排序方式: 共有13条查询结果,搜索用时 187 毫秒
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Isidoro Izquierdo Cubero Maria T. Plaza López-Espinosa Rafael Acuña Castillo 《Journal of chemical ecology》1992,18(2):115-125
The synthesis of (3S,6R)-3-hydroxy-1,7-dioxaspiro[5.5]undecane (8) and its (4R)-4-hydroxy isomer (11) from (3R,4S,6R)-3,4-dihydroxy-1,7-dioxaspiro[5.5]undecane (1), obtained from D-fructose, has been accomplished by regioselective deoxygenation at C-4 and C-3, respectively, of the appropriately protected derivatives.Enantiospecific synthesis of spiroacetals. Part III. For Part II, see Izquierdo et al. (1991). 相似文献
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A novel CoAl-hydrotalcite catalyst with different Co2+/Al3+ ratios was facilely synthesized using a modified coprecipitation method. Different techniques such as X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) were used to characterize the resultant CoAl-hydrotalcite. It was indicated that high crystallinity and a single-phase, layered structure with good composition was successfully fabricated. The resultant CoAl-hydrotalcite catalysts and two comparative hydrotalcites (ZnAl-HT and NiAl-HT) were employed for the selective dehydration of D-fructose into platform chemical 5-hydroxymethylfurfural (HMF), which is a versatile intermediate for the production of biofuels and value-added chemicals. It was shown that the metal variation in Co2+/Al3+ ratios and reaction temperature display clear influence on the catalytic activities. Furthermore, the spent CoAl-hydrotalcite catalysts were easily recycled and show high catalytic stability over three consecutive runs. [Supplementary materials are available for this article. Go to the publisher's online edition of Chemical Engineering Communications for the following free supplemental resources: Table S1 and Figure S1.] 相似文献
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ABSTRACT: D-psicose has been implicated in glycemic control in recent animal and human studies. In this study, the effects of D-psicose on glycemic responses, insulin release, and lipid profiles were compared with those of D-glucose and D-fructose in a genetic diabetes model. C57BL/6J db/db mice were orally supplemented with 200 mg/kg BW of D-psicose, D-glucose, or D-fructose, respectively, while diabetes control or wild type mice were supplemented with water instead. D-psicose sustained weight gain by about 10% compared to other groups. The initial blood glucose level maintained from 276 to 305 mg/dL during 28 d in the D-psicose group, whereas a 2-fold increase was found in other groups (P < 0.05) among diabetic mice. D-psicose significantly improved glucose tolerance and the areas under the curve (AUC) for glucose among diabetes (P < 0.05), but had no effect on serum insulin concentration. The plasma lipid profile was not changed by supplemental monosacchrides, although the ratio of LDL-cholesterol/HDL-cholesterol was ameliorated by D-psicose. The administration of D-psicose reversed hepatic concentrations of triglyceride (TG) and total cholesterol (TC) by 37.88% and 62.89%, respectively, compared to the diabetes control (P < 0.05). The current findings suggest that D-psicose shows promise as an antidiabetic and may have antidyslipidemic effects in type 2 diabetes. 相似文献
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该研究利用含有组成型启动子的质粒pET-20b载体,在大肠杆菌(Escherichia coli)BL21(DE3)中对3种D-阿洛酮糖3-差向异构酶进行异源表达,其后以D-果糖为底物进行静息细胞转化。结果表明,重组菌在摇床30 ℃、200 r/min转速下发酵48 h,能够利用D-果糖为底物生产D-阿洛酮糖,转化率分别达到27.56%、23.99%和25.98%。为降低D-果糖对D-阿洛酮糖纯化过程中的影响,在产糖的过程后偶联酿酒酵母(Saccharomyces cerevisiae)好氧发酵过程,消耗掉混合糖液中的D-果糖,结果显示转化24 h后D-果糖去除率达到94.22%,该研究为下游D-阿洛酮糖的分离和纯化提供了新的思路。 相似文献
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以含有丰富金属离子的造纸污泥为原料,通过高温煅烧法制备生物炭(SBC),并与对氨基苯磺酸进行接枝,制备了一种高效碳基固体酸催化剂(S-SBC)。通过FTIR、XRD、SEM等对催化剂的组成、形貌、结构、酸负载量、比孔径及比表面积等进行表征。将该催化剂用于D-果糖转化为5-羟甲基糠醛(HMF)反应,对反应时间、反应温度、催化剂用量及溶剂种类、D-果糖质量分数等影响因素进行考察,并与用杨木为原料且采用相同方法制备的杨木炭催化剂(S-PBC)进行比较,结果表明,S-SBC的催化活性优于S-PBC。S-SBC同时含有由金属离子形成的Lewis酸位点以及—SO3H等形成的Brönsted酸位点,两种酸位点在催化D-果糖脱水制备5-羟甲基糠醛的过程中具有协同作用。S-SBC在二甲基亚砜中130 ℃下催化反应40 min, HMF收率高达95.2%。连续使用4次后,催化活性没有明显下降。 相似文献
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以D-果糖为原料,经过内酯化反应、酰化、羰基还原、再次酰化4步反应合成2-C-甲基-α-D-呋喃核糖四苯甲酸酯(化合物 d),总收率为10.60%。采用1H-NMR、13C-NMR和MS等方法对中间产物和目标产物进行了结构表征。在2-C-甲基-D-核糖酸-1,4-内酯(a)的合成中,结合反应条件确定了最佳原料为D-果糖和氧化钙;通过对还原剂剂硼氢化钠﹑四氢化铝锂和红铝的比较,得出红铝为中间体2,3,5-三苯甲酰氧基-2-C-甲基-βD-呋喃核糖(c)合成的较优还原剂,还原收率可达96.20%;通过单因素考察确定三乙胺作为酰化反应的缚酸剂,酰化收率可达75.84%。 相似文献
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基于高碘酸钠氧化果糖产生甲醛,甲醛与酚试剂反应生成绿蓝色有机物,此产物在630nm处有最大吸收,建立了果糖的检测方法。实验采用单因素法探索了氧化和显色反应的最佳条件,并对其氧化和显色机理进行了探讨。 相似文献
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Komla Sanda Luc Rigal Antoine Gaset 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》1992,55(2):139-145
A stepwise method for the conversion of D-fructose into 5-chloromethyl-2-furancarboxaldehyde is described. The sugar was first subjected to acid-catalysed dehydration in N,N-dimethylformamide to give 5-hydroxymethyl-2-furancarboxaldehyde as an intermediate. The latter was then chlorinated in situ with phosphorylchloride, to give the named chloro-compound in an 85% overall yield, in the absence of any humic matter or tarry product. 相似文献