无溶剂体系中酶促合成糖酯

以固定在阴离子树脂上的脂肪酶Novozym435为催化剂,在无溶剂体系中研究了果糖与月桂酸的直接酯化反应.对反应条件进行了优化,在加水量30μL、pH值7.5、月桂酸与果糖摩尔比5∶1、加酶量与底物质量比17%、温度为60℃、反应48 h,达到最大相对转化率为75.6%(以果糖月桂酸双酯计算),比不加水时的49.2%有了较大的提高.产物经TLC分析,果糖月桂酸单酯Rf值为0.44,果糖月桂酸双酯Rf值为0.79,13C NMR鉴定,产物主要是1-β-D-呋喃果糖月桂酸单酯和1,6-β-D呋喃果糖月桂酸双酯.与传统有溶剂反应相比,无溶剂反应更易于后期分离纯化,并节省了溶剂,降低了生产成本.     

紫外分光光度法测定石榴籽中葡萄糖、蔗糖和果糖

石榴籽经盐酸脱水反应后,向样品溶液中加入溴水使还原性葡萄糖氧化,与蔗糖和果糖分离;根据蔗糖难溶于乙醇,利用乙醇使蔗糖与果糖分离,据此提出了用紫外分光光度法直接测定石榴籽中葡萄糖、蔗糖和果糖含量的方法。葡萄糖、蔗糖和果糖的最大吸收波长均在285 nm处。葡萄糖、蔗糖和果糖的质量浓度在30 mg·L^-1以内服从比耳定律。方法用于石榴籽中葡萄糖、蔗糖和果糖含量的测定,测定值分别为0.203 9,0.188 6,0.373 1 mg·g^-1。测定值的相对标准偏差（n=6）均小于1.0%;加标回收率在99.4%～100.1%之间。     

化学催化葡萄糖异构化果糖

基于糖平台的生物炼制可以制备各种碳基化学品、材料和燃料.相较于葡萄糖和纤维素,果糖更容易高选择性地催化转化制备5-羟甲基糠醛等重要的生物质基平台分子,因此葡萄糖异构化果糖已经成为生物炼制过程中的重要反应步骤之一.本文详细介绍了葡萄糖经化学催化异构化果糖的反应机理,并基于异构化催化剂全面总结了近年来化学催化葡萄糖异构化果...     

由D-果糖合成新型β-氨基醇

以D-果糖为原料,经羟基保护、选择性脱保护、酯化、叠氮取代、叠氮还原为氨基反应合成了两种新型β-氨基醇,产物结构经13CNMR、1HNMR和MS确证。     

Nb-P/SBA-15催化剂的制备及其对果糖水解制5-羟甲基糠醛的催化性能

果糖催化脱水制5-羟甲基糠醛（5-HMF）是生物质转化制高附加值化合物过程中的一个重要反应。采用自制的介孔SBA-15,浸渍法制备了Nb/SBA-15催化剂,再经磷酸化处理制得Nb-P/SBA-15催化剂,研究了该催化剂在果糖脱水制5-HMF反应中的性能。SEM、TEM、BET和XRD表征结果表明,Nb/SBA-15和Nb-P/SBA-15完好地保留了SBA-15的微观结构,其内孔道直径为10 nm,铌酸在孔内表面分布均匀;负载铌和磷酸化后,孔壁变薄。NH₃-TPD结果显示,Nb/SBA-15经磷酸预处理后,不仅弱酸性位有所增加,而且产生了中强酸和强酸性位,使得在含水两相体系果糖脱水反应中,Nb-P/SBA-15比Nb/SBA-15具有更高的催化活性和5-HMF选择性。同时考察了反应温度、溶剂比例、反应时间对果糖脱水的影响,结果表明,以水/MIBK（V/V=1/2）为溶剂时,160 ℃下反应1.5 h,果糖转化率和5-HMF收率分别高达96.1%和92.6%。Nb-P/SBA-15经循环使用四次后仍具有较好的催化活性,表明该催化剂具有较高的耐水稳定性。     

