Gas-Phase Intercluster Thiyl-Radical Induced C–H Bond Homolysis Selectively Forms Sugar C2-Radical Cations of Methyl D-Glucopyranoside: Isotopic Labeling Studies and Cleavage Reactions
作者:Sandra Osburn、Gaetano Speciale、Spencer J. Williams、Richard A. J. O’Hair
DOI:10.1007/s13361-017-1667-2
日期:2017.7.1
exchangeable OH and NH protons with deuterons reveals that the sugar radical cation is formed in a process involving abstraction of a hydrogenatom from a C-H bond of the sugar coupled with proton transfer to the sugar, to form [M - H• + D+]. Investigation of this process using individual C-D labeled sugars reveals that the main site of H/D abstraction is the C2 position, since only the C2-deuterium
一组甲基D-吡喃葡萄糖苷的同位素异构体与多级质谱实验结合使用,以确定通过最近开发的“生物启发”方法形成的糖自由基阳离子的自由基位点和裂解反应。在CID(MS2)的第一阶段,糖和S-亚硝基半胱胺[H3NCH2CH2SNO + M] +之间的质子化非共价复合物的碰撞诱导解离(CID)通过键均解释放硫代自由基,得到非共价自由基阳离子,[H3NCH2CH2S•+ M] +。该自由基阳离子复合物的CID(MS3)导致非共价复合物解离,生成糖自由基阳离子。用氘核取代所有可交换的OH和NH质子表明,糖自由基阳离子是在一个过程中形成的,该过程涉及从糖的CH键中夺取氢原子,然后将质子转移到糖中,从而形成[M-H•+ D +]。使用单个CD标记的糖对此过程进行的研究表明,H / D提取的主要位点是C2位置,因为只有C2氘标记的糖会产生占主导地位的[M-D•+ H +]产物离子。通过另一阶段的CID(MS4)研究了二糖糖基阳离子[M-H•+
Synthesis of<sup>13</sup>C-Labeled Biosynthetic Precursor of Lipid A and Its Analogue with Shorter Acyl Chains
The synthesis of regiospecifically 13C-labeled compounds of a biosynthetic precursor of lipid A and its analogue with shorter acyl chains is described. d-(6-13C)Glucose was converted into a suitably protected glucosamine derivative via 1,6-anhydro-β-d-(6-13C)glucose. After coupling with glycosyl donors, the desired compounds were synthesized through a 6-step reaction sequence. The total yields were 1.7% for the biosynthetic precursor, and 6.4% for the short acyl analogue, respectively, for a total of 18 steps from d-(6-13C)glucose.
Mechanism of Brønsted Acid-Catalyzed Glucose Dehydration
作者:Liu Yang、George Tsilomelekis、Stavros Caratzoulas、Dionisios G. Vlachos
DOI:10.1002/cssc.201403264
日期:2015.4.24
the rate‐limiting step is the first dehydration of protonated glucose and that the majority of glucose is consumed through the HMF intermediate. We introduce a combination of 1) automatic mechanism generation with isotopic tracing experiments and 2) elementary reaction flux analysis of important paths with NMR spectroscopy and kinetic experiments to assess mechanisms. We find that the excess formic acid
[1-(13)C], [2-(13)C] and [6-(13)C] D-glucose were, respectively, ozonized in a semi-batch reactor in acidic and basic conditions. The composition of the gas phase was evaluated by on-line mass spectrometry measurements. The quantitative and isotopic analyses of the carbon dioxide formedduring ozonization are presented and discussed. The data, correlated with previous literature results, clearly show
Carbon Exchange in Hot Alkaline Degradation of Glucose
作者:Amanda V. Ellis、Michael A. Wilson
DOI:10.1021/jo025912t
日期:2002.11.1
The decomposition of 1-C-13-D-glucose, 6-C-13-D-glUeose, and 1-C-13-sodium lactate has been studied in hot (145+/-3 degreesC) alkaline (3.5 M) sodium hydroxide solution in order to understand the mechanisms of carbon exchange in the alkaline degradation of glucose. The results show that in the formation of lactate from glucose the carboxylate (COO-) carbon is formed preferentially from C1 carbons but methyl (CH3) carbon is formed preferentially from C6 carbons. However, on further decomposition of lactate to ethanol and carbonate, C-13-labeled carboxylate (COO-) is scrambled equally among carbonate and both carbons in product ethanol molecules. In the production of glycolate, the labeled C1 carbon mainly ends up as carboxylate (COO-) carbon, while for C6-labeled glucose the labeled carbon mainly ends up as alcoholic (CH2OH) carbon. In the production of acetate and formate there is also discrimination between C1 and C6 label.