Stabilized non-cyclic saccharide compound as well as preparation method and application thereof

Abstract

The invention discloses a stable non-cyclic saccharide compound as well as a preparation method and application thereof. The stable non-cyclic saccharide complex comprises a layered double hydroxide (LDH) substrate and a non-cyclic saccharide embedded in an interlayer region of the LDH substrate, and the stable non-cyclic saccharide in the LDH substrate provides an opportunity to directly functionalize into other valuable molecules in the pharmaceutical, chemical or carbohydrate industry. In addition, non-cyclic saccharides are stabilized through an LDH base material, a new way of saccharide conversion and aldol condensation is achieved, and related defects of enzyme catalysts are avoided.

Description

Technical Field

[0001] This invention relates to a stabilized acyclic glycoside complex, a method for preparing the stabilized acyclic glycoside complex, and its applications. Background Technology

[0002] Currently, in the circular economy, the chemical conversion of carbohydrates into building block chemicals or high-value chemicals has been extensively studied. For example, the inventors have demonstrated that biomass-derived carbohydrates (such as fructose, glucose, cellodisaccharides, starch, and cellulose) can be directly chemically converted into 5-hydroxymethylfurfural (HMF) under mild conditions using eutectic ternary molten salt melts. Furthermore, it has been reported that acid-functionalized mesoporous carbon nanoparticles (MCN) or activated carbon can extract polysaccharides from biomass and hydrolyze them into monosaccharides and valuable chemicals. Zeolite-templated carbon materials can also be used to degrade glucan. Additionally, metal-doped carbon materials can achieve the hydrogenation of carbohydrates to produce sugar alcohols, such as sorbitol and mannitol.

[0003] Since glucose is the most abundant natural monomeric unit among carbohydrates, and fructose is the most reactive monosaccharide for producing valuable compounds such as 5-hydroxymethylfurfural (HMF) and levulinic acid, the conversion of glucose into fructose can be considered an important reaction in various industrial processes involving sugars. In studies of glucose-to-fructose conversion, acyclic sugars are considered key intermediates in sugar isomerization; however, due to the difficulty in detecting these unstable intermediates, direct evidence of their high reactivity is still lacking.

[0004] For the reasons mentioned above and others below, developing a method for stabilizing acyclic sugars has great potential for sugar conversion and its various applications. Summary of the Invention

[0005] One object of the present invention is to stabilize acyclic sugars, thereby providing the opportunity to directly functionalize such acyclic substances into other valuable molecules in the pharmaceutical, chemical or carbohydrate industries.

[0006] Another objective of this invention is to utilize a novel approach to isomerize sugars and prepare aldol condensation products via noncyclic sugars, without the associated drawbacks of enzyme catalysis.

[0007] According to the above and other objectives, the present invention provides a method for preparing the stabilized acyclic sugar, comprising: providing a collapsed layered double hydroxide substrate (collapsed LDH-based material); mixing cyclic sugars and the collapsed LDH substrate in a solvent; and reconstructing the collapsed LDH substrate into a layered structure, and embedding the acyclic sugars generated by ring-opening of the cyclic sugars into the interlayer region of the LDH substrate. The solvent used in the step of mixing the cyclic sugars and the collapsed LDH substrate may be water. Accordingly, the present invention provides a stable acyclic sugar complex comprising a layered double hydroxide (LDH) substrate and acyclic sugars embedded in the interlayer region of the LDH substrate.

[0008] Furthermore, the present invention also provides a method for sugar isomerization, comprising: embedding a non-cyclic sugar into the interlayer region of an LDH substrate; and converting the non-cyclic sugar into an isomer within the interlayer region of the LDH substrate. Accordingly, the present invention provides a novel pathway for sugar conversion (e.g., glucose-fructose conversion) using a non-cyclic sugar that can be stabilized within an LDH substrate, providing the advantages of reusability and recyclability of the LDH substrate to minimize cost and environmental impact. The step of embedding the non-cyclic sugar can be performed by equilibrating the collapsed LDH substrate and the sugar in a solvent. The solvent used for equilibration can be water, and the conversion of the non-cyclic sugar can be carried out in the presence of water within the interlayer region of the LDH substrate.

[0009] Stable acyclic glycosidic complexes can be identified by the presence of characteristic aldehyde or ketone peaks in nuclear magnetic resonance (NMR) spectroscopy. For example, in one or more embodiments of the present invention, the stabilized acyclic glycosidic complex has at least one characteristic peak in a solid-state carbon NMR spectrum within a chemical shift range of 165 to 190 ppm. Further, in solid-state hydrogen NMR spectroscopy analysis, hydrogen atoms on the aldehyde groups of the acyclic glycosidic complex can be observed at approximately 9 ppm. Furthermore, the recovery of the layered structure from the glycosidic LDH substrate can be verified by powder X-ray diffraction (PXRD) analysis. For example, in one or more embodiments of the present invention, after the collapsed LDH substrate has been equilibrated with the cyclic glycosidic complex, peaks corresponding to the (0 0 3), (0 0 6), and (0 0 9) crystal planes can be observed in the PXRD pattern.

[0010] The stable acyclic sugar complex of the present invention can undergo a variety of reactions, including but not limited to aldol condensation and acetylation. Accordingly, the present invention further provides a method for preparing an aldol condensation product, comprising: providing a stabilized acyclic sugar complex; and subjecting the acyclic sugars of the stabilized acyclic sugar complex to a condensation reaction with a carbonyl-active compound (such as a ketone compound and other carbonyl-containing compounds) to form an aldol condensation product. In one or more embodiments of the present invention, the stabilized acyclic sugar complex is stirred in acetone, which is the carbonyl-active compound, to produce the desired adduct. Furthermore, in one or more embodiments, glucose is acetylated after treatment with hydrotalcite oxide (HTO) to verify the presence of fructose.

