine base, such as N,N-dimethylpyridine, pyridine, or triethylamine.

[35] The method according to

[33] or

[34] , wherein the esterification is carried out at a temperature ranging from about −5° C. to about 30° C.

[36] In the presence of an acid catalyst and an optional dehydrating agent such as azeotropic water removal, molecular sieves, or a combination thereof, R 2 The method according to any one of [1] to

[33] , further comprising esterifying oxalic acid with —OH to form the compound of formula (IV).

[37] The method of

[36] , wherein the acid catalyst is selected from p-TsOH; H2SO4; macroporous sulfonic acid resin catalysts such as Amberlyst®-15, Dowex®, or M32; silicoaluminates; phosphoric acid; boronic acid; acetyl chloride; and acids with a pKa of less than 3.

[38] The method according to

[36] , wherein the acid catalyst is p-TsOH or H2SO4.

[39] The method according to

[36] , wherein the acid catalyst is about 0.01 to about 0.1 molar equivalents, or about 0.025 to about 0.05 molar equivalents of p-TsOH, or about 1 to about 3 molar equivalents, or about 2 molar equivalents of H2SO4.

[40] The method according to any one of

[36] to

[39] , wherein the esterification is carried out at the reflux temperature of the reaction solvent.

[41] The method according to any one of

[33] to

[40] , wherein the esterification is carried out in a reaction solvent selected from toluene, CHCl3, and isopropanol.

[42] Formula (I): [ka] (In the formula, R 1 is C 1~4 is alkyl, R 2 is C 1~8 Alkyl or C 4~7 is cycloalkyl, R 3 and R 4 are each independently selected from H, methyl, and ethyl. A method for producing a compound of the formula Formula (II): [ka] with a reducing agent to form the compound of formula (I).

[43] R 1

[42] The method according to

[42] , wherein

[44] Each R 2 The method according to

[42] or

[43] , wherein is selected from methyl, ethyl, and isopropyl.

[45] Each R 2

[44] The method according to

[44] , wherein

[46] R 3 and R 4 The method according to any one of

[42] to

[45] , wherein each of

[47] The compound of formula (I) is represented by formula (IA): [ka] The method according to

[42] , wherein the compound is

[48] ​​The method according to any one of

[42] to

[47] , wherein the reducing agent is selected from NaBH4, LiBH4, and Al(O-iPr)3 / iPrOH.

[49] The method according to

[48] , wherein the reducing agent is NaBH4.

[50] To give back (a) in an alcoholic solvent such as methanol, ethanol, or isopropanol, and / or (b) using about 0.25 to about 1.0 molar equivalents of a reducing agent, and / or (c) at a temperature in the range of about -10°C to about 30°C, or at about 0°C, if the reducing agent is not Al(O-iPr)3 / iPrOH, or at a temperature in the range of about 50°C to about 90°C, or at about 80°C, if the reducing agent is Al(O-iPr)3 / iPrOH. The method according to any one of

[42] to

[49] ,

[51] Formula (III): [ka] (In the formula, R 3 and R 4 are each independently selected from H, methyl, and ethyl. of formula (B) or formula (C): R 1 -SH (B) R 1 -S - M + (C) (In the formula, M + is a metal cation) The method according to any one of

[42] to

[49] , further comprising thiolating the compound of formula (II) with a thiolating agent of the formula (II).

[52] The compound of formula (III) is represented by formula (III-A): [ka] The method according to

[51] , wherein the compound is

[53] Formula (IA): [ka] A method for producing a compound of the formula esterifying oxalic acid with isopropanol to form diisopropyl oxalate; Diisopropyl oxalate is coupled with vinylmagnesium bromide to give formula (III-A): [ka] and forming a compound of The compound of formula (III-A) is thiolated with CH3SH to obtain the compound of formula (II-A): [ka] and forming a compound of reducing said compound of formula (II-A) to form said compound of formula (IA); The method comprising:

[54] The method according to any one of [1] to

[53] , which provides the compound of formula (I) or formula (IA) in a purity of at least about 95% by GC, HPLC, and / or weight.

[55] The method according to any one of [1] to

[54] , which provides a crude compound of formula (I) or formula (IA) having a purity of at least about 95%, or at least about 96%, or at least about 97%, or at least about 98% by weight, GC, and / or HPLC, wherein the crude compound is unpurified or purified only by fractional distillation.