分散固相萃取-高效液相色谱法测定饲料中低聚果糖含量

建立了饲料中低聚果糖的分散固相萃取-高效液相色谱分析方法。试样用50%乙腈超声提取,提取液经甲酸酸化,然后用乙二胺基-N-丙基(PSA)和石墨化碳黑(GCB)复合吸附剂净化,采用示差折光检测器进行检测。结果表明,低聚果糖在0.1~5.0mg/mL范围内具有良好的线性关系,且相关系数不小于0.9997,检出限不高于0.069mg/g。方法的加标回收率为89.9%~102%,相对标准偏差(RSD)为1.4%~4.7%。方法简单、快速,适用于饲料中低聚果糖日常检测。     

发酵液中甘露醇测定研究

用不同的显色剂,在选定的波长下,分别测量果糖发酵液中果糖和甘露醇的吸光度,葡萄糖和培养基组分对测定无干扰。甘露醇的线性回归方程为Y1=9．1X 0．0182,相关系数为0．9998,果糖的线性方程为Y2=3．23X 0．0067,相关系数为0．996。发酵液中果糖和甘露醇的吸光度有很好的叠加性．用总的吸光度减去果糖的吸光度,可快速、准确计算出甘露醇的量。     

环果糖色谱柱分离4组结构类似物

考察了聚苯乙烯键合天然环果糖色谱柱MCI Gel CRS100、硅胶键合天然环果糖色谱柱Frulic N、硅胶键合异丙基氨基甲酸酯衍生环果糖色谱柱Larihc P、硅胶键合R-萘乙基氨基甲酸酯衍生环果糖色谱柱Larihc RN在正相模式下对免疫抑制剂、维生素E、姜黄类化合物、辣椒碱4组结构类似物的分离能力。考察了固定相支撑物、固定相功能基团、流动相组成等条件对色谱分离效率的影响。结果显示MCI Gel CRS100由于其固定相较强的疏水性适用于正相色谱而不适用于亲水作用色谱。衍生化的环果糖色谱柱Larihc P和Larihc RN比天然环果糖色谱柱Frulic N具有更高的选择性。三氟乙酸的加入对环果糖色谱柱在正相色谱中分离能力的影响较小。     

D-葡萄糖D-果糖与硼的有机物形成配合物的稳定性研究

葡萄糖异构酶加速葡萄糖与果糖的平衡,平衡时果糖含量为42％左右,体系中加入一些硼酸盐,果糖的含量提高到80％左右,究其原因可能是由于葡萄糖和果糖与硼酸盐形成不同稳定性的配合物。虽然Roy,Conner,Daris,Belcher,Lorand等都已报导了这些配合物的稳定常数,概括结果分歧较大。Belcher曾首次报导了硼酸与D-果糖的配位数为     

小鼠肝果糖6-磷酸,2-激酶的纯化及动力学研究

经过超离心,聚乙二醇分级沉淀及DEAE-Sephadex,Blue-Sepbarose。磷酸纤维素三种柱层析等一系列过程,纯化了小白鼠肝脏的果糖6-磷酸,2-激酶。经凝胶过滤和SDS聚丙烯酰胺电泳方法测出该酶是由两个相同亚基构成的分子量为110000的蛋白。Mg~(2+)是其活性所必需的,活化方式呈正协同性。酶与底物的结合方式,对果糖6-磷酸表现正协同性,对ATP无协同性,其Km值随果糖6-磷酸的浓度减小而增大,表明酶的作用为顺序机制。活性中心有一个必需氨基酸残基与结合ATP有关,结合后,其侧链pKa由9.5移至9.8。     

In situ kinetic study on hydrothermal transformation of D-glucose into 5-hydroxymethylfurfural through D-fructose with 13C NMR