[0011] In this invention, the reconstruction and ring-opening steps can be carried out at room temperature above 4 degrees Celsius for at least 2 hours as an equilibrium reaction. After the equilibrium reaction, acyclic sugars and isomerized sugars can be observed.

[0012] In this invention, a collapsed LDH substrate can be obtained by calcining the LDH substrate. For example, in one or more embodiments of this invention, M 3+ / N 2+ -LDH(M 3+ = Trivalent metal ions, N 2+ = divalent metal ions), such as Al 3+ / Mg 2+ -LDH can be calcined at 450°C or higher (e.g., about 550°C) to obtain a collapsed LDH substrate for stabilizing acyclic sugars, including but not limited to glucose, fructose, cellodisaccharide, galactose, maltose, fucose, 2-deoxyglucose, and mannose, or one or more of these. In another embodiment of the collapsed LDH substrate, metal-loaded HTO (e.g., ruthenium-loaded HTO, copper-loaded HTO, and the like) can be obtained by wet impregnation with HTO or by co-precipitation followed by calcination. Thus, the dominant metal ion (e.g., aluminum ion) in the LDH lattice can be partially replaced by a loaded metal ion (e.g., ruthenium or copper ion), and the content of the loaded metal ion can be greater than 0 to 10% by weight based on the total weight of the LDH substrate. In one or more embodiments, a reduction reaction can be performed to produce metal-loaded HTO (e.g., ruthenium-loaded HTO, copper-loaded HTO, and the like). Accordingly, in one or more embodiments of the present invention, by balancing the collapsed LDH substrate with sugars, open-ring glucose, fructose, mannose, cellodisaccharide, galactose, maltose, fucose, 2-deoxyglucose or mixtures thereof can be stabilized in the interlayer region of the LDH substrate.

[0013] As used in this article, the term "room temperature" refers to a temperature greater than 4 degrees Celsius, preferably greater than 4 degrees Celsius to 40 degrees Celsius, such as 15-35 degrees, 15-30 degrees, 15-24 degrees and 16-21 degrees Celsius.

[0014] As used in this article, the phrase “one or more of A, B and C” should be interpreted as meaning the logic of using the non-exclusive logic “or” (A or B or C), and should not be understood as meaning “at least one of A, at least one of B, and at least one of C”.

[0015] As used herein, the term "layered double hydroxide (LDH) substrate" refers to a material having a positively charged layer and weakly bound charge-balancing anions (located in the interlayer region) that possesses a structural memory effect, thus enabling the reconstruction of a damaged layered structure under certain circumstances, rebuilding from a collapsed LDH-based material into a rehydrated LDH-based material. The LDH substrate referred to herein is not specifically limited and can be any single-metal LDH, multi-metal LDH (e.g., binary, ternary, quaternary LDH), or its derivatives (e.g., silicon-containing LDH derivatives (such as those disclosed in U.S. Patent Application No. 16 / 454,893), ruthenium-loaded LDH derivatives, copper-loaded LDH derivatives, and LDH derivatives loaded with any other metal). LDH can be represented by the following general formula: M x 3+ N (1-X) 2+ (OH)2A n- yH2O, where M 3+ and N 2+ They are trivalent and divalent metal ions, respectively, A n- These are interlayer ions with an n-valent oxidation state. The x-value represents the proportion of trivalent metal ions in the total number of metal ions, and y represents the change in interlayer water. Common forms of LDH contain Mg. 2+ With Al 3+ Al is used as the main metal species in the LDH lattice (i.e., Al). 3+ / Mg 2+ -LDH, also known as hydrotalcite) and Mg 2+ with Fe 3+ (i.e., Fe) 3+ / Mg 2+ - LDH, also known as pyroaurites. Furthermore, other metals besides the primary metal species can also bind to LDH to form metal-loaded M... 3+ / N 2+-LDH (e.g., HT loaded with copper ions, HT loaded with ruthenium ions, and HT loaded with other metal ions).

[0016] As used in this article, the term "saccharide" refers to the collective term for polyhydroxy aldehydes or polyhydroxy ketones and their condensation polymers and derivatives, whose empirical formula is close to C0. m (H2O) n , where m and n are the same or approximately the same integers. This term is not intended to be limited to any sugars, but includes monosaccharides, disaccharides, oligosaccharides, polysaccharides and their derivatives (e.g., N-acetylglucosamine, glucosamine and any other amino sugars).

[0017] Examples of monosaccharides or their derivatives include glucose, fructose, mannose, 2-deoxyglucose, galactose, fucose, rhamnose, xylose, sorbose, talose, allose, gulose, idose, arabinose, lyxose, ribose, gluconic acid, glucuronic acid, and galacturonic acid.

[0018] Examples of disaccharides or oligosaccharides or their derivatives include maltose, cellobiose, gentiobiose, lactose, isomaltose, palatinose, melibiose, saccharose, leucrose, laminaribiose, sophorose, cellotriose, xylobiose, mannobiose, panose, maltotriose, isomalttriose, maltotetraose, maltopentaose, maltohexaose, maltoheptaose, α-cyclodextrin, β-cyclodextrin, etc.

[0019] Examples of polysaccharides and their derivatives include starch, cellulose, chitin, glycogen, xylan, arabinoxylan, mannan, galactomannan, callose, fucoidan, laminarin, chrysolaminarin, amylopectin, dextrins, maltodextrins, inulin, dextran, and polydextrose.

[0020] These and other features and advantages of the present invention will be further described and more readily understood from the following detailed description of preferred embodiments. Attached Figure Description

[0021] Figure 1 High-resolution electrospray ionization mass spectra (ESI-MS) of the adducts of aldol condensation reaction are shown;

[0022] Figure 2 The tandem mass spectrum (MS / MS) of the adducts of the aldol condensation reaction is shown.

