- Processes for preparing carbapenem derivatives
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The invention relates to carbapenem derivatives useful as antimicrobial agents, more particularly to intermediate compounds for the preparations thereof of the formula STR1
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- Acid-Catalyzed Hydrolysis of Ketene Dithioacetals and Trithioorthocarboxylates. Effect of β-Methyl Substitution
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Hydrolysis rates of β-methyl-substituted ketene dithioacetals were measured. β-Monomethyl and β,β-dimethyl substitutions reduced the reactivity of the parent acetal by factors of 26 and 6.7 x 105, respectively.Similar methyl substitutions of trithioorthoacetate, however, enhanced the hydrolysis reactivity by 3 and 23 times.The reversibility of protonation of ketene dithioacetal during hydrolysis was slightly increased by a β-methyl group, but dimethyl substitution seemed to inhibit reversibility by raising the potential barrier to protonation.
- Okuyama, Tadashi,Kawao, Shoji,Fueno, Takayuki
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- Substituen Effect of Chelated Cobalt. 5. Acidities of (Carboxymethyl)- and (1-Carboxyethyl)cobaloximes. A Quantitative Analysis of the β Effect
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pKa's of the weakly acidic (carboxymethyl)(ligand)cobaloximes and (1-carboxyethyl)(ligand)cobaloximes with 16 different axial ligands have been determined and correlated with those of 11 substituted acetic acids or 9 1-substituted propionic acids, respectively.Comparison of apparent ?1 values thus calculated with those previously determined by correlation of (carboxyethyl)(ligand)cobaloxime pKa's with the pKa's of 2-substituted propionic acid indicates that the (1-carboxyalkyl)cobalt comlexes show a substantial β effect as an apparent extreme donation density to the carboxyl carbon.The β effect in these complexes has been quantitated by use of a dual substituent parameter equation, the results of which show that the effect is only some 8-10percent enhanced in (1-carboxyethyl)cobaloximes relative to (carboxymethyl)cobaloximes.This result is consistent with the β effect being mediated by ?-? hyperconjugation rather than neighboring group participation.Structural effects on the extent of ?-? conjugation and the effects of ?-? conjugation on reactivity of the cobalt atom in these complexes are discussed.
- Brown, Kenneth L.,Zahonyi-Budo, Eva
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p. 4117 - 4124
(2007/10/02)
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- ACTION DE L'OZONE SUR DES DERIVES VINYLIQUES; REACTIONS CONSERVANT L'ENCHAINEMENT CARBONE.
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Ozone reacts with vinyl derivatives (sulphides, enamines, ethers) and gives abnormal reactions or/and double bond cleavages.
- Strobel, Marie-Paule,Morin, Luc,Paquer, Daniel
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p. 523 - 524
(2007/10/02)
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