Dehydration and decomposition of alpha- and beta-dihydroxycarbonyl compounds to lactic acid and other products

Abstract

A process for synthesizing degradation products from starting substrates having a carbonyl functional group (C═O) with hydroxy substitution at the carbon atoms α and β relative to the carbonyl functional group is disclosed. In one embodiment, a dicarbonyl intermediate is produced by dehydrating an α-, β-dihydroxycarboxylic acid or carboxylate, converting the α-hydroxy group to a second carbonyl group and removing the β-hydroxy group. Decomposition of this dicarbonyl intermediate produces degradation products that preserve the first and second carbonyl groups. Additional products may be produced by hydrogenating one or both of (i) the degradation product and (ii) the second degradation product, which are produced by cleaving the carbon-carbon bond of the dicarbonyl intermediate.

Description

[Technical Field]

[0001] FIELD OF THE INVENTION

[01] The present invention relates to a method for synthesizing degradation products, including pyruvate and glyceraldehyde, which are precursors to many valuable end products, in which the degradation products and end products have fewer carbon atoms than the starting α-,β-dihydroxycarbonyl compounds (including α-,β-dihydroxycarboxylic acids and carboxylates, such as those obtained from glucose). [Background technology]

[0002] Background technology

[02] The depletion of fossil fuels has largely motivated the search for alternative sources of petroleum-based carbon for use in the production of so-called "platform" molecules with fewer carbon atoms, including propylene glycol and other carbon-3 (C3) products. Biomass is now seen as a promising alternative from which many of these well-known high-value petroleum-based chemicals can be derived; however, developing sustainable technologies for producing these chemicals from renewable resources remains a significant challenge. In recent years, the biodiesel industry has produced large amounts of crude glycerol as a by-product of refining triglycerides in vegetable oils and animal fats. This glycerol can also serve as a feedstock for the production of lower-carbon, high-value chemicals, such as propylene glycol. However, the processing costs required to sufficiently refine glycerol for this purpose are substantial, and the biodiesel industry relies heavily on tax credits and other forms of government subsidies to remain viable. Summary of the Invention [Problem to be solved by the invention]

[0003]

[03] The current state of the art would provide significant benefits through pathways for the synthesis of high-value intermediates such as pyruvate and glyceraldehyde from readily available or obtainable substrates, particularly those derived from renewable carbohydrate sources, and / or downstream conversion products such as lactate, glycerol, propylene glycol, etc. [Means for solving the problem]

[0004] Summary of the Invention

[04] Aspects of the present invention relate to the discovery of synthetic methods that can utilize substrates such as gluconic acid and glucaric acid, which are readily obtained by oxidizing glucose. These substrates tend to exhibit greater stability under high-temperature conditions than their precursor aldehydes (e.g., glucose), thereby enabling improved reaction selectivity and yield along a desired reaction sequence to obtain one or more defined products. Product losses due to undesired side reactions are therefore reduced. Products of particular interest include "cracked" products, which are formed by cleavage of carbon-carbon bonds and therefore contain fewer carbon atoms than the substrate used. Obtaining suitable substrates by oxidizing aldehyde precursors to carboxylates is simple and inexpensive, typically requiring only air as the oxidizing agent. A particular embodiment involves the ability of substrates containing carboxylate anions to undergo a series of reaction steps in solution leading to the production of desirable three carbon atom degradation products such as pyruvate and glyceraldehyde, which can be further converted under the same reaction conditions (e.g., hydrogenation / reduction) to desirable end products such as lactic acid, glycerol, and even propylene glycol (1,2-propanediol).

[0005]

[05] Certain embodiments relate to synthetic pathways that utilize a decomposition step following the generation of a dicarbonyl intermediate from an α-,β-dihydroxycarbonyl compound starting material. Decomposition can be facilitated by the use of a decomposition catalyst under the reaction conditions described herein. Decomposition products with fewer carbon atoms include, for example, 3-carbon compounds, which can be synthesized from any 4-, 5-, or 6-carbon substrate or starting compound, such as those described above. Substrates of this type can generally produce pyruvate as a decomposition product, for example. More specific embodiments relate to the discovery that such synthetic pathways, or individual reaction steps of such pathways, can be carried out nonenzymatically, i.e., without the use of enzymes (e.g., polypeptides) in the reaction mixture. Nonenzymatic methods, such as those described herein that use only one or more chemical catalysts distinct from biological catalysts, have the advantage that the range of possible reaction conditions can be expanded, for example, to temperature and / or pH conditions that would be detrimental to biological agents (e.g., that would denature proteins such as enzymes), yet still provide high productivity of the desired intermediate and / or end product. Another advantage may be achieved by reduced operating costs, particularly the reduced costs associated with separating a heterogeneous or homogeneous chemical catalyst compared to the costs associated with separating an enzyme from a product. According to some embodiments, at least one of the synthetic steps described herein, (i) dehydrating a starting compound to produce a dicarbonyl intermediate, (ii) decomposing the dicarbonyl intermediate to produce a degradation product, (iii) hydrogenating the degradation product to produce an end product, and (iv) converting a second degradation product to an additional amount of the end product, is a non-enzymatic reaction step (i.e., does not use enzyme catalysis).Preferably, at least two of (i), (ii), (iii), and (iv) are non-enzymatic reaction steps, more preferably, at least three of (i), (ii), (iii), and (iv) are non-enzymatic reaction steps, and even more preferably, (i), (ii), (iii), and (iv) are all non-enzymatic reaction steps.

[0006]

[06] An embodiment of the present invention relates to a method for synthesizing degradation products having fewer carbon atoms than a starting compound. The starting compound or substrate contains a carbonyl functional group (C=O) with hydroxy substitutions at the carbon atoms alpha (α) and beta (β) relative to the carbonyl functional group. In one reaction step, the starting compound, i.e., an α-,β-dihydroxycarbonyl compound (i.e., a general class of compounds encompassing α-,β-dihydroxycarboxylic acids and carboxylates), undergoes dehydration, converting the α-hydroxy group to a second carbonyl group (adjacent to the carbonyl group of the starting compound) and removing the β-hydroxy group to produce a dicarbonyl intermediate. The dicarbonyl intermediate then decomposes to produce degradation products that are themselves dicarbonyl compounds but have fewer carbon atoms than the dicarbonyl intermediate, preserving the first and second carbonyl groups. Typically, this decomposition produces a second degradation product, such as an aldehyde or carboxylate, that is distinct from the degradation (dicarbonyl) product. In many cases, for substrates with six carbon atoms, both the decomposition (dicarbonyl) product and the secondary decomposition (e.g., aldehyde or carboxylate) product can be a three-carbon product, such as glyceraldehyde or 2-hydroxy-3-oxopropanoic acid. For substrates with five carbon atoms, the decomposition (dicarbonyl) product can be a three-carbon product, and the secondary decomposition (e.g., aldehyde or carboxylate) product can be a two-carbon product, such as 2-hydroxyacetaldehyde or 2-oxoacetic acid. For substrates with four carbon atoms, the decomposition (dicarbonyl) product can be a three-carbon product, and the secondary decomposition (e.g., aldehyde or carboxylate) product can be a one-carbon product, such as formaldehyde or formic acid.

