- Hydrolysis of methylacetoin ethyl phosphate. competing pathways for carbonyl hydrate participation in a model for biotin carboxylation
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Methylacetoin ethyl phosphate (1) is a phosphodiester with a carbonyl group β to phosphorus. The phosphate ester of a carbonyl hydrate, expected to be generated from an intramolecular reaction of 1 in base, is a model for an enzymic reaction intermediate which would form from the reaction of the tetrahedral addition production of biotin and bicarbonate with ATP. The hydrolysis of 1 is 104-105 times more rapid than that of dimethyl phosphate, extrapolated to common conditions (1 M NaOH, 55°C). Kinetic, product, and isotope labeling studies show that the hydrate of the carbonyl group of 1 serves as an intramolecular nucleophile toward phosphorus, forming the expected phosphate ester of the carbonyl hydrate through cyclic phosphorane intermediates. These adducts decompose by routes which parallel the proposed enzymic mechanism. In addition, solvent isotope incorporation reveals a route not found in reactions of carbonyl-substituted phosphotriesters: the conjugate base of the carbonyl hydrate acts an intramolecular nucleophile at the adjacent carbon atom, forming an unstable hydroxyoxirane (which becomes methylacetoin) and ethyl phosphate. An analogous reaction of ribonucleic acids (and RNAzymes) would have the 2′ hydroxyl group react at the 3′ carbon to form an oxyoxirane, cleaving the 3′ internucleotide bond.
- Taylor, Scott D.,Kluger, Ronald
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p. 867 - 871
(2007/10/02)
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- Anomalous Michaelis-Becker Reaction: 1-Phenylethan-1,2,2-triphosphonic Acid and their Esters
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Sodium dialkylphosphite reacts with trichlorovinylbenzene to yield in an one-batch procedure 1-phenyl-1,2,2-ethanetriphosphonic acid hexaalkyl esters.A carbanionic intermediate of an "anomalous Michaelis-Becker reaction" is deduced.Acidolysis of esters leads to the parent triphosphonic acids.NMR parameters of this acid are strongly influenced by protolytic equilibrium. - Key words: One-batch synthesis, Oligophosphonic Acid, NMR Spectra
- Fischer, Ulrich,Haegele, Gerhard
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p. 1152 - 1156
(2007/10/02)
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