We have shown that site-specific natural isotope fractionation of hydrogen studied by NMR (SNIF-NMR) is an important source of information on the mechanistic and environmental effects which govern the photosynthesis of sugars and their fermentation into ethanol. Three isotope ratios associated with the methyl, methylene, and hydroxyl sites of ethanol are determined in achiral media. In this study we show that complementary information about possible stereospecific mechanisms involving the methylenic hydrogens is also rendered accessible by 2H-NMR enantiomeric resolution. The synthesis of mandelate esters enables exchange between the pro-R site of ethanol and water to be investigated. Simultaneous access to the three site-specific isotope ratios of the ethyl group is obtained at isotopic dilutions close to the natural ones. Mediation of the exchange by the enzymic system alcohol dehydrogenase-alpha-lipoyldehydrogenase and by the yeast Saccharomyces cerevisiae are compared. The progress of the reaction can be followed quantitatively as a function of time and the occurrence of glycolytic metabolism of endogeneous materials by yeast can be substantiated in a one-pot experiment.

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R e p le 13 dtcembre 1990 CLAUDE RABILLER, PHIL~PPE EYMARD et MAHMOUD MESBAHI. Can. J. Chem. 69, 1281Chem. 69, (1991.Les dtrivts phosphatts du glucose et du fructose sont des intermtdiaires importants dans la fermentation des sucres. L'ttude du devenir de leurs protons (ou deuttrons) par spectroscopie RMN doit fournir des informations sur les transferts de protons (ou deuterons) susceptibles d'intervenir au cours de cette bio-transformation. Dans cette note, nous dkcrivons I'influence de la complexation de ces mttabolites avec le chlorure de prastodyme ainsi que celle du pH sur leurs dtplacements chimiques protoniques. On dtcrit par ailleurs les conditions dans lesquelles tous les protons des formes cr et P de ces sucres cycliques sont individualists. On a trouvt que le glucose-1-phosphate prtsente les meilleures aptitudes pour ce type d'etude. De plus, la comparaison du comportement de ces composts avec celui de l'acide 2-phosphoglyctrique permet de prtciser la conformation de ce dernier.Mots cle's : dtrivCs phosphatts des sucres, RMN, effets des terres rares. CLAUDE RABILLER, PHILIPPE EYMARD, and MAHMOUD MESBAHI. Can. J. Chem. 69, 1281Chem. 69, (1991.Phosphate derivatives of glucose and fructose are well-known intermediates in sugar fermentation. Proton and deuterium NMR spectroscopy studies of the fermentation process provide information about proton (deuteron) transfers that are likely to occur in such biotransformations. In this paper we describe the influence of complexation of those metabolites with praseodymium trichloride and of pH on their proton NMR chemical shifts. We determine the conditions under which all the protons of both the cr and p forms of these cyclic sugars are separated. Glucose-1 phosphate was found to be the most suitable derivative for this type of study. Furthermore, comparing the behaviour of these compounds with 2-phosphoglyceric acid allows us to specify the exact conformation of the latter.

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