Polymer-mediated cyclodehydration of alditols and ketohexoses
摘要:
The polymer PEDOT+ (1 or 2) mediates a cyclodehydration reaction with alditols 3, 5, 7, 9, in hydrocarbon solvents, to give cyclic ethers 4, 6, 8, or 10, respectively, in high yield with a trivial isolation protocol. Polymers 1 or 2 also mediate the cyclodehydration of ketohexoses such as D-fructose, but not aldohexoses, to the important industrial intermediate 5-hydroxymethylfurfural (17), under milder conditions when compared to reactions mediated by mineral acids. A cascade reaction with ketohexoses is observed in toluene via cyclodehydration followed by Friedel-Crafts alkylation of the initially formed benzylic alcohol to give 16. (C) 2011 Elsevier Ltd. All rights reserved.
Kiliani reactions on ketoses: branched carbohydrate building blocks from D-tagatose and D-psicose
作者:Raquel Soengas、Ken Izumori、Michela Iezzi Simone、David J. Watkin、Ulla P. Skytte、Wim Soetaert、George W.J. Fleet
DOI:10.1016/j.tetlet.2005.06.030
日期:2005.8
D-Tagatose and D-psicose on treatment with sodium cyanide gave mixtures of branched sugar lactones; extraction of the crude products by acetone in the presence of acid permits direct access to branched carbohydrate diacetonides, likely to be of value as new chirons. In both cases, the major lactone products—diacetonides with a 2,3-cis-diol relationship—can be crystallised in around 40–50% yield from
Convergent
<i>in situ</i>
Generation of Both Transketolase Substrates
<i>via</i>
Transaminase and Aldolase Reactions for Sequential One‐Pot, Three‐Step Cascade Synthesis of Ketoses
We describe an efficient three‐enzyme, sequential one‐pot cascade reaction where both transketolase substrates are generated in situ in a convergent fashion. The nucleophilic donor substrate hydroxypyruvate was obtained from l‐serine and pyruvate by a transaminase‐catalyzed reaction. In parallel, three different (2S)‐α‐hydroxylated aldehydes, l‐glyceraldehyde, d‐threose, and l‐erythrose, were generated
Stereoselective preparations of protected rare sugars and derivatives, namely l-psicose, l-altritol, and l-talose have been achieved in 70, 44, and 18% yield, respectively, from an orthogonallyprotected l-glyceraldehyde derivative. The key step is the stereoselective proline-catalyzed aldol reaction of this aldehyde with dioxanone. Stereoselective preparations of protected rare sugars and derivatives
a multienzyme cascadereaction with continuous chromatography, realized as simulated moving bed chromatography, to overcome the intrinsic yield limitation. Efficient production of D‐psicose from sucrose in a three‐step cascadereaction using invertase, D‐xylose isomerase, and D‐tagatose epimerase, via the intermediates D‐glucose and D‐fructose, is described. This set‐up allowed the production of pure
One-pot, two-step cascade synthesis of naturally rare<scp>l</scp>-erythro (3S,4S) ketoses by coupling a thermostable transaminase and transketolase
作者:Marion Lorillière、Maxime De Sousa、Felipe Bruna、Egon Heuson、Thierry Gefflaut、Véronique de Berardinis、Thangavelu Saravanan、Dong Yi、Wolf-Dieter Fessner、Franck Charmantray、Laurence Hecquet
DOI:10.1039/c6gc02015a
日期:——
An efficient simultaneous cascade of two enzymatic steps catalyzed by thermostable transaminase and transketolase was performed at elevated temperature allowing the synthesis of naturally rare L-erythro (3S,4S) ketoses. L-ribulose, 5-deoxy-L-ribulose,...