Isomerisation of aldoses in pyridine in the presence of aluminium oxide
摘要:
Addition of aluminium oxide to boiling pyridine solutions Of D-xylose, L-arabinose, D-mannose and D-glucose strongly increased the reaction rate of the aldose-ketose transformation. The maximum content of 2-ketose was reached after less than 2 h for the aldopentoses and 3 h for the aldohexoses. D-threo-2-Pentulose (xylulose) was prepared from D-xylose, and isolated as its O-isopropylidene derivative, the yield was nearly twice that compared to that usually obtained in the classical Lobry de Bruyn-Alberda van Ekenstein transformation in pyridine. (C) 2004 Elsevier Ltd. All rights reserved.
Here we have characterized the first transketolase (TK) from a thermophilic microorganism, Geobacillus stearothermophilus, which was expressed from a synthetic gene in Escherichia coli. The G. stearothermophilus TK (mTKgst) retained 100% activity for one week at 50 °C and for 3 days at 65 °C, and has an optimum temperature range around 60–70 °C, which will be useful for preparative applications and
Broadening Deoxysugar Glycodiversity: Natural and Engineered Transaldolases Unlock a Complementary Substrate Space
作者:Madhura Rale、Sarah Schneider、Georg A. Sprenger、Anne K. Samland、Wolf-Dieter Fessner
DOI:10.1002/chem.201002942
日期:2011.2.25
inaccessible by available enzymes, from a [3×8] substrate matrix. Although aliphatic and hydroxylated aliphatic aldehydes were good substrates, D‐lactaldehyde was found to be an inhibitor possibly as a consequence of inactive substratebinding to the catalytic Lys residue. A 1‐hydroxy‐2‐alkanone moiety was identified as a common requirement for the donor substrate, whereas propanone and butanone were inactive
Ketosylamin‐Umlagerung bei der Umsetzung von
<scp>D</scp>
‐
<i>threo</i>
‐Pentulose (
<scp>D</scp>
‐Xylulose) mit α‐Aminosäuren
作者:Kurt Heyns、Wolfgang Beilfuß
DOI:10.1002/cber.19701030925
日期:1970.9
D-threo-Pentulose (1) reagiert mit Glycin (2a), L-α-Alanin (2b) oder L-Valin (2c) zum Gemisch der D-Xylose-und D-Lycxose-Aminosäuren, aus dem sich durch Säulenchromatographie die D-Xylose-aminosäuren (4a–c) rein gewinnen lassen. 2-L-α-Alanino-2-desoxy-D-lyxose (5b) und 2-L-Valino-2-desoxy-D-lyxose (5c) werden durch Kristallisation erhalten. Die Reaktion der D-Xylulose (1) mit Glycin (2a) wird quantitativ
D-苏式-戊糖(1)瑞格特mit甘氨酸(2a),L-α-丙氨酸(2b)或L-Valin(2c)zum Gemisch der D-木糖和D-Lycxose-Aminosäuren D-木糖-氨基脲(4a–c)盖文·拉森(rewin gewinnen lassen)。2 -L-α-丙氨酸-2-脱氧-D-lyxose(5b)和2 -L-Valino-2-脱氧-D-lyxose(5c)werden durch Kristallisation erhalten。D-木酮糖(1)与甘氨酸(2a)结合定量检测。
Synthesis of Furfural from Xylose, Xylan, and Biomass Using AlCl3⋅6 H2O in Biphasic Media via Xylose Isomerization to Xylulose
作者:Yu Yang、Chang-Wei Hu、Mahdi M. Abu-Omar
DOI:10.1002/cssc.201100688
日期:2012.2.13
activity or selectivity for furfural. Extension of this biphasic reaction system to include xylan as the starting material afforded furfural in 64 % yield. The use of corn stover, pinewood, switchgrass, and poplar gave furfural in 55, 38, 56, and 64 % yield, respectively, at 160 °C. Even though AlCl3⋅6 H2O did not affect the conversion of crystalline cellulose, moderate yields of the by‐product 5‐hydroxymethylfurfural
糠醛在从木糖在含有的AlCl一个水-四氢呋喃双相介质中的反应高收率(75%),制备3 ⋅ 6 H 2 O和NaCl的微波下在140℃加热。反应曲线表明,木酮糖的形成是通往脱水产物(糠醛)的中间产物。在这些条件下,反应在45分钟内完成。含的AlCl水相3 ⋅ 6 H 2O和NaCl可以循环使用多次(> 5),而对糠醛的活性或选择性没有任何损失。将该双相反应体系扩展到包括木聚糖作为起始原料,糠醛的收率为64%。在160°C下,使用玉米秸秆,松木,柳枝switch和杨树的糠醛收率分别为55%,38%,56%和64%。即使的AlCl 3 ⋅ 6 H 2 ö不影响结晶纤维素的转化中,副产物5-羟甲基糠醛(HMF)的中等产率指出。从松木中获得最高42%的HMF收率。HMF和糠醛从生物质中的联产是由于半纤维素水解导致生物质中纤维素网络的减弱。AlCl 3的多功能容量⋅6 H 2 O(半纤维素水解,木糖异
Modified Versions of AM‐4 for the Aqueous Phase Isomerization of Aldo‐Saccharides
作者:Margarida M. Antunes、Auguste Fernandes、M. Filipa Ribeiro、Zhi Lin、Anabela A. Valente
DOI:10.1002/ejic.202000038
日期:2020.5.10
The isomerization of aldo‐saccharides to keto‐saccharides is an important transformation in biomass conversion processes. The use of eco‐friendly heterogeneous catalysts for these reactions is most attractive, albeit good catalytic stability continues a challenge. The as‐synthesized Aveiro‐Manchester material number 4 (AM‐4, Na3(Na,H)Ti2O2[Si2O6]2,2H2O) possessed isomerization activity, but limited