[0023] Figure 3 A schematic diagram showing the heating procedure of a gas chromatography column;

[0024] Figure 4 Showing (a) pure 13 C6-labeled glucose ( 13 (c6-Glc), (b) and physically mixed with hydrotalcite oxide (HTO) 13 C6-Glc, (c) adsorbed in mesoporous carbon nanoparticles (MCN) 13 C6-Glc and (d) adsorbed in rehydrated hydrotalcite (HTR) 13 Solid-state carbon NMR spectrum of C6-Glc ( 13 C CP / MAS NMR), where all reaction times and initial solution concentrations were 2 hours and 15 mg / mL, respectively;

[0025] Figure 5 The HTR values ​​after 2, 12, and 24 hours of reaction showed 1- 13 C-labeled glucose (1- 13 Solid-state carbon NMR spectrum of C Glc;

[0026] Figure 6 The HTR values ​​after 2, 12, and 24 hours of reaction were displayed. 13 Solid-state carbon NMR spectrum of C6-Glc;

[0027] Figure 7 The HTR values ​​after 2, 12, and 24 hours of reaction were shown to contain 2- 13 C-labeled glucose (2- 13 Solid-state carbon NMR spectrum of C Glc;

[0028] Figure 8 The reaction shows (a)1- 13 C-labeled fructose (1- 13 C Fru), (b)1- 13 C Glc、(c)2- 13 C-labeled fructose (2- 13 C Fru) and (d)2- 13 Comparison of C Glc solid-state carbon NMR spectra;

[0029] Figure 9 The rotor of the covered sample is shown as 1- 13 Solid-state carbon NMR spectrum of dry C Glc-HTR powder;

[0030] Figure 10 Show (a) 13 Solid-state carbon NMR spectra of C6-Glc, (b) maltose, (c) cellodisaccharide, and (d) sorbitol after HTO reaction and changes in sugar alcohol and sugar configuration;

[0031] Figure 11 Displaying HTR interlayer 1- 13 C-labeled cellodisaccharide (1- 13 Comparison of solid-state carbon NMR spectra of C Cel with those of general cellodisaccharides;

[0032] Figure 12 Comparison of solid-state carbon NMR spectra of acyclic glucose in HTO, ruthenium-loaded HTO, and copper-loaded HTO, respectively.

[0033] Figure 13 This shows that acyclic glucose is embedded within the HTR interlayer;

[0034] Figure 14 The solid-state 1H NMR spectra of fructose, glucose, and cellodisaccharide after the reaction are shown. 1 H MAS NMR), with a rotation frequency of 30kHz;

[0035] Figure 15The solid-state 1H NMR spectra of mannose, galactose, 2-deoxyglucose, and sorbitol after the reaction are shown. 1 H MAS NMR), with a rotation frequency of 10kHz;

[0036] Figure 16 This demonstrates the noncyclic sugar stabilization mechanism of HT;

[0037] Figure 17 Displaying the powder X-ray diffraction spectra of HT, HTO, and HTR;

[0038] Figure 18 The powder X-ray diffraction spectra of the processed 2-deoxyglucose, maltose, glucose, galactose, fucose and cellodisaccharide are shown.

[0039] Figure 19 Powder X-ray diffraction spectra of ruthenium-loaded hydrotalcite oxide (Ru@HTO) and glucose-adsorbed ruthenium-atom hydrotalcite oxide (r-Ru@HTO); and

[0040] Figure 20 Powder X-ray diffraction spectra of copper-loaded hydrotalcite oxide (Cu@HTO) and glucose-adsorbed copper-atom hydrotalcite oxide (r-Cu@HTO). Detailed Implementation

[0041] chemicals

[0042] D-glucose- 13 C6、D-[2- 13 C]-glucose ( 13 C6-Glc and 2- 13 C Glc, 13 (C atom percentage 99%, Sigma-Aldrich, USA), D-[1- 13 C]-glucose(1- 13 C Glc, 13 The percentage of carbon atoms is 98-99%, Cambridge Isotope Laboratories, USA), D-[1- 13 C]-fructose, D-[2- 13 C]-fructose(1- 13 CFru and 2- 13 C Fru, 13 The percentage of C atoms is 99% (Omicron Biochemicals), D-[1- 13 C]-cellulose disaccharide (1- 13 C Cel 13C atom percentage 99%, Omicron Biochemicals, D-glucose (Glcp, ≥99.5%, Sigma-Aldrich, USA), D-fructose (Frup, ≥99%, Sigma-Aldrich, USA), D-mannose (>99%, AK Scientific, USA), D-cellulose disaccharide (Celp, ≥98%, Sigma-Aldrich, USA), D-maltose monohydrate (>99%, Sigma-Aldrich, USA), D-fucose (>98%, Sigma-Aldrich, USA), sorbitol (99%, Sigma-Aldrich, USA), 2-deoxyglucose (>97%, TCI, Japan), magnesium nitrate hexahydrate (Mg(NO3)2·6H2O, ≥98%, Alfa Aesar, UK), aluminum nitrate nonahydrate (Al(NO3)3·9H2O, ≥99%, Fluka, UK), sodium hydroxide (NaOH, ≥98%). The following are commercially available: sodium carbonate (Na₂CO₃, ≥99.8%, Sigma-Aldrich, USA), methanol (MeOH, ≥99.9%, Macron, USA), acetic anhydride (Ac₂O, 98%, Merck, Germany), pyridine (≥99%, JTBaker, USA), ethyl acetate (≥99.5%, Macron, USA), toluene (≥99.8%, Fluka, UK), and acetone (ACS grade, Macron, USA). No further purification is required before use. Deionized water is used for all applications.

