A chiral dinuclear zinc complex can effectively catalyse the direct aldol reactions of pyruvic acid ester with various chiral sugar aldehydes, thus functionally mimicking the pyruvate‐dependent type II aldolases. Application of sterically hindered aryl esters allows for the elusive aldol reaction of the pyruvate donor with controlled anti‐selectivity en route to the short and efficient synthesis of 3‐deoxy‐2‐ulosonic acids. Pyruvic acid ester is here used as a chemical equivalent of phosphoenol pyruvate (PEP) in imitation of the synthetic principle used in nature. The presented biomimetic methodologies use enol formation for the highly efficient and flexible formation of various C6–C9 ulosonic acids. Particularly, efficient and concise syntheses of 3‐deoxy‐D ‐erythro‐hex‐2‐ulosonic acid (KDG, overall 50% yield), 3‐deoxy‐D ‐ribo‐hept‐2‐ulosonic acid (DRH, overall 53% yield) and 3‐deoxy‐D ‐glycero‐D ‐talo‐non‐2‐ulosonic acid (4‐epi‐KDN, overall 78% yield) are described. This direct efficient application of pyruvic esters does not require additional demasking steps and thus surpassess previously methodologies utilising masked pyruvic synthons such 2‐acetylthiazole and pyruvic aldehyde dimethyl acetal.
The mono- and bi-polar electrodialysis processes for pyruvate recovery and pyruvic acid generation, respectively, were examined in order to determine their feasibility for application in the pyruvate production process. Under optimum process conditions (constant current mode i = 39.7 A m−2, pyruvate model solution cp = 50 g dm−3 in the monopolar electrodialysis experiment pyruvate flux reached 367 g m−2 h−1 and specific energy consumption was 1.4 kWh kg−1. In the bi-polar electrodialysis experiment under optimum process conditions (constant current mode i = 9.6 A m−2, pyruvate model solution cp = 48 g dm−3, pyruvate flux reached 125 g m−2 h−1 and specific energy consumption was 1.5 kWh kg-1. Generally speaking, performances of the bi-polar electrodialysis were equal to the best process conditions observed with mono-polar electrodialysis. On the other hand, current densities investigated in the bi-polar electrodialysis experiments were four-fold lower than those applied in the mono-polar electrodialysis experiments. Additionally, a mathematical model to represent the ion and water transport behavior of an electrodialysis process for concentrating pyruvic acid under the influence of different current density was developed. Estimation of both the model parameters and model validation were demonstrated in the work. 相似文献
This study reports the electrohydrodimerization of pyruvic acid to 2,3-dimethyltartaric acid in sulphuric acid medium (0.5 M H2SO4) on a lead cathode. The main products detected were lactic acid and 2,3-dimethyltartaric acid. The selectivity towards the formation of 2,3-dimethyltartaric acid was studied vs. pyruvic acid concentration in sulphuric acid solution, at −1.1 V vs. MSE. The best selectivity of 2,3-dimethyltartaric acid reached 69% for an initial concentration of 1.7 M pyruvic acid. The yield of pyruvic acid was 84%. 相似文献
Heart mitochondrial oxidation of palmityl CoA and pyruvic acid was studied in rats and in the monkeyMacaca fascicularis to determine the effects of feeding partially hydrogenated herring oil. Herring oil glycerides contain cetoleic acid (cis-11-docosenoic) which could have a similar effect to erucic acid (cis-13-docosenoic) in causing a rat cardiomyopathy. The initial rat heart mitochondrial response to dietary cetoleic acid (67%cis, 33%trans) was an in vitro decrease in palmityl CoA oxidation. Prolonged feeding of cetoleic acid mixture was associated with a significant
metabolic adaptation, increasing pyruvate and palmityl CoA oxidation above control levels. In vitro addition of cetoleyl CoA
(purecis isomer) stimulated pyruvate dehydrogenase activity, a possible response to decreased β-oxidation. There was no significant
adaptive change in pyruvate or palmityl CoA use in monkeys after prolonged feeding of partially hydrogenated herring oil.
Cetoleyl CoA was a good substrate for monkey heart carnitine acyl transferase even in the presence of palmityl CoA. These
observations suggest that C22 fatty acids may be matabolized more rapidly in monkey heart than in rat heart. Metabolic differences argue against using
the rat as an experimental model for studying possible cardiotoxic effects of docosenoic acids in primates. 相似文献