[0007]

[07] One or both of the degradation products and secondary degradation products that may be present in the reaction environment can also be further converted to hydrogenated end products, for example, by hydrogenation / reduction under reducing conditions (e.g., high hydrogen partial pressure). Such hydrogenated end products can include lactic acid when the degradation (dicarbonyl) product is pyruvate, or glycerol or glyceric acid when the secondary degradation (e.g., aldehyde or carboxylate) product is glyceraldehyde or 2-hydroxy-3-oxopropanoic acid, respectively. Another useful end product can include lactic acid, which is produced from glyceraldehyde via a reaction involving 1,2-hydrogen transfer or hydrogen rearrangement (Cannizzaro reaction).

[0008]

[08] These and other aspects, embodiments, and attendant advantages will become apparent from the following detailed description. [Brief explanation of the drawings]

[0009] BRIEF DESCRIPTION OF THE DRAWINGS [Figure 1]

[09] Illustrates a general reaction scheme including steps for synthesizing degradation products and final products according to the synthetic methods described herein. [Figure 2]

[10] This illustrates a specific reaction mechanism using gluconic acid as a starting material or substrate. DETAILED DESCRIPTION OF THE INVENTION

[0010]

[11] It should be understood that the drawings depict embodiments of the invention for the purpose of aiding in understanding the underlying principles and chemistry of the reactions involved, but are not intended to limit the scope of the invention as defined in the appended claims. It will be apparent to one of skill in the art with knowledge of this disclosure that synthetic methods according to various other embodiments of the invention will utilize specific reagents and reaction conditions determined, at least in part, for a particular purpose.

[0011] Detailed Description of the Embodiments

[12] As used herein, the term "substrate" or alternatively "starting compound" refers to an initial compound that is subjected to one or, preferably, a series of conversion steps, such as "dehydration," "cracking," and optionally "hydrogenation," to produce one or more degradation products and / or end products. These conversion steps do not exclude the use of preceding conversion steps, e.g., conversion steps performed under the same reaction conditions (e.g., in the same reactor) or different reaction conditions (e.g., in a separate reactor) than those used to produce the degradation product(s) and / or end product(s). Such preceding conversion steps can include converting readily available precursors, such as glucose, to the starting compounds gluconic acid or glucaric acid, such as by oxidation. Similarly, steps performed "to produce a degradation product" or "to produce an end product" do not exclude the use of subsequent conversion steps, e.g., conversion steps performed under the same reaction conditions (e.g., in the same reactor) or different reaction conditions (e.g., in a separate reactor) than those used to produce the degradation product(s) and / or end product(s), aimed at obtaining one or more other desired end products. For example, the hydrogenated end product lactic acid can be further converted to propylene glycol or acrylic acid, and the hydrogenated end product glyceric acid can be further converted to glycerol.

[0012]

[13] The terms "mol%" and "wt%" are used to denote amounts or concentrations in the sense of percent by mole and percent by weight, respectively. Product yields given in terms of "mol%" refer to the number of moles of a given product (e.g., a degradation product such as pyruvate) obtained based on the number of moles of substrate used (introduced or fed to the reactor).

[0013]

[14] The term "alkyl," used alone or in combination with other moieties, e.g., "alkoxy," "alkoxyalkyl," "hydroxyalkyl," "carboxyalkyl," "alkanoyl," and "alkanoylalkyl," refers to a hydrocarbon moiety derived from an alkane. Thus, "alkyl" when used alone includes "methyl" (CH-), "ethyl" (CH-), etc. When used in combination, the alkyl portion of an "alkoxy" moiety is attached at its terminus to the rest of the molecule through an oxygen linkage -O-, as in, for example, "methoxy" (CH-O-) and "ethoxy" (CH-O-) (which terms are encompassed by "alkoxy"). The alkyl portion of an "alkanoyl" moiety is attached at its terminus to the rest of the molecule via a carbonyl bond -(C=O)-, with "methanoyl" (HC=O-) representing a terminal aldehyde moiety, "ethanoyl" (CH3-(C=O)-) representing a methyl attached via a carbonyl bond, and so forth (these terms are encompassed by "alkanoyl").

[0014]

[15] The term "hydroxy" refers to an -OH moiety, and the term "carboxy" refers to an -(C=O)OH moiety. The term "hydroxyalkyl" refers to a hydroxy group whose terminal end is attached to the remainder of the molecule through a divalent alkyl moiety, as in "hydroxymethyl" (HO-CH2-), "hydroxyethyl" (HO-C2H5-), etc. (these terms are encompassed by "hydroxyalkyl"). The term "carboxyalkyl" refers to a carboxy group whose terminal end is attached to the remainder of the molecule through a divalent alkyl moiety, as in "carboxymethyl" (HO-(C=O)-CH2-) and "carboxyethyl" (HO-(C=O)-C2H5-) (these terms are encompassed by "carboxyalkyl"). The term "alkoxyalkyl" includes both terminal alkoxy moieties (i.e., attached to the terminal end of the moiety) and intervening divalent alkyl moieties (through which the "alkoxy" is attached to the remainder of the molecule), as defined above by the designation "alkoxy." Thus, "alkoxyalkyl" includes "methoxymethyl" (CH3-O-CH2-), "methoxyethyl" (CH3-O-C2H4-), "ethoxymethyl" (C2H5-O-CH2-), "ethoxyethyl" (C2H5-O-C2H4-), and the like. The term "alkanoylalkyl" includes both the terminal alkanoyl portion (i.e., attached to the end of the moiety) designated by the "alkanoyl" designation defined above, and the intervening divalent alkyl portion (through which the "alkanoyl" is attached to the remainder of the molecule). Thus, "alkanoylalkyl" includes "methanoylmethyl" (H(C=O)-CH2-), "methanoylethyl" (H(C=O)-C2H4-), "ethanoylmethyl" (CH3-(C=O)-CH2-), "ethanoylethyl" (CH3-(C=O)-C2H4-), and the like.

[0015]

[16] The term "optionally substituted" with respect to "alkyl," or with respect to either the terminal or intervening alkyl portions of the moieties defined above, is meant to encompass replacement of hydrogen substituents of one or more carbon-hydrogen bonds of the alkyl or alkyl portion with the specified substituent. In the case of hydroxy (-OH) or methyl (-CH) substituents, one, two, or three hydrogen substituents of the carbon-hydrogen bonds of the terminal alkyl carbon atom may be replaced with -OH and / or -CH substituents, respectively, and one or two hydrogen substituents of the carbon-hydrogen bonds of the intervening (alkylene)alkyl carbon atoms may be replaced with -OH and / or -CH substituents, respectively. For example, in the case of a terminal alkyl portion, the terminal carbon atom may be replaced with two -CH substituents to form a terminal isopropyl moiety or three -CH substituents to form a terminal t-butyl moiety. In the case of an intervening alkyl moiety, or an intervening carbon atom of a terminal alkyl moiety, one or two hydrogen substituents of the carbon-hydrogen bonds of the alkylene carbon atom may be replaced with -CH3 substituents to give the corresponding methyl- or dimethyl-substituted derivatives. Similar replacement of a terminal alkyl carbon atom or an intervening alkyl carbon atom with one or more -OH substituents is also understood from this description. In the case of a carbonyl (=O) substituent, the hydrogen substituents of two carbon-hydrogen bonds of either the terminal alkyl carbon atom or the intervening (alkylene) alkyl carbon atom may be replaced with =O to give a terminal aldehyde moiety (or group) or a carbonyl moiety (or group), respectively.