[0043] method

[0044] Preparation of collapsed LDH substrate

[0045] Mg(NO3)2·6H2O (20.00 mmol) and Al(NO3)3·9H2O (6.60 mmol) were dissolved in MeOH / H2O (1:1, v / v, 200 mL) to prepare Mg 2+ With Al 3+ A mixture of methanol solutions, in which Mg 2+ With Al 3+ The molar ratio was 3:1. To promote the condensation of metal hydroxides to synthesize hydrotalcite, an alkaline solution containing NaOH (44.25 mmol) and Na2CO3 (15.79 mmol) was also prepared in MeOH / H2O (1:1, v / v, 200 mL). Next, Mg... 2+ / Al 3+The nitrate mixture was added dropwise to a methanol solution (MeOH / H2O, volume ratio 1:1, 200 mL) at a rate of 2 mL / min, and the pH was adjusted to 10 by adding the aforementioned alkaline solution. After addition, the slurry was aged for 24 hours in a closed system at 65°C in a conventional oven, and then filtered after cooling to room temperature to collect the resulting material. The lumps were dried in a muffle furnace at 90°C for 16 hours and then ground. The powder obtained by drying at 110°C for 6 hours (i.e., hydrotalcite (HT)) was then calcined in a muffle furnace at 110°C for 6 hours at a heating rate of 2°C / min, followed by calcination at 550°C for 12 hours to form hydrotalcite oxide (HTO), which is an example of a collapsed LDH substrate.

[0046] Another material obtained is metal ion-doped hydrotalcite, which is prepared by co-precipitation, in which some aluminum ions are replaced by 1, 2, 5, or 10% by weight of ruthenium or copper ions to form metal ion-hydrotalcite (M-HT; M = copper or ruthenium). Its synthesis method is the same as above, namely, through co-precipitation, gelation and filtration, followed by drying and calcination (M-HTO).

[0047] In addition, metal-ion-loaded hydrotalcite oxides (M@HTO; M = copper or ruthenium) can be synthesized via wet impregnation as another example of preparing collapsed LDH substrates, wherein the hydrotalcite oxide support contains 2% by weight of metal ions. Briefly, RuCl3·nH2O (26.1 mg; 39% ruthenium) was dissolved in deionized water (20 mL), and then added to a 50 mL round-bottom flask containing hydrotalcite oxide (HTO; 500 mg). The mixture was ultrasonically agitated to ensure thorough dispersion, followed by vigorous stirring at 60°C for 3 hours under nitrogen atmosphere. Subsequently, the solvent was removed by evaporation and lyophilized to obtain a dark gray powder product (denoted as Ru@HTO). The ruthenium ions on the HTO were then reduced at 450°C for 4 hours under hydrogen atmosphere to produce ruthenium-atom hydrotalcite oxides (denoted as r-Ru@HTO). Copper-loaded hydrotalcite oxide (represented as Cu@HTO) was prepared as above using Cu(NO3)2·3H2O (38.78 mg), and a reduction reaction was carried out to produce copper-atom hydrotalcite oxide (represented as r-Cu@HTO).

[0048] Layered structure recovery of collapsed LDH substrate

[0049] 40 mg of calcined HTO was placed in a capped 1.5 mL microcentrifuge tube containing 0.6 mL of deionized water per gram of sample and subjected to rehydration for 2 hours, followed by lyophilization for at least 12 hours. The resulting powder was the final rehydrated hydrotalcite (HTR).

[0050] Acyclic sugars stabilized within LDH substrates

[0051] Derivatized sugars, including glucose (Glcp, 13 C6-Glc, 1- 13 C Glc and 2- 13 C Glc), fructose (Frup, 1- 13 CFru and 2- 13 C Fru) and fiber disaccharides (Celp and 1- 13 CCCC was prepared in an aqueous solution (0.6 mL, concentration 15.0 mg / mL) and mixed with collapsed LDH substrate (HTO, 40 mg) in a capped 1.5 mL microcentrifuge tube. After equilibration at room temperature for 2, 12, and 24 hours, the sample was centrifuged at 3000 rpm for 3 minutes to separate the HT-derived material and the sugar solution. The supernatant was then filtered and diluted to determine the final concentration by high-performance liquid chromatography (HPLC). The HT-derived material was lyophilized overnight for analysis of its solid-state NMR spectrum (including C and H spectra). NMR spectroscopy confirmed that acyclic sugars were stabilized within the interlayer of the LDH substrate and that glucose was converted into fructose (as shown in Procedure I below).

[0052]

[0053] Process I - Glucose is converted into fructose

[0054] In addition, standard solutions of D-glucose, cellodisaccharide, galactose, maltose, L-fucose, and 2-deoxyglucose were prepared in aqueous solution at concentrations ranging from 30 mg / mL to 0.1 mg / mL, and the Langmuir adsorption isotherm after equilibration was studied using a static method. Collapsed-state LDH substrate (HTO, 40 mg) was placed in a 2 mL microcentrifuge tube containing 0.6 mL of the sugar solution. The tube was capped and equilibrated at room temperature by vortex mixing for 2 hours. The sample was then centrifuged at 3000 rpm for 3 minutes to separate the HT-derived material from the sugar solution. The supernatant was then filtered and diluted to determine the final concentration by high-performance liquid chromatography (HPLC). The sugar concentration on HTO was calculated from the measured decrease in HPLC sugar concentration using material balance. PXRD analysis confirmed that the HT-derived material exhibited a layered structure recovery.

[0055] In addition, metal-loaded hydrotalcite oxides also stabilize acyclic sugars, and these sugars were analyzed by solid-state NMR spectroscopy and powder X-ray diffraction spectroscopy.

[0056] Glycoacetylation

[0057] The dried glucose-HTO (approximately 45 mg) was suspended in an acetic anhydride O / pyridine solution (1:1, 0.5 mL, v / v) and stirred overnight at room temperature. The mixture was centrifuged at 5000 rpm for 5 minutes to separate the HTO-derived solid and the supernatant. The HTO-derived solid was washed with 1.0 mL of ethyl acetate and centrifuged to remove it; this step was repeated three times. A small amount of toluene was then added to the acetylated sugar solution, followed by concentration under reduced pressure; this step was repeated three times. The solution was then dried using a high-vacuum pump for at least 12 hours for nuclear magnetic resonance spectroscopy analysis.

