ABSTRACT
Glutamic acid, an abundant nonessential amino acid, was converted into 2-pyrrolidone in the presence of a supported Ru catalyst under a pressurized hydrogen atmosphere. This reaction pathway proceeded through the dehydration of glutamic acid into pyroglutamic acid, subsequent hydrogenation, and the dehydrogenation-decarbonylation of pyroglutaminol into 2-pyrrolidone. In the conversion of pyroglutaminol, Ru/Al2 O3 exhibited notably higher activity than supported Pt, Pd, and Rh catalysts. IR analysis revealed that Ru can hydrogenate the formed CO through dehydrogenation-decarbonylation of hydroxymethyl groups in pyroglutaminol and can also easily desorb CH4 from the active sites on Ru. Furthermore, Ru/Al2 O3 showed the highest catalytic activity among the tested catalysts in the conversion of pyroglutamic acid. Consequently, the conversion of glutamic acid produced a high yield of 2-pyrrolidone by using the supported Ru catalyst. This is the first report of this one-pot reaction under mild reaction conditions (433â K, 2â MPa H2 )" which avoids the degradation of unstable amino acids above 473â K.
ABSTRACT
A microfluidic device was developed for rapid determination of the minimum inhibitory concentration (MIC) of antibiotics against bacteria. A small volume of sample solution was introduced into multiple chambers simultaneously, and the growth of bacteria was quantified using a noninvasive three-dimensional (3D) visualization technique.
Subject(s)
Anti-Bacterial Agents/pharmacology , Escherichia coli/drug effects , Microfluidic Analytical Techniques/methods , Anti-Bacterial Agents/chemistry , Escherichia coli/physiology , Microbial Sensitivity Tests/instrumentation , Microbial Sensitivity Tests/methods , Microfluidic Analytical Techniques/instrumentation , Time FactorsSubject(s)
Entropy , Guanidine/chemistry , Phenols/chemistry , Thiourea/chemistry , Catalysis , Models, Biological , Molecular ConformationABSTRACT
Catalytic enantio- and diastereoselective nitroaldol reactions were explored by using designed guanidine-thiourea bifunctional organocatalysts under mild and operationally simple biphasic conditions. These catalytic asymmetric reactions have a broad substrate generality with respect to the variety of aldehydes and nitroalkanes. Based on this catalytic nitroaldol process, straightforward syntheses of cytoxazone and 4-epi-cytoxazone were achieved. These catalytic nitroaldol reactions require KI as an additive for highly asymmetric induction; it operates by inhibiting the retro mode of the reaction. On the basis of studies of structure and catalytic-activity relationships, a plausible guanidine-thiourea cooperative mechanism and a transition state of the catalytic reactions are proposed. Drastic substituent effects on the catalytic properties of this catalyst may lead to the development of new chiral surfactants.