[0016]

[17] It is recognized that there may be overlap in the definitions of moieties, given the possible moieties and the manner in which they may be substituted. For example, "methanoyl" and a terminal "methyl" substituted with =0 both represent a terminal aldehyde moiety (or group). However, specific moieties are mentioned to emphasize their definitive inclusion in a given compound. In addition, when an "alkyl" or "alkyl moiety" is further defined in terms of its corresponding number of carbon atoms (e.g., an alkyl or alkyl moiety "having 1 to 5 carbon atoms"), the optional -CH3 substituent (if present) is not included in this carbon atom count. That is, the phrase "having 1 to 5 carbon atoms" and other phrases defining the number of alkyl carbon atoms refer to the number of backbone alkyl carbon atoms, which may be further substituted with -CH3 or other substituents according to the specific definition given.

[0017]

[18] Carboxylic acid compounds encompass their corresponding salt forms. For starting compounds or substrates having a carboxylic acid functional group, the salt form is typically used in the aqueous solution for carrying out the synthetic methods described herein. Corresponding salt forms of carboxylic acids include, for example, alkali metal salts (e.g., sodium salt form), alkaline earth metal salts (e.g., calcium salt form), and ammonium salts. Thus, compounds such as "gluconic acid," "glucaric acid," "tartaric acid," "pyruvic acid," "lactic acid," "2-hydroxy-3-oxopropanoic acid," and "glyceric acid" are meant to encompass salt forms such as "gluconate," "glucarate," "tartrate," "pyruvate," "lactate," "2-hydroxy-3-oxopropanoate," and "glycerate." Similarly, the general and specific structures illustrating carboxylic acid compounds are both meant to encompass their salt or ionized forms, so that, for example, if gluconic acid is shown in a structure in which its carboxyl group is not ionized, it is also meant to encompass a structure in which its carboxyl group is ionized, and vice versa. The equivalent structures of this compound, with the unionized and ionized carboxyl groups, are shown below.

change

[0018]

[19] Compounds can have one or more asymmetric centers, and structures are illustrated without regard to specific stereochemistry. Similarly, it is understood that reactions described with substrates such as "gluconic acid," "glucaric acid," and "erythronic acid," which, according to their nomenclature, are designated with a specific stereochemistry, can be carried out in an analogous manner with the respective non-stereospecific substrates "2,3,4,5,6-pentahydroxyhexanoic acid," "2,3,4,5-tetrahydroxyhexanedioic acid," and "2,3,4-trihydroxybutanoic acid," as well as with any stereoisomer of such compounds. Thus, unless otherwise specified, "gluconic acid" is intended to encompass "gluconic acid and its stereoisomers," as well as with other compounds designated with a specific stereochemistry. The generic and specific compounds described herein can be used or obtained in the form of pure or purified (enriched) optical isomers, or otherwise in the form of racemic mixtures thereof. When optically active substrates or starting compounds are used, the synthetic methods described herein can be used to produce optically active products, as will be understood by those skilled in the art in conjunction with the knowledge gained from this disclosure. If desired, purification of a specific optical isomer or enrichment of one optical isomer relative to the other can be achieved, for example, by treatment with an optically active acid or base to form a diastereomeric salt. Examples of suitable acids are tartaric acid, diacetyltartaric acid, dibenzoyltartaric acid, ditoluoyltartaric acid, and camphorsulfonic acid. Examples of suitable bases are chiral alkaloids derived from plants. The diastereomeric mixture is then crystallized and separated by liberating the optically active base or acid from the salt. Another process for separating optical isomers involves the use of chiral chromatography columns selected to maximize the separation of the enantiomers. Yet another available method involves synthesizing covalent diastereomeric molecules by reaction with optically pure acids or optically pure isocyanates in activated form.The synthesized diastereomers can be separated by conventional means such as chromatography, distillation, crystallization, or sublimation, and then hydrolyzed to deliver the enantiomerically pure compound.

[0019]

[20] Figure 1 illustrates a general reaction scheme for synthesizing the degradation products and final products. As shown, the starting materials of general formula I are a wide range of α-,β-dihydroxycarbonyl compounds, which represent a preferred class of compounds, namely, R 1 is hydroxy (—OH), providing a terminal carboxyl group on the left side of the illustrated compound, encompassing α-,β-dihydroxycarboxylates. The starting material of general formula I in FIG. 1 contains an α-hydroxy group substituting the α-carbon atom relative to the depicted carbonyl (C═O) group and a β-hydroxy group substituting the β-carbon atom relative to the carbonyl group. According to the illustrated synthetic scheme, a first step, dehydration (removal of water), removes the β-hydroxy group and forms a site of unsaturation, i.e., a carbon-carbon double bond, between the α- and β-carbon atoms. The resulting ethylenically unsaturated dehydrated compound, designated Compound A, tends to maintain tautomeric equilibrium with the dicarbonyl intermediate, designated as having general formula IIA. Thus, this dehydration step can involve the formation of water by combining the β-hydroxy group with the hydrogen of the α-hydroxy group within the starting compound or substrate of general formula I.

[0020]

[21] The dicarbonyl intermediate compound of general formula IIA can then be decomposed to produce a decomposition product of general formula IIB. As a result of the decomposition, the R 2B The moiety represented by R 2AThe decomposition product will generally have fewer carbon atoms than the dicarbonyl intermediate. This decomposition product can then be optionally hydrogenated to produce a final product, where the corresponding hydrogenated final product has the general formula IIIB, as shown in FIG. 1. The decomposition product formed by decomposition also forms a second decomposition product having the general formula IIC, and thus an aldehyde group. This second decomposition product may contain other functional groups, such as a carboxylic acid functional group, attached to the R bond to the aldehyde functional group, depending on the substrate or starting compound. 2C or otherwise at the terminal end of this moiety. Secondary decomposition products of this type can be, for example, R 2A is attached via a hydroxy-substituted carbon atom. That is, the starting compound can further include a gamma hydroxy group substituting the carbon atom gamma to the first carbonyl group, such that upon decomposition, in addition to forming a first (dicarbonyl) decomposition product, a second decomposition product having an aldehyde group resulting from cleavage between the beta and gamma carbon atoms of the dicarbonyl intermediate (corresponding to the beta and gamma carbon atoms of the starting compound) is formed. In certain embodiments, R 2A Or at least R 2A ends with: [ka] When R represents a moiety of the second decomposition product having general formula IIC, a second decomposition product of general formula IIC can be produced, in which case the decomposition product will have fewer carbon atoms than both the dicarbonyl intermediate and the substrate. This decomposition product can then optionally be subjected to hydrogenation. Alternatively, the second decomposition product can be further converted (e.g., also by hydrogenation) to produce other desirable compounds, such as those described with respect to the more specific embodiment shown in Figure 2. According to some methods, the R of the second decomposition product having general formula IIC can be 2C The part represented by R2A and this second decomposition product may have one less carbon atom than the moiety represented by R 2A formed from R 2A and the corresponding aldehyde or the corresponding carboxylic acid having the same number of carbon atoms. In this case, the degradation product can be pyruvic acid, which can be hydrogenated to lactic acid. Thus, it can be seen that a synthetic route to lactic acid via the decomposition of a dicarbonyl intermediate to form pyruvic acid can be carried out by using various α-,β-dihydroxycarbonyl compounds as substrates, including α-,β-dihydroxycarboxylic acids and carboxylates having at least four carbon atoms.