[0058] Intermolecular aldol condensation

[0059] To utilize acyclic sugars, an intermolecular aldol condensation reaction was carried out by mixing sugar-derived solids with acetone (see process II below).

[0060]

[0061] Process II - Preservation of Active Acyclic Sugars via Aldol Condensation

[0062] The dried glucose-HTO (approximately 80 mg) was resuspended in acetone (1.2 mL) and stirred overnight at 50°C. The mixture was centrifuged at 5000 revolutions per minute for 5 minutes to separate the HTO-derived solid and the supernatant. The HTO-derived solid was washed with 1.0 mL of acetone and centrifuged to remove it; this step was repeated twice. The solid was then dried under high vacuum for at least 12 hours. The dried solid was resuspended in deionized water (1.0 mL) and vortexed for 10 minutes before centrifugation and filtration. The filtrate was lyophilized for at least 12 hours and then analyzed by high-resolution electrospray ionization mass spectrometry (HPLC-MS / MS). Figure 1 ) and tandem mass spectrometry ( Figure 2 Identification of adducts.

[0063] instrument

[0064] (1) High-performance liquid chromatography (HPLC) analysis

[0065] Analysis was performed using a Shimadzu Prominence LC-20AD liquid chromatography system equipped with a RID-20A refractive index detector and a UV detector with a wavelength set to 370 nm. Sugars were quantified using these two detectors. Impurities were removed using syringe filters prior to liquid chromatography analysis. The sample was extracted with a 0.01 equivalent sulfuric acid aqueous solution at 50°C (flow rate 0.6 mL / min) and passed through an ion exchange column (HPX-87H, 7.8 x 300 mm, Aminex).

[0066] (2) Nuclear magnetic resonance spectroscopy (NMR) analysis

[0067] The dried HT-derived material was made into a fine powder and loaded into 4 mm and 2.5 mm zirconia rotors for solid-state nuclear magnetic resonance spectroscopy analysis. 1 H- 13 C-interpolarized magic angle rotating nuclear magnetic resonance spectrum ( 1 H- 13C-NMR (CP / MAS NMR) was obtained using a Bruker AV 300MHz instrument equipped with a 4mm dual-resonance probe, operated at 300.13 and 75.47MHz for hydrogen-1 and carbon-13 Larmor frequencies, respectively. For the cross-polarization (CP) experiments, the contact time for hydrogen-1 and carbon-13 channels was 1 ms, and the radio-frequency (RF) intensity was 41.0 kHz. Solid-state C-NMR was obtained at a sample rotation frequency of 10 kHz and ambient temperature; chemical shifts were referenced to the carboxyl carbon signal of glycine at 176.4 ppm. Solid-state H-NMR was collected using a Bruker AVIII-800MHz instrument with a sample rotation frequency of 30 kHz; chemical shifts were referenced to tetramethylsilane (TMS) at 0 ppm. Liquid-state H-NMR analysis was performed using a Bruker AV500. Samples were prepared in heavy water (δ = 4.79 ppm). Pyridine is added to the sample at a fixed concentration as an internal calibration standard for quantification.

[0068] (3) Powder X-ray diffraction (PXRD) analysis

[0069] PXRD analysis of the sample diffraction patterns was obtained using a Bruker D8 Advance X-ray diffractometer (Brucker, USA), which operates at 40 kV and 40 mA on copper K-type surfaces. α radiation source The sample was analyzed through a 0.6 mm slit. The diffraction results were scanned within a 2θ range of 5°–90° at a scan rate of 0.5 seconds per step, with the monitor air scattering knife fixed 3 mm above the sample.

[0070] (4) Gas chromatography (GC) analysis

[0071] GC analysis was performed using a Shimadzu GC-2014 gas chromatograph equipped with a flame ionization detector (FID). The column was 30 μm long, with a film thickness of 0.25 μm and a radius of 0.32 mm. Impurities were removed using syringe filters before analysis. Chromatographic conditions: For each determination, 0.5 μL of sample was injected and heated to 200°C for vaporization. The carrier gas (helium, 99.9992%) pressure was set at 90.8 kPa, and the total flow rate was 67.5 mL / min. The purge flow rate was 3.0 mL / min, and the split ratio was 40:1. The sample flowed into the column at a rate of 1.57 mL / min. The sample was separated using a specific temperature control program. Figure 3 The outflowing gas is completely combusted at 250 degrees Celsius by a flame ionization detector.

[0072] Results section

[0073] Solid-state carbon NMR spectroscopy results

[0074] In solid-state carbon NMR spectroscopy 13 C-labeled glucose 13 An additional peak was observed in the low-field region after C6-Glc underwent the HTO reaction. Figure 4 d). The typical characteristic peaks of gluconanose are located at 90-100, 65-80, and 60-65 ppm, which represent the anomeric carbon 1 (C1), the second to fifth carbons on the ring (C2-C5), and the methylene carbon 6 (C6), respectively. Figure 4 a). 13 The carbon spectrum of a physical mixture of C6-Glc and HTO is similar to that of a pure C6-Glc. 13 C6-Glc (Figure 4b). Adsorption of mesoporous carbon nanoparticles (MCN) (through the CH-π interaction of hydrogen in sugars and aromatic functional groups) leads to peak broadening. Figure 4 c). Therefore, the disappearance of the peak at 170 ppm for glucose that is stable within the rehydrated HT (HTR) interlayer indicates a configurational change in glucose, and this peak is considered to be the aldehyde carbon of acyclic glucose.

