D isotopomer quantification
For NMR measurements of intramolecular D abundances, each sample of the glucose derivative, prepared as described above, was dissolved in a mixture of 83% v/v acetonitrile, 17% C6F6 and 0.01% C6D6 then transferred to a 5-mm NMR tube with a PTFE valve (J. Young Scientific Glassware Ltd., Windsor, U.K.) containing ~5 mg of NaHCO3. D-NMR measurements were acquired and processed as described by Betson et al . (2006) using an AVANCE III 850 spectrometer (Bruker BioSpin GmbH, Rheinstetten, Germany) equipped with a 19F lock and a cryogenic probe optimized for D detection. D-NMR spectra were integrated by deconvolution with a Lorentzian line shape fit, using TopSpinTM 3.2 (Bruker BioSpin GmbH, Rheinstetten, Germany). The D6S /D6R isotopomer ratio was determined as the ratio of the integrals of the D6S and D6R signals (Fig. 1). For each sample, five to eight spectra were recorded and the average of the D6S /D6Rratios was calculated.