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Titanium-Beta Zeolites Catalyze the Stereospecific Isomerization of D-Glucose to L-Sorbose via Intramolecular C5–C1 Hydride Shift

Gounder, Rajamani and Davis, Mark E. (2013) Titanium-Beta Zeolites Catalyze the Stereospecific Isomerization of D-Glucose to L-Sorbose via Intramolecular C5–C1 Hydride Shift. ACS Catalysis, 3 (7). pp. 1469-1476. ISSN 2155-5435. doi:10.1021/cs400273c.

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Pure-silica zeolite beta containing Lewis acidic framework Ti^(4+) centers (Ti-Beta) is shown to catalyze the isomerization of D-glucose to L-sorbose via an intramolecular C5–C1 hydride shift. Glucose–sorbose isomerization occurs in parallel to glucose–fructose isomerization on Ti-Beta in both water and methanol solvents, with fructose formed as the predominant product in water and sorbose as the predominant product in methanol (at 373 K) at initial times and over the course of >10 turnovers. Isotopic tracer studies demonstrate that ^(13)C and D labels placed respectively at the C1 and C2 positions of glucose are retained respectively at the C6 and C5 positions of sorbose, consistent with its formation via an intramolecular C5–C1 hydride shift isomerization mechanism. This direct Lewis acid-mediated pathway for glucose–sorbose isomerization appears to be unprecedented among heterogeneous or biological catalysts and sharply contrasts indirect base-mediated glucose–sorbose isomerization via 3,4-enediol intermediates or via retro-aldol fragmentation and recombination of sugar fragments. Measured first-order glucose–sorbose isomerization rate constants (per total Ti; 373 K) for Ti-Beta in methanol are similar for glucose and glucose deuterated at the C2 position (within a factor of ~1.1), but are a factor of ~2.3 lower for glucose deuterated at each carbon position, leading to H/D kinetic isotope effects expected for kinetically relevant intramolecular C5–C1 hydride shift steps. Optical rotation measurements show that isomerization of D-(+)-glucose (92% enantiomeric purity) with Ti-Beta in water (373 K) led to the formation of L-(−)-sorbose (73% enantiomeric purity) and D-(−)-fructose (87% enantiomeric purity) as the predominant stereoisomers, indicating that stereochemistry is preserved at carbon centers not directly involved in intramolecular C5–C1 or C2–C1 hydride shift steps, respectively. This new Lewis acid-mediated rearrangement of glucose to sorbose does not appear to have a metalloenzyme analog.

Item Type:Article
Related URLs:
URLURL TypeDescription DOIArticle
Gounder, Rajamani0000-0003-1347-534X
Davis, Mark E.0000-0001-8294-1477
Additional Information:© 2013 American Chemical Society. Received: April 11, 2013; Revised: May 15, 2013; Published: May 20, 2013. This work was financially supported as part of the Catalysis Center for Energy Innovation, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award No. DESC0001004. We thank Prof. Brian M. Stoltz (Caltech) for use of the optical polarimeter.
Funding AgencyGrant Number
Catalysis Center for Energy InnovationUNSPECIFIED
Department of Energy (DOE) Office of Science, Office of Basic Energy SciencesDE-SC0001004
Subject Keywords:fructose, glucose, hydride shift, isomerization, Lewis acid, sorbose, stereospecific, titanium-Beta
Issue or Number:7
Record Number:CaltechAUTHORS:20130903-155918546
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Official Citation:Titanium-Beta Zeolites Catalyze the Stereospecific Isomerization of d-Glucose to l-Sorbose via Intramolecular C5–C1 Hydride Shift Rajamani Gounder and Mark E. Davis ACS Catalysis 2013 3 (7), 1469-1476
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:41071
Deposited By: Tony Diaz
Deposited On:04 Sep 2013 21:54
Last Modified:10 Nov 2021 04:25

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