Improvement of gold-catalyzed oxidation of free carbohydrates to corresponding aldonates using microwaves

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1 Supplementary Information Improvement of gold-catalyzed oxidation of free carbohydrates to corresponding aldonates using microwaves Mehdi Omri, a Gwladys Pourceau, *,a Matthieu Becuwe b and Anne Wadouachi *,a a. Laboratoire de Glycochimie, des Antimicrobiens et des Agroressources (LG2A) UMR CNRS Institut de Chimie de Picardie FR 3085, Université de Picardie Jules Verne, 33 rue Saint Leu, FR Amiens Cedex, France. gwladys.pourceau@u-picardie.fr; anne.wadouachi@u-picardie.fr b. Laboratoire de Réactivité et Chimie des Solides (LRCS), UMR CNRS Institut de Chimie de Picardie FR 3085, Université de Picardie Jules Verne, 33 rue Saint Leu, FR Amiens Cedex, France Number of pages: 12 Number of figures: 9 Number of table: 0 Contents Materials... S2 Instruments... S2 Catalysts characterization... S3 XRD analysis... S3 TEM analysis... S5 Conversion rate determination... S5 Oxidation of glucose using MW-assisted procedure depending on the catalyst... S8 Gold content influence... S9 1 H NMR spectra of the crude products... S10 S1

2 Experimental Section Materials Chemical reagents were purchased from Sigma-Aldrich, Acros or Alfa Aesar (France) and used as received. Metal oxide supports Al 2 O 3 ( -Al 2 O 3 nanopowder, particle size < 50 nm, SSA> 40 m²/g), TiO 2 (anatase nanopowder, primary particle size 21 nm, SSA = m²/g) and CeO 2 (nanopowder, particle size < 50 nm, SSA = 30 m²/g) were purchased from Sigma-Aldrich and used as received. Milli-Q water was used for synthesis and analysis. Instruments MW irradiation was performed in a CEM Discover System by assigning the temperature with continuous adjustment of irradiation power (Dynamic Program, maximal power: 300W, maximal pressure: 17 bar). Temperature was measured using an IR probe. Transmission electron microscopy (TEM) observation was performed using a Philips TECNAI 200F20 microscope. Images were recorded in bright-field. The samples for TEM were prepared as follow: the catalyst was suspended in EtOH, a drop was deposit on a Cu grid with a carbon support membrane and the grid was let dried 15 h. Gold particle size distribution was determined by counting 100 particles from multiple separate catalyst particles. After dissolving the catalyst into aqua regia (HCl/HNO 3 3:1), the metal content of the catalysts was determined by Atomic Absorption Spectroscopy (AAS) using a Perkin Elmer AAnalyst 300 equipped with a gold lamp ( =242.8 nm, slit = 0.7 nm) or by ICP-OES using 720-ES ICP-OES spectrometer from Agilent. The powder X-ray diffraction (XRD) experiments were performed at room temperature on a diffractometer (Bruker D8 Advance XRD) equipped with a Cu X-ray tube (40 kv, 40 ma). The step size was 0.02 degree. Conversion rate of sugars into corresponding aldonates was determined using 1 H NMR and High-Performance Liquid Chromatography. 1 H and 13 C NMR spectra were recorded on a BRUKER DMX300 spectrometer (at 300 and 75 MHz respectively) or on a BRUKER 400 MHz Advance III HD spectrometer (at 400 and 100 MHz respectively). Assignments of 1 H and 13 C signals were performed using correlated spectroscopy (COSY) and heteronuclear single quantum correlation (HSQC). Oxidized sugars were identified by comparing the 1 H NMR spectrum with that of initial sugars. Conversion rate was determined comparing the H 2 signal of aldonate to the H 1 signals ( and ) of initial sugar. The as-obtained conversion rate was compared with that determined by HPLC. HPLC analyses were performed on a Waters system equipped with an Evaporating Light Scattering Detector (ELSD) (Polymer Laboratoire), a Waters 2996 Photodiode Array Detector, a Waters 2767 Sample Manager and DEAE column (Tosoh Bioscience, TSKgel, 5PW). The elution was carried out using a gradient of ammonium formiate with a flow of 1 ml/min. S2

3 Catalysts characterization XRD analysis A) Al 2 O 3 Au/Al 2 O 3 B) Scattering angle ( 2θ, Cu Kα) TiO 2 Au/TiO Scattering angle ( 2θ, Cu Kα) S3

