Tritiated water and tritiated substrates have been used to study exchange reactions catalyzed by Escherichia coli 2-oxo-4-hydroxyglutarate aldolase (4-hydroxy-2-oxoglutarate glyoxylate-lyase, EC 4.1.3.16, 2-oxo-4-hydroxyglutarate in equilibrium pyruvate + glyoxylate). With pyruvate, the enzyme catalyzes a rapid first-order exchange of all three methyl hydrogens in the absence of added acceptor ...

The enzyme 4-oxalocrotonate tautomerase (4-OT), which has a catalytic N-terminal proline residue (Pro1), can promiscuously catalyze various carbon-carbon bond-forming reactions, including aldol condensation of acetaldehyde with benzaldehyde to yield cinnamaldehyde, and Michael-type addition of acetaldehyde to a wide variety of nitroalkenes to yield valuable γ-nitroaldehydes. To gain insight int...

Under basic conditions 4,5,12,13-tetraacetyl[2.2]paracyclophane (9) cyclizes by a double aldol condensation to provide the two aldols 12 and 15 in a 3:7 ratio. The structures of these compounds were obtained from X-ray structural analysis, spectroscopic data, and mechanistic considerations. On acid treatment 12 is dehydrated to a mixture of the condensed five-membered [2.2]paracyclophane deriva...

The monomer 3-hexylthiophen-2,5-dicarboxaldehyde was synthetized from precursor 3-hexylthiophene by VilsmeierHaack reaction. Three p-type semiconductor polymers (PHT-P, PHT-B and PHT-H) were aldol condensation this with three different ketones (propanone, butanone hexanone). composites created adding PbS/ZnS nanoparticles to these polymers. Light absorption increased the red composites. Electri...

The identity of the active sites of hydrophobic Lewis acid zeolites was elucidated by solid-state P nuclear magnetic resonance (NMR) spectroscopy following adsorption of trimethylphosphine oxide (TMPO) probe molecules. The adsorption of TMPO on these materials resulted in distinct P NMR resonances between δiso = 59.9 and 54.9 ppm that correspond to unique chemical environments of the Lewis acid...