- Secondary Deuterium Kinetic Isotope Effects in the Cleavage of Thiamin and N-Methylthiaminium Ion: First Evidence To Identify the Rate-Limiting Step
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Thiamin and 1'-methylthiaminum ion deuterated at the 6'- and N-methylene positions were cleaved by sulfite ion in aqueous phosphate at 25 deg C.Observed secondary kinetic isotope effects (standard deviation of the ratio) were inverse for the 6'-position, 0.95 (0.09) and 0.95 (0.03), respectively, and normal for the N-methylene group., 1.08 (0.09) and 1.10 (0.03), respectively.These results confirm the multistep mechanism first proposed by us (J.Am.Chem.Soc. 1977, 99, 3134).They prove for the first time that sulfite ion adds to the 6'-position and that fragmentation of the CH2-thiazole bond in the resultant adduct contributes to the rate in the multistep mechanism.
- Uray, Georg,Celotto, Claude,Ibovnik, Anton,Zoltewicz, John A.
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- THIAMIN YLIDE: iSOLATION AND IDENTIFICATION
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The action ot two equivalents of NaOEt on thiamin hydrochloride in EtOH gives a neutral compound.Spectroscopic data and its chemical behavior indicated that the compound is thiamin ylide 1.The chemical behaviors of 1 are entirely consistent with those of in situ generated thiamin ylide.
- Sugimoto, Hirohiko,Hirai, Kentaro
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p. 883 - 886
(2007/10/02)
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- REACTION OF N-ALKYLTHIAZOLIUM HALIDES, INCLUDING THIAMINE, WITH SUPEROXIDE ION. CHEMISTRY AND BIOLOGICAL IMPLICATIONS.
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N-alkylthiazolium halides are transformed by KO2 into the corresponding thiazolin-2-ones and thiazolin-2-thiones; the same reactions occur with thiamine, whose thiazolin-2-one pyrophosphate has been reported to be a strong inhibitor of pyruvic dehydrogenase.
- Dondoni, Alessandro,Galliani, Guido,Mastellari, Annarosa,Medici, Alessandro
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p. 2917 - 2920
(2007/10/02)
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