74801-06-2Relevant academic research and scientific papers
Molecular-Level Understanding of the Major Fragmentation Mechanisms of Cellulose Fast Pyrolysis: An Experimental Approach Based on Isotopically Labeled Model Compounds
Yu, Zaikuan J.,Easton, McKay W.,Murria, Priya,Xu, Lan,DIng, Duanchen,Jiang, Yuan,Zhang, Jifa,Kentt?maa, Hilkka I.
, p. 7037 - 7050 (2019/06/14)
Evaluation of the feasibility of various mechanisms possibly involved in cellulose fast pyrolysis is challenging. Therefore, selectively 13C-labeled cellotriose, 18O-labeled cellobiose, and 13C- and 18O-doubly-labeled cellobiose were synthesized and subjected to fast pyrolysis in an atmospheric pressure chemical ionization source of a linear quadrupole ion trap/orbitrap mass spectrometer. The initial products were immediately quenched, ionized using ammonium cations, and subsequently analyzed using the mass spectrometer. The loss or retention of isotope labels upon pyrolysis unambiguously revealed three major competing mechanisms - sequential losses of glycolaldehyde/ethenediol molecules from the reducing end (the reducing-end unraveling mechanism), hydroxymethylene-assisted glycosidic bond cleavage (HAGBC mechanism), and Maccoll elimination. Important discoveries include the following: (1) Reducing-end unraveling is the predominant mechanism occurring at the reducing end; (2) Maccoll elimination facilitates the cleaving of aglyconic bonds, and it is the mechanism leading to formation of reducing carbohydrates; 3) HAGBC occurs for glycosides but not at the reducing end of cellodextrins; 4) HAGBC and water loss are the predominant reactions for fast pyrolysis of 1,6-anhydrocellodextrins; and 5) HAGBC can proceed after reducing-end unraveling but unraveling does not occur once the HAGBC reaction pathway is initiated. Moreover, hydrolysis was conclusively ruled out for fast pyrolysis of cellobiose, cellotriose, and 1,6-anhydrocellodextrins up to cellotetraosan. No radical reactions were observed.
A strategy for chemical synthesis of selectively methyl-esterified oligomers of galacturonic acid
Clausen, Mads H.,Jorgensen, Malene R.,Thorsen, Jesper,Madsen, Robert
, p. 543 - 551 (2007/10/03)
The synthesis of monomethyl-esterified trigalacturonans 1-3 is described as part of a general strategy towards pectic oligosaccharides. The necessary monomeric building blocks were all prepared on a large scale from galactose pentaacetate. The glycosylations were carried out between galactose glycosyl donors and acceptors using the n-pentenyl glycosylation technique. Yields of the desired α-anomers were in the 50 to 74% range. The trigalactans thus obtained were then subjected to oxidation at C-6. Depending on the protecting group at this position the oxidation either produced the carboxylic acid or the corresponding methyl ester. Hereby, oligomers of galacturonic acid can be prepared with methyl esters introduced in a regiocontrolled fashion.
Anchimeric assistance by the anomeric phenylthio group in the nucleophilic substitution of a 6-O-trifluoromethanesulfonyl-β-D-galactopyranoside
Compain-Batissou, Muriel,Mesrari, Lamya,Anker, Daniel,Doutheau, Alain
, p. 201 - 205 (2007/10/03)
Nucleophilic displacement by the cyanide anion of the 6-O-triflyl group in phenyl 6-O-triflyl-2,3-di-O-benzyl-4-O-p-methoxybenzyl-1-thio-β-D-galactopyranoside takes place via an intermediate 1,6-sulfonium salt resulting from the anchimeric assistance of the C-1 phenylthio group. Copyright (C) 1999 Elsevier Science Ltd.
A Mild Procedure for the Regiospecific Benzylation and Allylation of Polyhydroxy-compounds via their Stannylene Derivatives in Non-polar Solvents
David, Serge,Thieffry, Annie,Veyrieres, Alain
, p. 1796 - 1801 (2007/10/02)
The reactions of benzyl and allylbromides on the stannylene derivatives of polyhydroxy-compounds, which normally proceed only at insignificant speed in refluxing benzene solution, are greatly accelerated in the presence of quaternary ammonium halides.Thes