Kinetics of hydrothermal reaction of D-glucose was investigated at 0.02 M over a temperature range of 120-160 °C by applying in situ (13)C NMR spectroscopy. D-Glucose was found to be reversibly transformed first into D-fructose (intermediate) and successively into 5-hydroxymethylfurfural (5-HMF) through dehydration. The carbon mass balance has been kept within the detection limit, and no other reaction pathways are present. The hydrothermal reaction of d-glucose is thus understood as that of D-fructose in the sense that the D-glucose reaction proceeds only through D-fructose. All the isomers of D-glucose and D-fructose were detected by the in situ (13)C NMR in D(2)O: they are the open chains and the pyranoses and furanoses of α- and β-types. The β-forms are the most stable due to the hydration. For both D-glucose and D-fructose, the isomers are in a rapid equilibrium for each monosaccharide, and they are treated collectively in the kinetic analysis of the slower hydrothermal reactions. The reactions are of the first order with respect to the concentrations of D-glucose and D-fructose, and D-glucose converts to 5-HMF on the order of hours. The kinetic parameters were determined by the in situ method.     

Studies on mechanism of reaction and density behavior during anhydrous D-fructose mutarotation in the supercooled liquid state

Recently, we have studied the mutarotation kinetics in D-fructose by means of dielectric spectroscopy. In the present work we investigate density behavior of D-fructose during mutarotation process. By performing volume measurements at temperature T = 303 K and pressure p = 10 MPa we are able to monitor kinetics of this process. As a result we found nearly the same value of the rate constant as previously determined from dielectric measurements. However, these two experimental methods monitor different molecular aspects of mutarotation phenomenon in D-fructose. Dielectric spectroscopy is sensitive to the decay of former ring as well as to the forming of another, while specific volume measurements are sensitive to the forming of new tautomers only. Calculations of activation energy of mutarotation in D-fructose led us to the conclusion, that mechanism of this reaction in amorphous phase could be based on internal proton transfer. Moreover it was found that the main mutarotation path in quenched D-fructose melt is transformation of α,β-furanose to β-pyranose.     

Alkaline Degradation of Monosaccharides VI1: The Fhucto-Fobmose Reaction of Mixtures of D-Fructose and Formaldehyde

The final product compositions of the alkaline (calcium hydroxide) degradation of D-fructose in the presence of formaldehyde at several D-fructose/formaldehyde ratios, and of the formose reaction were determined by HPLC and GC analysis. At decreasing D-fructose/formaldehyde ratio a gradual change of the composition was observed except for lactic acid and the oligomeric acidic products, which show a minimum and a maximum, respectively. A mechanistic explanation is given by the aldolization of formaldehyde both with saccharides and with their subsequent α-dicarbonyl intermediates, which favours the formation of oligomeric products at the cost of lactic acid. It is established both experimentally and theoretically that there is no essential mechanistic difference between the formose reaction and the alkaline degradation of monosaccharides.     

Immobilization of pig muscle aldolase on a silica-based support

Pig muscle aldolase was covalently attached to a silica-based support possessing aldehyde functional groups. The activity of the immobilized enzyme was 37 U/g solid, and the specific activity calculated on a bound protein basis was 1.9 U/mg protein. The optimum pH for the catalytic activity was pH 7.5. The apparent optimum temperature was found to be 45 degrees C. The Km app value of the immobilized aldolase with D-fructose 1,6-diphosphate as substrate was 1.25 X 10(-4) M. The conformational stability was improved by the immobilization. The immobilized aldolase was used for the continuous splitting of D-fructose 1,6-diphosphate.     

Qualitative and quantitative evaluation of mono- and disaccharides in D-fructose, D-glucose and sucrose caramels by gas-liquid chromatography-mass spectrometry. Di-D-fructose dianhydrides as tracers of caramel authenticity.

The monosaccharide (D-fructose, D-glucose, anhydrosugars), disaccharide (glucobioses) and pseudodisaccharide (di-D-fructose dianhydrides) content of D-fructose, D-glucose and sucrose caramels has been determined by gas-liquid chromatography-mass spectrometry (GLC-MS) of their trimethylsilyl (TMS) or TMS-oxime derivatives. The chromatographic profiles revealed significant differences in the disaccharide/pseudodisaccharide distribution depending on the caramel source: a D-fructose caramel contains prominent proportions of di-D-fructose dianhydrides, a D-glucose caramel mainly D-glucobioses, and a sucrose caramel similar proportions of both disaccharide/pseudodisaccharide series. It is noteworthy that di-D-fructose dianhydrides are found in all three types of caramels and might then be used as specific tracers of the authenticity of caramel, i.e., a product resulting from the controlled heat treatment of food-grade carbohydrates for use as food additives.     