4 C) CeO 2 Au/CeO Scattering angle ( 2θ, Cu Kα) D) Au/Al 2 O 3 Au/Al 2 O 3 after 5 runs Scattering angle ( 2θ, Cu Kα) Figure S1: X-ray diffractograms before (red line) and after gold deposition (blue line) on Al 2 O 3 (A), TiO 2 (B), CeO 2 (C) and X-ray diffractograms of initial Au/Al 2 O 3 (red line) and of Au/Al 2 O 3 after 5 runs (blue line) S4

5 TEM analysis A) Au/Al 2 O 3 mean size: 2.4 ± 0.5 nm B) Au/CeO 2 mean size: 2.9 ± 0.7 nm Size (nm) Size (nm) C) Au/TiO 2 mean size: 2.4 ± 0.6nm D) Au/Al 2 O 3 (1.9% Au) mean size: 7.4 ± 1.4 nm Size (nm) Size(nm) Figure S2: TEM micrographs and gold particle size distribution (inset) of the synthesized catalysts. Conversion rate determination The same characterization procedure was applied for each experiment to determine the conversion rate. As example, the reaction performed using Au/Al 2 O 3 catalyst is shown here, with aerobic or microwave-assisted method. The area of H 2 peak of synthesized gluconate ( 4.14 ppm, d, J=3.7 Hz) was compared to the area of H 1 peaks of residual glucose (H 1 =5.24 ppm, d, J=3.7 Hz and H 1 =4.65 ppm, d, J=7.9 Hz,) to calculate a conversion rate (Figure S3) according to the formula : A (H2 gluconate) (A (H1 α glucose) + A (H1 β glucose) + A (H2 gluconate) S5

6 Figure S3: 1 H NMR spectra (in D 2 O) obtained for glucose (A), commercial gluconic acid (B), and microwave-assisted oxidation of glucose using 3 eq. H 2 O 2 and Au/Al 2 O 3 after 5 min (C) and 10 min (D) S6

7 The conversion rate calculated by determined by NMR can be confirmed by integration of HPLC peaks of gluconate (RT=14.6 min) and residual glucose (RT=2.6 min). Figure S4: HPLC profiles obtained for glucose (A), commercial gluconic acid (B), and oxidation of glucose after 5 min (C) and 10 min (D). Peak at 2.27 min (*) is due to the Na + salts. S7

8 Oxidation of glucose using MW-assisted procedure depending on the catalyst (A) * * (B) * * (C) * * Figure S5: 1 H NMR spectra (in D 2 O) obtained for microwave-assisted oxidation of glucose using Au/Al 2 O 3 (A), Au/CeO 2 (B) and Au/TiO 2 (C). Peak assigned by (*) corresponds to sodium glucarate; reaction conditions: 5 % glucose solution, 3 eq. H 2 O 2, 1 eq. NaOH, 10 min MW irradiation at 60 C S8

9 Gold content influence Figure S6: 1 H NMR spectrum (in D 2 O) obtained for microwave-assisted oxidation of glucose using Au/Al 2 O 3 1.9%. Peaks assigned by (*) corresponds to sodium glutarate; reaction conditions: 5 % glucose solution, 3 eq. H 2 O 2, 1 eq. NaOH, 10 min MW irradiation at 60 C. S9

10 1H NMR spectra of the crude products Figure S7: 1 H NMR spectra (in D 2 O) obtained for microwave-assisted oxidation of methylglucoside (A), glucose (B), galactose (C) and mannose (D) using Au/Al 2 O 3. Peak assigned by (*) corresponds to corresponding sodium aldarates; reaction conditions: 5 % sugar solution, 1.1 eq. H 2 O 2, 1 eq. NaOH, MW irradiation: 20 min at 60 C S10

11 (E) (F) (G) (H) Figure S8: 1 H NMR spectra (in D 2 O) obtained for microwave-assisted oxidation of glucuronic acid (E), trehalose (F), maltose (G), lactose (H), using Au/Al 2 O 3. Reaction conditions: 5 % glucose solution, 1.1 eq. H 2 O 2, 2 eq. K 2 CO 3, MW irradiation: 20 min at 60 C S11

12 Figure S9: 1 H NMR spectra (in D 2 O) obtained for microwave-assisted oxidation of cellobiose, using Au/ Al 2 O 3. Reaction conditions: 5 % glucose solution, 1.1 eq. H 2 O 2, 2 eq. K 2 CO 3, MW irradiation: 20 min at 60 C S12