[56] The method according to any one of [1] to

[55] , which provides a crude compound of formula (I) or formula (IA) that is substantially in monomeric form or contains less than about 5% by weight, or less than about 3% by weight, of dimeric and / or oligomeric compounds, and which is unpurified or purified only by fractional distillation.

[57] A compound of formula (I) or formula (IA) produced by the method according to any one of [1] to

[56] .

[58] An animal feed composition comprising the compound according to

[57] .

[59] The animal feed composition according to

[58] , which is a cattle feed composition such as a dairy cattle feed composition, or an additive for cattle feed such as dairy cattle feed.

[60] The animal feed composition according to

[59] , which is a dairy cattle feed composition.

[61] The animal feed composition according to any one of

[58] to

[60] , which is an animal feed or an animal feed additive.

[62] The animal feed composition of

[61] , wherein the animal feed additive is in liquid or solid form, the liquid form comprising the compound and optionally a liquid carrier, and the solid form comprising the compound mixed with a solid carrier, optionally the solid carrier being silica (silicon dioxide), and optionally the ratio of the compound to the solid carrier is from about 5:1 to about 1:5, or about 3:2.

[63] A method for supplying biologically available methionine to dairy cows, the method comprising administering to the cows the compound described in

[57] or the animal feed composition described in any one of

[58] to

[62] .

[64] A method for providing at least about 50% bioavailable methionine to a dairy cow, the method comprising administering to the cow the compound described in

[57] or the animal feed composition described in any one of

[58] to

[62] .

[65] A method for improving milk obtained from dairy cows, the method comprising feeding the cows the compound described in

[57] or the animal feed composition described in any one of

[58] to

[62] .

[66] The method of

[65] , wherein the improvement of the milk comprises increasing the protein content in the milk.

[67] The method of

[65] , wherein the improvement of the milk comprises increasing the fat content in the milk.

[68] The compound according to

[57] or the animal feed composition according to any one of

[58] to

[62] for use in a method for improving milk obtained from dairy cows.

[69] The compound or composition for use according to

[68] , wherein the improvement of the milk comprises an increase in the protein content in the milk.

[70] The compound or composition for use according to

[68] , wherein the improvement in the milk comprises an increase in the fat content in the milk.

[71] A method for improving the condition of cattle, comprising feeding the cattle with the compound described in

[57] or the animal feed composition described in any one of

[58] to

[62] .

[72] The method of

[71] , wherein the improvement in the condition of the cow includes improvement in fertility.

[73] The method described in

[71] , wherein the improvement in the condition of the cow includes improvement in liver function.

[74] The method of

[71] , wherein the improvement in the condition of the cow comprises an increase in energy.

[75] The method according to any one of

[63] to

[67] or

[71] to

[74] , wherein administering or providing comprises feeding the animal feed composition to the cattle.

[76] The compound according to

[57] or the animal feed composition according to any one of

[58] to

[62] for use in a method for improving the condition of cattle.

[77] The compound or composition for use according to

[76] , wherein the improvement of the condition of the cow comprises improvement of fertility.

[78] The compound or composition for use according to

[76] , wherein the improvement in the condition of the cow comprises improvement in liver function.

[79] The compound or composition for use according to

[76] , wherein the improvement in the condition of the cow comprises an increase in energy.

[80] A compound which is isopropyl 2-oxobut-3-enoate.

Claims

[Claim 1] Formula (I): 【Chemistry 1】 (In the formula, R １ is C １～４ is alkyl, R ２ is C １～８ Alkyl or C ４～７ is cycloalkyl, R ３ and R ４ are each independently selected from H, methyl, and ethyl. A method for producing a compound of the formula a) Formula (IV): 【Chemistry 2】 with a compound of formula (A): 【Transformation 3】 wherein X is Br or Cl. by coupling with a vinyl Grignard reagent of formula (III): 【Chemistry 4】 forming a compound of converting said compound of formula (III) to said compound of formula (I), The conversion of the compound of formula (III) to the compound of formula (I) can occur directly by a reduction reaction followed by a thiolation reaction, or by a thiolation reaction followed by a reduction reaction; or b) Formula (II): 【Transformation 5】 The compound of ４ , LiBH ４ , and Al(O-iPr) ３ / iPrOH to form a compound of formula (I), The method.

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