[0021]

[22] Thus, a representative method can include not only the production of a decomposition product that is a dicarbonyl compound, but also the hydrogenation of some or all of the decomposition product to produce a final product that not only preserves the first carbonyl group of the starting compound and the dicarbonyl intermediate, but also contains an adjacent hydroxy group generated by hydrogenation of the second carbonyl group of the decomposition product. As the decomposition product of general formula IIB is consumed by hydrogenation, the decomposition reaction proceeds in the forward direction, ultimately shifting the tautomeric equilibrium in this direction to produce additional dicarbonyl compounds from compound A. The rate at which the decomposed (dicarbonyl) product is hydrogenated can be adjusted by the use of an optional decomposition catalyst and reaction conditions, as described herein. The degradation step can produce three-carbon degradation products, such as pyruvic acid, from available starting compounds containing four, five, or six carbon atoms, such as α- and β-dihydroxycarboxylic acids and carboxylates, including erythronic acid (or generally 2,3,4-trihydroxybutanoic acid); 2,3-dihydroxy-4-oxobutanoic acid; tartaric acid; 2,3,4,5-tetrahydroxypentanoic acid; 2,3,4-trihydroxy-5-oxopentanoic acid; 2,3,4-trihydroxypentanedioic acid; gluconic acid (or generally 2,3,4,5,6-pentahydroxyhexanoic acid); 2,3,4,5-tetrahydroxy-6-oxohexanoic acid; and glucaric acid (or generally 2,3,4,5-tetrahydroxyhexanedioic acid). Thus, a typical synthesis method involves converting available C4-C6 substrates, such as readily available carbohydrates, to produce C3 compounds as degradation and final products. In such embodiments, when the substrate is a compound having six carbon atoms (C6 substrate), the second degradation product of the synthesis method is also a C3 compound. For example, the six carbon atom substrates gluconic acid and glucaric acid can each produce pyruvate as a degradation product and lactate as an end product by hydrogenating lactate. In the case of gluconic acid, the second degradation product can be glyceraldehyde, which can be hydrogenated to produce glycerol as an end product.In the case of glucaric acid, the second degradation product can be 2-hydroxy-3-oxopropanoic acid, which can be hydrogenated to produce glyceric acid as the final product.

[0022]

[23] For compounds having the general formula I, IIA, IIB, and IIIB in Figure 1, as well as compounds having the general formula given for compound A, R 1 can be selected from the group consisting of alkyl, alkoxy, alkoxyalkyl, hydroxy, and hydroxyalkyl, where the alkyl and alkyl portions of the alkoxy, alkoxyalkyl, and hydroxyalkyl have 1 to 5 carbon atoms, optionally substituted with one or more substituents selected from the group consisting of -OH, -CH3, and =O (i.e., optionally, hydrogen substituents on the carbon-hydrogen bond may be substituted with one or more substituents as described herein). According to certain embodiments, in each of these compounds, including the starting compound of general formula I, the dicarbonyl intermediate and decomposition product represented by general formulas IIA and IIB, respectively, and / or the final product of general formula IIIB, R 1 can be alkyl (e.g., having 1 to 3 alkyl carbon atoms), thereby providing a terminal ketone functionality in each compound; R 1 can be alkoxy (e.g., having 1 to 3 alkyl carbon atoms), thereby resulting in a terminal ester functionality in each compound; or R 1 can be hydroxy, thereby providing a terminal carboxyl functionality in each compound. Preferably, R 1is hydroxy, thereby making the starting compounds and dicarbonyl intermediates carboxylic acids. For example, as generally described above with respect to terms used herein, the starting compounds, dicarbonyl intermediates, decomposition products, and / or final products can be in the form of a carboxylate (e.g., present in the reaction mixture as a carboxylate), meaning that the compounds include a carboxylate anion and can also be present in salt form (e.g., their corresponding ammonium salt form) in the aqueous reaction mixtures used to practice the synthetic methods described herein.

[0023]

[24] In Figure 1, for compounds having the general formula I and IIA, as well as compounds having the general formula given for compound A, R 2A can be selected from the group consisting of alkyl, alkoxy, alkoxyalkyl, hydroxy, hydroxyalkyl, carboxy, carboxyalkyl, alkanoyl, and alkanoylalkyl, where the alkyl and alkyl portions of the alkoxy, alkoxyalkyl, hydroxyalkyl, carboxyalkyl, alkanoyl, and alkanoylalkyl have 1 to 5 carbon atoms optionally substituted with one or more substituents selected from the group consisting of -OH, -CH3, and =O. According to certain embodiments, R 2A can be selected from the group consisting of alkyl, alkoxy, hydroxy, hydroxyalkyl, carboxy, carboxyalkyl, alkanoyl, and alkanoylalkyl, where the alkyl and alkyl portions of the alkoxy, alkoxyalkyl, hydroxyalkyl, carboxyalkyl, alkanoyl, and alkanoylalkyl have 1 to 3 carbon atoms optionally substituted with one or more -OH and / or one or more -CH3. According to more specific embodiments, R 2Amay be alkyl, carboxy, carboxyalkyl, alkanoyl, or alkanoylalkyl, where the alkyl and alkyl portions of carboxyalkyl, alkanoyl, and alkanoylalkyl have 1 to 3 carbon atoms, optionally substituted with one or more -OH. Specific substrates having 4 to 6 carbon atoms include erythronic acid (or generally 2,3,4-trihydroxybutanoic acid); 2,3-dihydroxy-4-oxobutanoic acid; tartaric acid; 2,3,4,5-tetrahydroxypentanoic acid; 2,3,4-trihydroxy-5-oxopentanoic acid; 2,3,4-trihydroxypentanedioic acid; gluconic acid (or generally 2,3,4,5,6-pentahydroxyhexanoic acid); 2,3,4,5-tetrahydroxy-6-oxohexanoic acid, and glucaric acid (or generally 2,3,4,5-tetrahydroxyhexanedioic acid).

