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An improved method is reported for the synthesis of 2-oxo acids and is applied to the synthesis of 2-oxo-4-phenyl-3-butynoic acid. The compound is synthesized by reacting the N-methoxy-N-methylamide of monoethyloxalic acid with lithium phenylacetylide yielding ethyl 2-oxo-4-phenyl3-butynoate (78% yield), followed by strictly pH-controlled hydrolysis to the free acid in nearly quantitative yield. The compound in shown to be a potent irreversible inhibitor of brewers'yeast pyruvate decarboxylase, in addition to producing both cis- and trans-cinnamic acids as products of turnover. The formation of these isomeric cinnamic acids can be rationalized if the thiamin diphosphate-bound α-carbanion/enamine intermediate resulting from decarboxylation is protonated at the side chain γ carbon to form two diastereomeric allenols, whose tautomerization and hydrolysis lead to the two products

On fait reagir le dicyclohexyl carbodiimide sur le O-phosphono-5 ribofuranosyle diphosphate pour obtenir le O-phosphono-5 ribofuranosyle phosphate-1,2. Une hydrolyse basique fournit les di-O-phosphono-2,5 ribofuranose et O-phosphono-5 ribofuranosyle phosphate

Carbon-13 kinetic isotope effects were determined for the decarboxylation of pyruvate by thiamin and for the decarboxylation of 2-(1-carboxy-1-hydroxyethyl)-3,4-dimethylthiazolium chloride (a covalent pyruvate-thiamin adduct) in water and in aqueous ethanol. The kinetic isotope effect for the decarboxylation step in the second system increased from 1.051 in H/sub 2/O to approximately 1.058 in 50% v/v ethanol. The isotope effect in the thiamin catalyzed model reaction increased from the 0.992 inverse effect observed in H/sub 2/O to 1.007 in 50% aqueous ethanol. The rate of decomposition of the covalent thiamin-pyruvate adduct to reactants relative to its rate of decarboxylation is greater in ethanol than in water. Further, the results suggest that the changes of the vibrational force constants in going from the ground state to the transition state are greater in aqueous ethanol than in water.