[0075] To verify the presence of acyclic glucose, 1- was treated with HTO for different durations. 13 C-labeled glucose 1- 13 CGlc( Figure 5 ), 13 C6-Glc( Figure 6 ) and 2- 13 C-labeled glucose 2- 13 C Glc( Figure 7 Besides the two signals of 93 and 97 ppm ( Figure 5 The first carbon of α- and β-glucose also shows a broad peak of 60-80 ppm and a low-field peak of 170 ppm, indicating that 1- 13 C Glc undergoes transformation. The broad peak indicates the first carbon of fructose, which is converted via 1- 13 C-labeled fructose 1- 13 The carbon spectrum of C Fru was confirmed ( Figure 8 Most importantly, the 170 ppm peak originates from the first carbon of glucose. As processing times increased to 12 and 24 hours, the intensity of the first carbon peak of glucose weakened, while the aldehyde carbon of non-cyclic glucose and the methylene group of fructose became stronger. (Fully labeled) 13 The carbon spectra of C6-Glc also showed characteristic peak changes as the processing time increased. Figure 6The peak intensity at 170 ppm is decreasing, while the new signal at 183 ppm is becoming stronger. The broad peak at 90-110 ppm shifting to the lower field suggests carbon-2 formation of fructose (Fru, Frup, or Fruf). Repeat 2- 13 The adsorption of C Glc showed peaks of 183-ppm and 93-110-ppm due to the second carbon of the caustic soda, and the signal became stronger. Figure 7 ). 2- 13 CFru 13 The C-ray spectroscopy showed consistent signals at 65-90 ppm and 90-110 ppm, representing the second carbon of glucose (Glcp or Glc) and the second carbon of fructose (Frup and Fruf), respectively. Surprisingly, even after lyophilization, the 1- 13 The C Glc-HTR remains within the rotor used for solid-state NMR measurements, and the glucose-fructose inversion reaction continues to occur. Figure 9 Based on the changes in the three characteristic peaks, it can be seen that the residual Glcp stabilized in the rehydrated HT is still slowly catalyzed by trace amounts of water and converted into acyclic Glc, which is further converted into fructose Fru, Frup, and Fruf.

[0076] To further confirm the aldehyde carbon of the reduced terminal sugar ring-opening, sorbitol, maltose, and cellodisaccharide were subjected to the same treatment conditions and solid-state nuclear magnetic resonance carbon spectroscopy analysis. Figure 10 Clearly, when the spectrum of sorbitol only shows signals of aliphatic alcohols, maltose and cellodisaccharides stable in the HTR exhibit signals similar to those of sorbitol. 13 The same 170ppm signal as C6-Glc. Sorbitol is a sugar alcohol, specifically a hexaol, which is non-cyclic. Maltose and cellodisaccharide are composed of two glucose molecules with α- and β-1,4 linkages, respectively. LDH substrates can stabilize acyclic glucose groups through the ring-opening and ring-reopening properties of glucose moiety with reducing ends in aqueous solution. Also for 1- 13 C-cellulose disaccharide 1- 13 C Cel stabilizes the non-cyclic structure ( Figure 11 Besides the carbon signal at 90-110 ppm, which is the first carbon signal of cellodisaccharide, the two peaks at ~170 and ~70 ppm indicate the aldehyde carbon of the non-cyclic glucose group and the methylene group of the fructose group of the in-situ generated glucose (1→4). Regarding the ruthenium-loaded HTO and copper-loaded HTO, solid-state carbon NMR spectroscopy indicates that glucose has been stabilized in the metal-loaded hydrotalcite, while the characteristic peaks at 170 and 180 ppm further indicate that glucose has been preserved and stabilized in a linear morphology. Figure 12Typically, in carbon spectroscopy, aldehydes and ketones are expected to have carbon atoms in the ~200 ppm range. Because acyclic glucose and fructose are highly unstable, they achieve stability through metal hydroxides within the HT interlayer. Therefore, it is inferred that aldehydes or ketones of acyclic sugars form carbonate-like complexes with the hydroxyl groups of HT. Figure 13 This generates a corresponding carbon signal in the carbonate region.

[0077] Furthermore, aldehyde hydrogen signals for fructose, glucose, and cellodisaccharides were observed at 9 ppm in solid-state nuclear magnetic resonance (NMR) proton spectra. Figure 14 Because the conversion between glucose and fructose is reversible, the aldehyde hydrogen signal in the fructose-HTR 1H spectrum is considered to originate from acyclic glucose (as shown in Procedure I above). Other monosaccharides (such as galactose, mannose, and 2-deoxyglucose) also show aldehyde hydrogen signals in the 1H spectrum. Figure 15 The sorbitol-HTR results did not show the expected low-field peaks. The hydrogen signals in the 0-2 ppm range are characteristic peaks of HT, including Mg3OH and Mg2AlOH. Unlike high-resolution liquid NMR 1H spectra, the hydrogen and hydroxyl hydrogen signals on the primary and secondary carbons of sugars are located in the 3-7 ppm range and are difficult to distinguish. The aldehyde hydrogen signal is generally expected to be located in the lower field region of the 1H spectrum compared to the presented spectrum. As mentioned earlier, the formation of carbonate complexes to stabilize the acyclic sugars within the HTR interlayer slightly obscures the aldehyde hydrogen signal. Figure 13 ).

[0078] This invention further proposes a non-cyclic sugar stabilization mechanism for HT ( Figure 16 After the hydroxyl group on the first carbon of Glcp is deprotonated, the nearby metal hydroxide stabilizes the acyclic Glc via hydrogen bonding, especially the reactive oxocarbon anion on the fifth carbon. Simultaneously, the carbonylated first carbon of the partially positively charged acyclic Glc attracts the electron pair of the hydroxyl group, thus preserving the acyclic Glc in the HTR. Subsequently, the second hydroxyl group is deprotonated via hydroxide ions, rapidly generating a ketone. Similarly, the carbonylated second carbon and the carbon-oxygen anion on the fifth carbon remain stabilized by the metal hydroxide. Finally, the water molecule and the acyclic Fru form cyclic Frup and Fruf.