Ni(Ii)-Catalysed Reactions of Free D-Fructose Derivatives Modified at Positions C-5 and/or C-6

Abstract

The nickel(II) catalysed isomerisation reactions of D-fructose derivatives modified at positions 5 and/or 6 were investigated. 5,6-Dimodified open-chain D-fructose derivatives as well as an open-chain derivative of D-xylulose reacted to give complex mixtures containing no major product. 5-Modified ketohexoses invariantly were degraded to the corresponding methyl pentonates upon loss of C-1. 6-Modified D-fructofuranose furnished the desired rearrangement into a branched-chain derivative of D-ribose. In marked contrast to previous belief, from these results it appears that 5-OH plays an important role in the productive co-ordination of the D-fructose derivatives to the nickel-ethylenediamine complexes under consideration.     

Sustainable Synthesis of 2-Hydroxymethylbenzimidazoles using D-Fructose as a C2 Synthon

D-fructose, a biomass-derived carbohydrate has been identified as an environmentally benign C₂ synthon in the preparation of synthetically useful 2-hydroxymethylbenzimidazole derivatives by coupling with 1,2-phenylenediamines. Proof of concept was established by synthesizing 23 examples using BF₃.OEt₂ (20 mol%), TBHP (5.5 M, decane) (1.0 equiv.) in CH₃CN at 90 °C for 1 h. The pivotal features of this method include metal-free conditions, short time, good functional group tolerance, gram scale feasibility and the synthesis of benzimidazole fused 1,4-oxazine. Control studies with conventional C₂ synthons did not produce the desired product, thus suggesting a new reaction pathway from D-fructose.     

Facile synthesis of stable cubic mesoporous silica SBA-1 over a broad temperature range with the aid of D-fructose

A highly ordered cubic mesoporous silica SBA-1 with enhanced stability towards washing with water has been synthesized simply by adding D-fructose as an auxiliary agent during the synthesis.     

茜素红S-硼酸体系对单糖的双光谱识别

利用硼酸与茜素红S和糖中的邻二羟基可逆结合的特点,以硼酸为中介运用竞争结合作用机理构建单糖分析法.在pH7.4的KH2PO4-NaOH缓冲溶液中,茜素红S作为指示剂与硼酸结合生成ARS-BA配合物,其结合常数为5.09×102L/mol.糖与指示剂ARS竞争结合硼酸使指示剂游离出来,产生明显的颜色变化,据此建立糖的识别方法.考察了D-葡萄糖、D-山梨醇、D-半乳糖、D-甘露糖、D-果糖、D-阿拉伯糖和L-阿拉伯糖对上述ARS-BA体系光谱的影响.结果显示:该体系对D-山梨醇和D-果糖有较好的光谱响应,其光谱变化灵敏度依D-山梨醇＞D-果糖＞D-阿拉伯糖～D-半乳糖＞D-葡萄糖＞D-甘露糖＞L-阿拉伯糖之序.     

Study of viscometric properties of L-ascorbic acid in binary aqueous mixtures of D-glucose and D-fructose

The relative viscosities and activation parameters of L-ascorbic acid have been determined in water and binary aqueous mixtures of D-glucose and D-fructose at different temperatures. A and B-coefficients of Jones–Dole equation are determined using density and viscosity data. Gibbs energy of activation of viscous flow per mole of solvent as well as per mole of solute along with activation enthalpy and entropy is also determined using Feakin’s transition-state theory. The obtained results are explained in terms of intermolecular interactions and in this study L-ascorbic acid has been found as structure breaker in binary aqueous mixtures of D-glucose and D-fructose.