In the present work, DFT calculations are employed to obtain the optimized structures of 4- acyl pyrazolone tautomers (19 tautomers) using B3LYP/6-311++G** calculations. In addition, molecular parameters, IR frequencies and relative energies are extracted for all tautomers. The existence of aromatic ring, keto tautomer (versus enol tautomer), N-H bond (versus C-H bond) and C=N double bond (vers...

Lithium complexes were prepared with phenylphosphinic and phenylphosphonic 15 acids. The complexes were studied in the solid state using Fourier transform infrared spec16 troscopy spectroscopy and in solution (methanol) using 1H, 13C, and 31P Nuclear magnetic 17 resonance spectroscopy (NMR) spectroscopy; the most preferred structures of the complexes 18 were determined by density functional the...

8-Hydroxy-2-[2-(3-hydroxy-4-methoxyphenyl)ethenyl]-7-quinoline carboxylic acid and 8-hydroxy-2-[2-(3-methoxy-4-hydroxyphenyl)ethenyl]-7-quinoline carboxylic acid inhibit the processing and strand transfer reactions catalyzed by HIV-1 integrase with an IC50 of 2 microM. Some of their spectral properties are briefly reported. Their fluorescence is so weak that it is of no use in an experimental d...

The histidine imidazole side chain plays a critical role in protein function and stability. Its importance for catalysis is underscored by the fact that histidines are localized to active sites in ∼ 50% of all enzymes. NMR spectroscopy has become an important tool for studies of histidine side chains through the measurement of site-specific pK(a)s and tautomer populations. To date, such studies...

Structural diversification of canonical nucleic acid bases and nucleotide analogues by tautomerism has been proposed to be a powerful on/off switching mechanism allowing regulation of many biological processes mediated by RNA enzymes and aptamers. Despite the suspected biological importance of tautomerism, attempts to observe minor tautomeric forms in nucleic acid or hybrid nucleic acid-ligand ...

The title mol-ecule, C(15)H(21)N(3)S, exists as the thione tautomer in the solid state. The 1,2,4-triazole ring is almost planar (r.m.s. deviation = 0.004 Å) and the prop-2-en-1-yl chain is close to being perpendicular to this plane [C-N-C-C torsion angle = 77.1 (5)°]. In the crystal, centrosymmetric dimeric aggregates are formed by pairs of N-H⋯S hydrogen bonds as parts of eight-membered (⋯HNC...