[0024]

[25] In certain substrates with four carbon atoms, R 1 is hydroxy and R 2A If is hydroxymethyl, the starting compound is erythronic acid (or generally 2,3,4-trihydroxybutanoic acid). Therefore, in this case, the decomposition step may produce, in addition to pyruvic acid, a secondary degradation product with one carbon atom, such as formaldehyde. Hydrogenation of this degradation product would then yield lactic acid and methanol, respectively. Table 1 below shows this and other examples of substrates with four and five carbon atoms and their corresponding degradation products, secondary degradation products, and hydrogenation products.

[0025] [Table 1]

[0026] Specific examples of six-carbon substrates and their corresponding decomposition products, secondary decomposition products, and hydrogenation products are described below in relation to substrates of formulas IV and VI, which have specific structures within the scope of formula I.

[0027]

[26] For compounds having general formula IIB and IIIB, R 2B can be selected from the group consisting of hydrogen substituents, alkyl, alkoxy, alkoxyalkyl, hydroxy, hydroxyalkyl, carboxy, carboxyalkyl, alkanoyl, and alkanoylalkyl, where the alkyl and alkyl portions of the alkoxy, alkoxyalkyl, hydroxyalkyl, carboxyalkyl, alkanoyl, and alkanoylalkyl have 1 to 4 carbon atoms optionally substituted with one or more substituents selected from the group consisting of -OH, -CH3, and =O. According to certain embodiments, R 2B can be selected from the group consisting of hydrogen substituents, alkyl, alkoxy, hydroxy, hydroxyalkyl, carboxy, carboxyalkyl, alkanoyl, and alkanoylalkyl, where the alkyl and alkyl portions of alkoxy, alkoxyalkyl, hydroxyalkyl, carboxyalkyl, alkanoyl, and alkanoylalkyl have 1 to 3 carbon atoms optionally substituted with one or more -OH and / or one or more -CH. According to more specific embodiments, R 2B may be a hydrogen substituent, alkyl, carboxy, carboxyalkyl, alkanoyl, or alkanoylalkyl, where the alkyl and alkyl portions of carboxyalkyl, alkanoyl, and alkanoylalkyl have 1 or 2 carbon atoms optionally substituted with one or more -OH. 2B may be an alkyl having 1 to 3 carbon atoms optionally substituted with hydrogen substituents or one or more -OH.

[0028]

[27] From this disclosure, R 1 is hydroxy and R 2B is a hydrogen substituent, the degradation product is pyruvate, which can be hydrogenated to form lactic acid, which can be obtained from a variety of possible α-, β-hydroxycarboxylate substrates, as discussed above.2A Or at least R 2A ends with: [ka] Thus, R of the compound of general formula IIC may be formed when R 2C is R 2A can represent the moiety defined for R, but with at least one less carbon atom. 2C can be selected from the group consisting of hydrogen substituents, alkyl, alkoxy, alkoxyalkyl, hydroxy, hydroxyalkyl, carboxy, carboxyalkyl, alkanoyl, and alkanoylalkyl, where the alkyl and alkyl portions of the alkoxy, alkoxyalkyl, hydroxyalkyl, carboxyalkyl, alkanoyl, and alkanoylalkyl have 1 to 4 carbon atoms optionally substituted with one or more substituents selected from the group consisting of -OH, -CH3, and =O. According to certain embodiments, R 2C can be selected from the group consisting of hydrogen substituents, alkyl, alkoxy, hydroxy, hydroxyalkyl, carboxy, carboxyalkyl, alkanoyl, and alkanoylalkyl, where the alkyl and alkyl portions of alkoxy, alkoxyalkyl, hydroxyalkyl, carboxyalkyl, alkanoyl, and alkanoylalkyl have 1 or 2 carbon atoms optionally substituted with one or more -OH and / or one or more -CH. According to more specific embodiments, R 2C may be an alkyl having 1 or 2 carbon atoms optionally substituted with hydrogen substituents or one or more -OH.

[0029]

[28] In a more specific embodiment, R of the compound of Figure 1 2A The parts are: [ka] whereby the starting compound and the dicarbonyl intermediate compound can be represented by the general formula IV and the general formula VA, respectively: [ka] and the compounds may optionally be in their respective salt forms as described above. For these compounds, R 1 can be as described above. R 3A can be selected from the group consisting of hydrogen substituents, alkoxy, hydroxy, and carboxy, where the alkyl portion of the alkoxy has 1 to 5 carbon atoms, optionally substituted with one or more substituents selected from the group consisting of OH, CH3, and =O. Preferably, R 3A is a hydrogen substituent, methyl, methoxy, hydroxy, or carboxy. 4A can be selected from the group consisting of hydrogen substituents, alkyl, alkoxy, alkoxyalkyl, hydroxy, hydroxyalkyl, carboxy, carboxyalkyl, alkanoyl, and alkanoylalkyl, where the alkyl and alkyl portions of the alkoxy, alkoxyalkyl, hydroxyalkyl, carboxyalkyl, alkanoyl, and alkanoylalkyl have 1 to 5 carbon atoms, which may be optionally substituted with one or more substituents selected from the group consisting of OH, CH3, and =O. Preferably, R 4A is a hydrogen substituent, methyl, methoxy, hydroxy, or carboxy.

[0030]

[29] For certain substrates with six carbon atoms, R 1 and R 3A can both be hydroxy, and R 4Acan be carboxylated, resulting in a substrate of general formula IV being glucaric acid (or generally 2,3,4,5-tetrahydroxyhexanedioic acid) and a dicarbonyl intermediate of general formula VA being 2-keto-3-deoxyglucaric acid (2,3-dihydroxy-5-oxohexanedioic acid). In this case, the degradation product of general formula IIB can be pyruvate, which can be hydrogenated as described above to produce lactic acid as the final product of general formula IIIB. The second degradation product of general formula IIC can be 2-hydroxy-3-oxopropanoic acid, which can be hydrogenated as described above to produce glyceric acid. For certain other substrates with six carbon atoms, R 1 and R 3A can both be hydroxy, and R 4A can be methanoylated, resulting in the substrate of general formula IV being 2,3,4,5-tetrahydroxy-6-oxohexanoic acid and the dicarbonyl intermediate of general formula VA being 4,5-dihydroxy-2,6-dioxohexanoic acid. In this case, the degradation product of general formula IIB can be pyruvate, which can be hydrogenated as described above to produce lactic acid as the final product of general formula IIIB. The second degradation product of general formula IIC can be 2-hydroxymalonaldehyde, which can be hydrogenated to produce glyceraldehyde.