[0079] Summarize, 13 C6 glucose, after HTO treatment, exhibited an additional characteristic peak at 170 ppm. This indicates a conformational change in the conversion of glucapranose into acyclic glucose. Different treatment times were used to further refine the results. 13 C6 glucose, 1- 13 C glucose and 2- 13C-glucose is intercalated within rehydrated HT. Therefore, the characteristic peak at 170 ppm is confirmed to originate from the first carbon of glucose. After a longer reaction time, another carbonate peak appears at 183 ppm, confirmed to originate from the second carbon of fructose. Based on the observed chemical shifts, it is believed that the acyclic sugars form carbonate complexes with rehydrated HT. Related solid-state 1H NMR spectroscopy also supports this explanation. Furthermore, when the freeze-dried sample powder is placed in a rotor, a glucose-fructose conversion via acyclic glucose can be observed. This implies that the conversion can be carried out using trace amounts of water. It is believed that the acyclic sugars stabilized within rehydrated HT provide the opportunity to directly functionalize these reactive substances into other valuable molecules.

[0080] PXRD results

[0081] Figure 17 The PXRD patterns of synthesized hydrotalcite (HT), calcined hydrotalcite (HTO), and rehydrated hydrotalcite (HTR) are shown. Both HT and HTR exhibit typical patterns of well-crystallized layered structures, with peaks corresponding to the (0.03), (0.06), and (0.09) crystal planes, respectively; while the HTO sample only shows characteristic peaks of a mixed magnesium and aluminum oxide. The (0.03), (0.06), and (0.09) crystal planes represent the base layer, interlayer spacing, and brucite-like layer, respectively.

[0082] Most HT-derived materials obtained by HTO treatment of sugars have similar PXRD patterns, showing a reverting layered structure, such as... Figure 18 As shown, the layered structure of the LDH substrate can be reconstructed from sugars. The absence of a hydroxyl group at the second carbon position and the orientation of the hydroxyl group at the fourth carbon position have no significant effect on the structure reconstruction. Furthermore, the orientation of the glycosylic bond in disaccharides (cellodisaccharide and maltose) appears to have little impact on the reconstruction of the layered structure of the LDH substrate. Here, the peak intensity of the typical LDH peak in disaccharides is higher than that in monosaccharides.

[0083] Furthermore, the superior layer reconstruction exhibited by the disaccharide solution illustrates the role of hydroxyl groups in forming hydrogen bonds with the HTO surface. Because disaccharides have more hydroxyl groups, these layers are more likely to be pulled together through intercalation and / or hydrogen bonding with sugar molecules, thus enabling the reconstruction of the layered structure of the LDH substrate.

[0084] Furthermore, metal-loaded hydrotalcite also exhibits a "memory effect," meaning it can revert to its layered structure upon the introduction of appropriate anionic species. PXRD patterns show that the layered structure of Cu@HTO exhibits superior structure recovery capability. Figure 19 and 20 ).

[0085] Quantitative analysis of carbohydrate adsorption

[0086] Following HPLC analysis, the sugars adsorbed on HTO and metal-HTO were quantitatively analyzed, as shown in Tables 2 and 3. A higher percentage of adsorbed sugar indicates better adsorption capacity. Some sugars may degrade due to the mobile phase used in HPLC (0.01 equivalent sulfuric acid aqueous solution); therefore, liquid nuclear magnetic resonance (HMR) spectroscopy or gas chromatography was used for quantification.

[0087] Langmuir isothermal adsorption

[0088] The Langmuir constants of glycosyl acceptors are listed in Table 1 below.

[0089] [Table 1]

[0090]

[0091]

[0092] Of all monosaccharides, glucose exhibits the highest adsorption capacity (Q) at 87 mg per gram of HTO. m Galactose (2.673 L·mg) has a lower adsorption capacity than its stereoisomers and derivatives. Regarding the b-value, galactose (2.673 L·mg) -1 It is expected to be higher than glucose (0.546 L·mg). -1 Adsorption is relatively good. However, this does not match the corresponding adsorption results. Considering the stereoconfiguration of sugars, galactose is an epimer of glucose, possessing an axial hydroxyl group at the fourth carbon position. The low adsorption capacity may be attributed to the orientation of the axial hydroxyl group on the sugar, because out-of-plane hydroxyl groups create steric hindrance and / or other reactions, thus preventing the sugar from adsorbing from the environment to the interlayer / surface of the metal oxide. Regarding glucose dimers, the adsorption activity of cellodisaccharides with β-1,4 linkages (Q...) is... m =103.36mg g -1 It is superior to glucose and maltose with α-1,4 linkage (Q). m =75.42mg g -1 This can be explained by the orientation of the glycosidic bonds. The two D-glucopyranosyl units in the cellodisaccharide are in the same plane, but one is twisted relative to the other; while the D-glucopyranosyl units in maltose are twisted in the opposite direction. The α-1,4 linkages in maltose cause molecular bending, so the monomers are not in the same plane; therefore, maltose is more difficult to embed in the hydrotalcite layer due to its spatial arrangement. This is positively correlated with the b-value, where the cellodisaccharide value is 1.574 L mg. -1 , while maltose is 0.955 mg / L. -1 .

[0093] As for gluconoranose derivatives, deoxyglucoses (fucose and 2-deoxyglucose) also exhibit lower Q than glucose. m (80 and 69 mg respectively) -1 The possible reason for this result is the limited number of hydroxyl groups in the sugar that can interact with the functional groups on the HTO surface. It is noteworthy that the position of the hydrogen atom replacing the hydroxyl group (carbon 5 in fucose and carbon 2 in 2-deoxyglucose) is not particularly important for the adsorption behavior. Furthermore, commercially available calcined hydrotalcite (Sigma-Aldrich, USA) can also be used as an adsorbent for glucose adsorption, but results show that commercially available hydrotalcite-derived oxides adsorb almost no sugar molecules.

[0094] Sugar adsorption

[0095] The adsorption capacities of sugars are listed in Table 2 (HTO) and Table 3 (metal-HTO).

