Abstract The keto‐switched photocatalysis of covalent organic frameworks (COFs) for efficient H 2 evolution was reported the first time by engineering, at a molecular level, local structure and component skeletal building blocks. A series imine‐linked BT‐COFs were synthesized Schiff‐base reaction 1, 3, 5‐benzenetrialdehyde with diamines to demonstrate structural reconstruction enol keto configu...

The glyceraldehyde conversion in terms of dehydration, keto-enol tautomerism, and retro-aldol reaction has been discussed by means of ab initio density functional theory calculation to elucidate the catalytic water molecule influence on the pathways. The optimized structures of reactants, products, and transition state structure on the glyceraldehyde conversion pathways were fully optimized wit...

An isopyrazole (4H-pyrazole)-embedded nonane-2,4,6,8-tetraone derivative was synthesized as a masked-tetraketone for stepwise and multiple functionalization. The has six possible tautomers, but exists predominantly 12π-electron conjugated keto-enamine-imine-enol form, which also observed in the solid state by single crystal X-ray analysis. Stepwise functionalization to introduce metal-coordinat...

New DKR type: An N-heterocyclic carbene (NHC)-catalyzed dynamic kinetic resolution of racemic α-substituted β-keto esters has been developed. This method relies on the epimerization of an NHC-enol intermediate before subsequent aldol/acylation events. Highly substituted β-lactones are produced in good yield with good to excellent selectivities (see scheme).

We have investigated deuterium-substitution and solvent effects for the keto-enol tautomerization of acetylacetone (Hacac) confined in 10 – 100 nm scale spaces (called extended-nano spaces) based on NMR spectroscopic results, and elucidated the tautomeric reaction mechanisms in the extended-nano spaces.

Studies with deuterium as a tracer have shown that wheat germ and pig heart malic dehydrogenase act on the keto form of oxaloacetic acid (1, 2). The keto form of this acid has also been shown to arise in the enzymatic carboxylation of phosphorylenolpyruvate by wheat germ phosphoryl-enolpyruvate carboxylase (3) and by avian liver phosphoryl-enolpyruvate carboxylase kinase (2). In an attempt to e...

The structural changes taking place in the enzyme thymidine phosphorylase (TPase, also known as PD-ECGF) that are required to achieve catalytic competence upon binding thymidine and phosphate have been simulated by means of targeted molecular dynamics (tMD). The hinge regions were characterized by structural homology comparisons with pyrimidine nucleoside phosphorylase, whose X-ray structure ha...

A GC/MS method suitable to conduct practical toxicological analyses of unspecified opiates including hydrocodone or hydromorphone is presented. Silylation can be a convenient reaction to derivatize unknown analytes in toxicological samples. However, silylation of drugs with tautomeric keto/enol groups in molecular structure can cause analytical problems due to poor reproducibility. After using ...

2-Keto-3-methylvaleric acid (KMVA) has been found not to undergo spontaneous keto-enol tautomerization in neutral aqueous solution, alone or in the presence of large concentrations of pyridoxamine or pyridoxamine-5-phosphate. This finding denies the commonly held suppositions that 3R-KMVA is derived spontaneously from 3S-KMVA in vivo, and that L-alloisoleucine is the product of the reamination ...

The low-lying excited singlet states of the keto, enol, and keto-imine tautomers of cytosine have been investigated employing a combined density functional/multireference configuration interaction (DFT/MRCI) method. Unconstrained geometry optimizations have yielded out-of-plain distorted structures of the pi --> pi and n --> pi excited states of all cytosine forms. For the keto tautomer, the DF...