[0031]

[30] According to even more specific embodiments, R of the compound of FIG. 2A The parts are: [ka] which can be represented by the formula R 4A contains a methylene (-CH2-) carbon atom, in which case R 4A can be selected from the group consisting of alkyl, alkoxyalkyl, hydroxyalkyl, carboxyalkyl, and alkanoylalkyl. According to such embodiments, the starting compound of general formula IV and the dicarbonyl intermediate compound of general formula VA are respectively represented by general formulas VI and VIIA: [ka] R 1 and R 3A The moiety may be as defined above, and R 5A The moiety can be selected from the group consisting of hydrogen substituents, alkyl, alkoxy, alkoxyalkyl, hydroxy, hydroxyalkyl, carboxy, carboxyalkyl, alkanoyl, and alkanoylalkyl, where the alkyl and alkyl portions of the alkoxy, alkoxyalkyl, hydroxyalkyl, carboxyalkyl, alkanoyl, and alkanoylalkyl have 1 to 4 carbon atoms, optionally substituted with one or more substituents selected from the group consisting of OH, CH, and =O. Preferably, R 5A is a hydrogen substituent, methyl, methoxy, hydroxy, or carboxy.

[0032]

[31] In another embodiment of the specific substrate having six carbon atoms, R 1 , R 3A , and R 5A can be hydroxy, such that the substrate of general formula VI is gluconic acid (or generally 2,3,4,5,6-pentahydroxyhexanoic acid) and the dicarbonyl intermediate of general formula VIIA is 2-keto-3-deoxygluconic acid (4,5,6-trihydroxy-2-oxohexanoic acid). In this case, the degradation product of general formula IIB can be pyruvate, which can be hydrogenated as described above to produce lactic acid as the final product of general formula IIIB. The second degradation product of general formula IIC can be glyceraldehyde, which can be hydrogenated as described above to produce glycerol.

[0033]

[32] Typical reaction environments relevant to the synthesis of the decomposition products and / or final products by the methods described herein include high hydrogen partial pressures, e.g., at least 3 megapascals (MPa) (435 psi), optionally in combination with a hydrogenation catalyst. In this hydrogenation / reduction environment, the terminal aldehyde group of the second decomposition product of general formula IIC can be converted to a terminal alcohol, i.e., a hydroxy (—OH), group. The decomposition product and second decomposition product can also be converted to other possible conversion products, as described in more detail below with respect to a more specific embodiment shown in FIG. 2.

[0034]

[33] In Figure 2, gluconic acid was used as the starting compound, i.e., the compound of formula I, and R 2A but: [ka] The synthesis method illustrated in Figure 1, which represents a portion of the general formula of this compound shown in Figure 1, is exemplified. In this embodiment, the dicarbonyl intermediate of formula IIA is 2-keto-3-deoxygluconic acid (2-keto-4,5,6-trihydroxyhexanoic acid), as shown in the figure. This dicarbonyl intermediate can then be decomposed to produce a degradation product of formula IIB, which in the embodiment illustrated in Figure 2 is pyruvic acid. In addition, a second degradation product of formula IIC is also produced, which in this embodiment is glyceraldehyde, and accordingly, the R 2C teeth: [ka] This is the part of R shown above. 2A It corresponds to the part, but has one less carbon atom.

[0035]

[34] As shown in Figure 2, final products and further conversion products can also be produced using the reaction conditions described herein. For example, lactic acid can be produced by hydrogenating / reducing pyruvic acid, the degradation product of Formula IIB. As shown here, glycerol can be produced by hydrogenating / reducing glyceraldehyde, the second degradation product of Formula IIC. Furthermore, as shown in Figure 2, the resulting glyceraldehyde can be converted to lactic acid by further reactions, such as those involving 1,2-hydrogen transfer or hydrogen rearrangement (Cannizzaro reaction). Thus, although a first portion of this lactic acid can be obtained by hydrogenating pyruvic acid, which is produced in equimolar amounts with glyceraldehyde by the degradation reaction, according to certain embodiments, lactic acid can be produced in molar amounts that exceed the molar amount of glyceraldehyde produced. That is, glyceraldehyde can be converted to a second portion of lactic acid, such that the reaction mixture can include the combined first and second portions of lactic acid, which lactic acid exceeds the amount of glyceraldehyde on a molar basis. For example, the ratio of the total molar amount of lactic acid to the molar amount of net glyceraldehyde (e.g., in the reaction mixture after completion of the synthesis process) can be at least 1.2, at least 1.5, or at least 2.0. At least a portion of this excess can be attributed to the conversion of glyceraldehyde to lactic acid. Additionally, as shown in Figure 2, lactic acid can be further reacted under the reaction conditions described herein to produce propylene glycol and acrylic acid as additional conversion products.

[0036]

[35] Accordingly, a representative method for synthesizing an α-hydroxycarboxylate end product having fewer carbon atoms than the α-,β-dihydroxycarboxylate starting compound is described herein. The method includes reacting the α-,β-dihydroxycarboxylate starting compound in a reaction mixture preferably containing a cracking catalyst, i.e., a catalyst or promoter for the reaction step shown as "Cracking" in Figures 1 and 2. Preferred cracking catalysts include one or more cracking active metals, such as tungsten, molybdenum, and / or vanadium, which may be present in the reaction mixture in the form of their corresponding salts, e.g., tungstate, molybdate, or vanadate (including metatungstate, paratungstate, metamolybdate, paramolybdate, metavanadate, or paravanadate). Representative tungstates are salts of Group 1 (alkali) metals or Group 2 (alkaline earth) metals, and ammonium salts. Representative examples include ammonium metatungstate and ammonium paratungstate. The decomposition catalyst (e.g., ammonium metatungstate) can be present in the reaction mixture in an amount of 0.1 mol% to 30 mol%, 0.5 mol% to 10 mol%, or 1 mol% to 5 mol% based on the moles of the substrate, for example, based on the composition of the initial reactor charge in a batch reaction or the steady-state composition in a continuous reaction. Additionally or alternatively, the decomposition catalyst can be present in the reaction mixture in an amount such that the moles of a metal (e.g., tungsten, molybdenum, or vanadium) having decomposition activity account for 6 mol% to 50 mol%, or 10 mol% to 35 mol% of the moles of the substrate. Other decomposition catalysts include solid acids and / or Lewis acids (e.g., organometallic compounds such as organotin compounds).

[0037]

[36] According to these methods, an α-hydroxycarboxylate end product, such as lactic acid, is produced by combining decomposition and hydrogenation. A further aspect of the present invention relates to the discovery that the use of a base, such as a hydroxide, can facilitate the conversion of at least a portion of the aldehyde product, such as glyceraldehyde, obtained by decomposition to an additional amount of the end product. For example, glyceraldehyde can be further reacted, such as by a reaction involving 1,2-hydrogen transfer or hydrogen rearrangement (Cannizzaro reaction), thereby converting or isomerizing it to an additional amount of lactic acid. This additional amount of end product can be expressed relative to a baseline amount in the absence of a base, or, if present, in a nominal amount. This additional amount of end product can be expressed as an increase of at least 10 mol%, at least 20 mol%, or at least 50 mol% relative to the baseline amount. Accordingly, the reaction mixture can include a base, such as a hydroxide, to facilitate the production of such additional amounts of the end product. Representative hydroxides include ammonium hydroxide as well as alkali and alkaline earth metal hydroxides such as lithium hydroxide, sodium hydroxide, potassium hydroxide, etc., with lithium hydroxide being preferred.