[0096] [Table 2]

[0097]

[0098]

[0099] Metal-HTO

[0100] [Table 3]

[0101]

[0102]

[0103] In the above embodiments, the adsorption of various sugars by HTO and metal-HTO (with a metal loading of greater than 0 to about 10% by weight) has been verified. Accordingly, another embodiment of the present invention provides a sugar-adsorbed complex comprising an LDH substrate and sugars adsorbed on the LDH substrate (e.g., those listed in Tables 1-3). As described above, the sugar-adsorbed complex can be obtained by equilibrating the collapsed LDH substrate and sugars in a solvent (e.g., water).

[0104] The above embodiments are for illustrating specific implementations and technical features of the present invention, and are not intended to limit the scope of protection of the present invention. Many other possible modifications and variations may be made without departing from the spirit and scope of the invention as claimed in the appended claims. The scope of the claims should be determined by the claims themselves.

Claims

1. A stabilized acyclic glycoside complex, characterized in that, include: A single-layer double hydroxide substrate (LDH substrate); and A non-cyclic sugar is embedded in the interlayer region of the LDH substrate.

2. The stabilized acyclic glycoside complex as described in claim 1, characterized in that, The LDH substrate is M 3+ / N 2+ -LDH or M supported on metal ions 3+ / N 2+ -LDH, the M 3+ It is a trivalent metal ion, and this N 2+ It is a divalent metal ion.

3. The stabilized acyclic glycoside complex as described in claim 2, characterized in that, The M 3+ For Al 3+ And the N 2+ Mg 2+ .

4. The stabilized acyclic glycoside complex as described in claim 2, characterized in that, M of the load metal 3+ / N 2+ -LDH is the M of the ruthenium load. 3+ / N 2+ -LDH or M with copper load 3+ / N 2+ -LDH.

5. The stabilized acyclic glycoside complex as described in claim 1, characterized in that, The acyclic sugar is one or more of glucose, fructose, mannose, cellodisaccharide, galactose, maltose, fucose, and 2-deoxyglucose in open-ring form.

6. The stabilized acyclic glycoside complex according to any one of claims 1-5, characterized in that, The stabilized acyclic glycoside complex exhibits at least one carbon characteristic peak in the chemical shift range of 165 to 190 ppm.

7. A method for preparing stabilized acyclic sugars, characterized in that, include: Provide a collapse-state layered double hydroxide substrate (collapse-state LDH substrate); A cyclic sugar is mixed with the collapsed LDH substrate in a solvent; as well as The collapsed LDH substrate is reconstructed into a layered structure, and the non-cyclic sugars generated by the ring-opening of the cyclic sugars are embedded in the interlayer region of the LDH substrate.

8. The method as described in claim 7, characterized in that, The LDH substrate is M 3+ / N 2+ -LDH or M with loaded metal 3+ / N 2 + -LDH, the M 3+ It is a trivalent metal ion, and this N 2+ It is a divalent metal ion.

9. The method of claim 8, wherein the M 3+ For Al 3+ And the N 2+ Mg 2+ .

10. The method as described in claim 8, characterized in that, M of the load metal 3+ / N 2+ -LDH is the M of the ruthenium load. 3+ / N 2 + -LDH or M with copper load 3+ / N 2+ -LDH.

11. The method as described in claim 7, characterized in that, The cyclic sugars are one or more of glucose, fructose, mannose, cellodisaccharide, galactose, maltose, fucose, and 2-deoxyglucose.

12. The method as described in claim 7, characterized in that, The collapsed LDH substrate was prepared by calcining the LDH substrate.

13. The method as described in claim 7, characterized in that, The solvent is water.

14. The method as described in claim 7, characterized in that, The reconstruction and open-loop steps are performed at a temperature above 4 degrees Celsius.

15. A method for glycoisomerization, characterized in that, include: Non-cyclic sugars are embedded in the interlayer region of a layered double hydroxide substrate (LDH substrate); as well as The acyclic sugar is converted into an isomerized sugar within the interlayer region of the LDH substrate.

16. The method as described in claim 15, characterized in that, The step of embedding the acyclic sugar into the LDH substrate is performed by equilibrating the collapsed LDH substrate and the cyclic sugar in a solvent, wherein the collapsed LDH substrate is reconstructed into the LDH substrate with a layered structure after the equilibrium is reached, so as to stabilize the acyclic sugar formed after the ring-opening of the cyclic sugar in the interlayer region.

17. The method as described in claim 16, characterized in that, The collapsed LDH substrate was prepared by calcining the LDH substrate.

18. The method as described in claim 16, characterized in that, The solvent is water.

19. The method according to any one of claims 16-18, characterized in that, The equilibrium was reached at a temperature 4 degrees Celsius above the mean.

20. The method according to any one of claims 15-18, characterized in that, The conversion of this acyclic sugar was carried out in an aqueous environment.

21. The method as described in claim 15, characterized in that, The LDH substrate is M 3+ / N 2+ -LDH or M with loaded metal 3+ / N 2+ -LDH, the M 3+ It is a trivalent metal ion, and this N 2+ It is a divalent metal ion.

22. The method as described in claim 21, characterized in that, The M 3+ For Al 3+ And the N 2+ Mg 2+ .

23. The method as described in claim 21, characterized in that, M of the load metal 3+ / N 2+ -LDH is the M of the ruthenium load. 3+ / N 2 + -LDH or M with copper load 3+ / N 2+ -LDH.

24. A method for preparing an aldol condensation product, characterized in that, include: Provides a stabilized acyclic glycoside complex according to any one of claims 1-6; as well as By mixing the stabilized acyclic sugar complex with a carbonyl active compound, the acyclic sugars in the stabilized acyclic sugar complex undergo a condensation reaction with the carbonyl active compound to form an aldol condensation product.

25. The method as described in claim 24, characterized in that, The carbonyl reactive compound is a ketone compound.

26. The method as described in claim 25, characterized in that, The carbonyl active compound is acetone.

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