[0038]

[37] Certain methods relate to the synthesis of lactic acid from α-,β-dihydroxycarboxylate starting compounds having more than three carbon atoms, such as salts of gluconic acid (or generally 2,3,4,5,6-pentahydroxyhexanoate); 2,3,4,5-tetrahydroxy-6-oxohexanoate; glucaric acid (or generally 2,3,4,5-tetrahydroxyhexanedioate); 2,3,4,5-tetrahydroxypentanoate; 2,3,4-trihydroxy-5-oxopentanoate; 2,3,4-trihydroxypentanedioate; erythronate (or generally 2,3,4-trihydroxybutanoate); 2,3-dihydroxy-4-oxobutanoate; or tartrate. As described herein, an exemplary method includes dehydrating the starting compound to convert the alpha hydroxy group to a second carbonyl group and removing the beta hydroxy group to produce a dicarbonyl intermediate, and decomposing the dicarbonyl intermediate by cleaving between the beta and gamma carbon atoms of the dicarbonyl intermediate (corresponding to the beta and gamma carbon atoms to the carboxylate group of the starting compound) to produce pyruvate. The method further includes hydrogenating or reducing the pyruvate to produce lactic acid, and optionally further conversion products such as propylene glycol or acrylic acid.

[0039]

[38] According to certain embodiments, the overall yield of the decomposition product, secondary decomposition product, or any particular final product and / or further conversion product described herein, based on the theoretical yield when proceeding along each of the pathways also described herein, can generally be at least 25 mol% (e.g., 25 mol% to 90 mol%), typically at least 35 mol% (e.g., 35 mol% to 80 mol%), and often at least 50 mol% (e.g., 50 mol% to 75 mol%). These yields may apply, for example, to (i) any degradation product of general formula IIB, such as pyruvic acid, or any other specific degradation product having this general formula described herein; (ii) any second degradation product of general formula IIC, such as glycerol, or any other specific degradation product having this general formula described herein; (iii) any end product of general formula IIIB, such as lactic acid, or any other specific end product having this general formula described herein; (iv) any end product obtained by converting (e.g., hydrogenating) the second degradation product of general formula IIC, such as glycerol, or any other specific conversion product of this type described herein; and / or (v) any further conversion product described herein, such as propylene glycol or acrylic acid.

[0040]

[39] The reaction mixture, preferably an aqueous reaction mixture, can further comprise a hydrogenation catalyst, such as a solid (heterogeneous) catalyst. Exemplary hydrogenation catalysts can include one or more hydrogenation-active metals selected from Groups 8-11 of the Periodic Table, such as ruthenium (Ru), cobalt (Co), nickel (Ni), platinum (Pt), palladium (Pd), or gold (Au). A preferred hydrogenation-active metal is ruthenium. The catalyst can further comprise a solid support of the hydrogenation-active metal, with the metal dispersed on the solid support, for example, preferentially near the outer surface of the solid support or substantially uniformly throughout the porous solid support, depending on the specific catalyst preparation technique used (e.g., evaporative impregnation of a solution of the hydrogenation-active metal). Preferably, the hydrogenation-active metal or combination of such metals is present in an amount of 1 wt % to 15 wt %, or 2 wt % to 10 wt %, based on the total weight of the hydrogenation catalyst.

[0041]

[40] The hydrogenation-active metal can be present in the reaction mixture in an amount representing 1 mol% to 20 mol% or 2 mol% to 10 mol% of moles of hydrogenation-active metal (e.g., ruthenium) relative to the number of moles of substrate, for example, according to the composition of the initial reactor charge in the case of a batch reaction, or according to the steady-state composition in the case of a continuous reaction. The solid support is preferably refractory in the reaction mixture and under the synthesis reaction conditions described herein. Exemplary solid supports include one or more metal oxides, such as aluminum oxide (alumina), silicon oxide (silica), titanium oxide (titania), zirconium oxide (zirconia), magnesium oxide (magnesia), strontium oxide (strontia), etc. A preferred solid support is carbon. According to certain embodiments, the hydrogenation catalyst comprises ruthenium on a carbon support, and the ruthenium is present in the amount in the ranges given above based on the total weight of the catalyst and / or in the amount in the ranges given above based on the number of moles of substrate.

[0042]

[41] The reaction conditions maintained in the reaction mixture during synthesis of the cracking products and / or final products include elevated pressures and hydrogen partial pressures. Typical absolute pressures in the reactor generally range from 2.07 MPa (300 psi) to 24.1 MPa (3500 psi), typically from 3.45 MPa (500 psi) to 20.7 MPa (3000 psi), and often from 10.3 MPa (1500 psi) to 17.2 MPa (2500 psi). The reactor pressure can be generated primarily or substantially by hydrogen, so that these total pressure ranges can also correspond to ranges of hydrogen partial pressures. However, due to the presence of gaseous species such as ammonia and / or water vapor volatilized from the reaction mixture, the hydrogen partial pressure may be lower than these total pressures. In such cases, for example, the hydrogen partial pressure may generally be in the range of 1.38 MPa (200 psi) to 22.4 MPa (3250 psi), typically in the range of 2.41 MPa (350 psi) to 19.0 MPa (2750 psi), and often 8.62 MPa (1250 psi) to 15.5 MPa (2250 psi).

[0043]

[42] Other reaction conditions include temperatures of 100°C to 350°C, preferably 130°C to 230°C. The reaction time, i.e., the time during which the reaction mixture is maintained under any target pressure and temperature conditions, or any target subrange within the pressure and temperature ranges given above (e.g., a target total pressure of 13.8 MPa (2000 psi) and a target temperature of 160°C), is 0.5 hours to 24 hours, preferably 1 hour to 5 hours, in the case of a batch reaction. In the case of a continuous reaction, these reaction times correspond to the residence time of the reactor. Continuous operation can be carried out, for example, by continuously feeding the substrate and hydrogen under the above-mentioned pressure and temperature conditions and continuously withdrawing the reaction mixture containing the cracked products and / or end products. Continuous operation can further include continuous purification of the cracked products and / or end products, continuous separation of a process stream containing unconverted gaseous and / or liquid products, and / or continuous recycling of one or more such process streams back into the reaction mixture maintained in the synthesis reactor. In the case of recycle operation, the yield of the decomposition products and / or final products corresponds to the "once-through" or "per-pass" yield as described above, and recycling can improve the overall yield. [Example]

[0044]

[43] Example 1

[44] Sodium gluconate (10 grams) was mixed with 100 mL of water, 2.5 mol% of a commercially available ruthenium-on-carbon catalyst based on the sodium gluconate substrate, 2.5 grams or 2 mol% of tungstate in the form of ammonium metatungstate hydrate, and 1 equivalent of lithium hydroxide in a 450 cubic Hastelloy® C2000 Parr high-pressure reactor. The reactor was purged three times with 1000 psi (6.9 MPa) of nitrogen and then three times with 1000 psi (6.9 MPa) of hydrogen. After the third hydrogen flush, the reactor was pressurized to 500 psi (3.4 MPa) with hydrogen and heated to 180°C (392°F) while stirring at 700 rpm. Once the reaction temperature was reached, additional hydrogen was added to the reactor to bring the hydrogen pressure to 1300 psi (9.0 MPa). After 2 hours, the reactor contents were cooled to room temperature by suppressing with an ice-water bath, the reactor was depressurized, and the contents were filtered to recover the catalyst. The sample was then silylated with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) and trimethylchlorosilane (TMCS) in pyridine for GC / MS analysis. Analysis showed a conversion of greater than 99% of the substrate, giving 14.1 weight percent lactic acid (38.4 mole percent yield), 1.6 weight percent glycerol (4.3 mole percent yield), 3.4 weight percent ethylene glycol (13.5 mole percent yield), and 5.2 weight percent propylene glycol (16.8 mole percent yield).

[0045]

[45] Example 2

[46] The equipment and procedure of Example 1 were followed, except that hydrogen was used at 13.8 MPa (2000 psi) and no lithium hydroxide was added. Over 98 percent of the substrate was converted to a product containing 0.6 weight percent lactic acid (1.6 mole percent yield), 3.3 weight percent glycerol (8.8 mole percent yield), 1.2 weight percent ethylene glycol (4.8 mole percent yield), and 1.0 weight percent propylene glycol (3.2 mole percent yield).

[0046]

[47] Example 3

[48] ​​The conditions of Example 2 were repeated except that tungstate was not used and nitrogen was used instead of hydrogen to pressurize the reactor. The molar conversion of the substrate decreased to 92.7 percent. The products included 4.97 weight percent lactic acid (13.1 mole percent yield), 5.3 weight percent glycerol (13.7 mole percent yield), 1.5 weight percent ethylene glycol (5.7 mole percent yield), and 2.1 weight percent propylene glycol (6.5 mole percent yield).

[0047]

[49] Example 4 For this example, neither tungstate nor a commercial ruthenium-on-carbon catalyst was used, and again nitrogen was substituted for hydrogen, except at a pressure of 1.0 MPa (150 psi). The substrate was completely converted, and the products included 1.29 weight percent lactic acid (3.4 mole percent yield), 4.8 weight percent pyruvic acid (13.11 mole percent yield), and 0.3 weight percent 5-hydroxymethyl-2-furancarboxylic acid (HMFCA) (4.7 mole percent yield), with no observable glycerol, ethylene glycol, or propylene glycol.

[0048]

[51] Example 5

[52] In this example, 10 grams of calcium erythronate was used as the substrate, again using 13.8 MPa (2000 psi) hydrogen, 2.5 mole percent of a commercial ruthenium-on-carbon catalyst relative to the substrate, and 2 mole percent tungstate. After 2 hours at 180 degrees Celsius, all of the substrate was converted, and the products included 0.9 weight percent lactic acid (1.7 mole percent yield), 11.7 weight percent glycerol (22.2 mole percent yield), 0.7 weight percent ethylene glycol (2.0 mole percent yield), and 1.8 weight percent propylene glycol (4.1 mole percent yield).

[0049]

[53] Broadly, aspects of the present invention relate to the use of the synthesis methods described herein to produce degradation products and / or end products from readily available or easily derived substrates. The end products and optional further conversion products described herein can be produced by further converting the degradation products (including the second degradation products described herein) either in situ or in a further, separate reaction step. The degradation products and / or end products have fewer carbon atoms than the substrates used to produce them. This method advantageously addresses various shortcomings of conventional methods. Those skilled in the art will recognize that, using knowledge gained from this disclosure, various modifications can be made to these processes to achieve these and other advantages without departing from the scope of the present disclosure. Accordingly, it should be understood that features of the present disclosure are susceptible to modification and / or substitution without departing from the scope of the present disclosure. The specific embodiments illustrated and described herein are for illustrative purposes only and are not intended to limit the invention as defined by the appended claims.

Claims

[Claim 1] 1. A method for synthesizing an end product α-hydroxycarboxylic acid or ester thereof having fewer carbon atoms than a starting compound which is an α-,β-dihydroxycarboxylic acid or ester thereof, comprising: reacting the α-,β-dihydroxycarboxylic acid or ester thereof starting compound in a reaction mixture under hydrogen pressure and containing a cracking catalyst to produce the α-hydroxycarboxylic acid or ester thereof final product; the decomposition catalyst comprises at least one selected from the group consisting of tungstate, molybdate, and vanadate; The α-,β-dihydroxycarboxylic acid or ester thereof starting compound has the general formula I or the general formula IV, The method wherein the α-hydroxycarboxylic acid or ester thereof final product has Formula IIIB: 【Chemistry 1】 wherein R 1 is selected from the group consisting of alkoxy, alkoxyalkyl, hydroxy, and hydroxyalkyl, the alkyl portion of the alkoxy, alkoxyalkyl, and hydroxyalkyl having 1 to 5 carbon atoms optionally substituted with one or more substituents selected from the group consisting of —OH, —CH 3 , and ═O; R 2A is selected from the group consisting of alkyl, alkoxy, alkoxyalkyl, hydroxy, hydroxyalkyl, carboxy, carboxyalkyl, alkanoyl, and alkanoylalkyl, wherein the alkyl and alkyl portions of the alkoxy, alkoxyalkyl, hydroxyalkyl, carboxyalkyl, alkanoyl, and alkanoylalkyl have 1 to 5 carbon atoms which may be optionally substituted with one or more substituents selected from the group consisting of —OH, —CH 3 , and ═O. 【Chemistry 2】 wherein R 1 is selected from the group consisting of alkoxy, alkoxyalkyl, hydroxy, and hydroxyalkyl, the alkyl portion of the alkoxy, alkoxyalkyl, and hydroxyalkyl having 1 to 5 carbon atoms optionally substituted with one or more substituents selected from the group consisting of —OH, —CH 3 , and ═O; R 3A is selected from the group consisting of hydrogen, alkoxy, hydroxy, and carboxy, wherein the alkyl portion of the alkoxy has 1 to 5 carbon atoms optionally substituted with one or more substituents selected from the group consisting of -OH, -CH 3 , and =O; R 4A is selected from the group consisting of hydrogen, alkyl, alkoxy, alkoxyalkyl, hydroxy, hydroxyalkyl, carboxy, carboxyalkyl, alkanoyl, and alkanoylalkyl, wherein the alkyl and alkyl portions of the alkoxy, alkoxyalkyl, hydroxyalkyl, carboxyalkyl, alkanoyl, and alkanoylalkyl have 1 to 5 carbon atoms which may be optionally substituted with one or more substituents selected from the group consisting of —OH, —CH 3 , and ═O. 【Transformation 3】 wherein R 1 is selected from the group consisting of alkoxy, alkoxyalkyl, hydroxy, and hydroxyalkyl, and the alkyl portion of the alkoxy, alkoxyalkyl, and hydroxyalkyl has 1 to 5 carbon atoms which may be optionally substituted with one or more substituents selected from the group consisting of —OH, —CH 3 , and ═O.

Images