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Problem statement: The studied dihydropyridone was synthesized for the first time via the microwave assisted reaction of curcumin and methylamine and it is important to support the mechanism by the crystal structure. Approach: The crystal structure of the title compound was determined using high resolution x-ray diffraction. PowderSolve program was used to solve the structure while the refinement was done in material studio Reflex module. Results: The findings obtained with high-resolution x-ray powder diffraction and molecular location methods based on simulated annealing algorithm after Rietveld refinement showed that the monoclinic unit cell was a = 13.4925 [Angstrom], b = 12.8162 [Angstrom], c = 11.5231 [Angstrom], [alpha] = 90.000[degrees], [beta] = 99.0401[degrees], [gamma] = 90.000[degrees]; cell volume = 1967.85 [[Angstrom].sup.3] and space group P 21/a with 4 molecules in a unit cell. Conclusion/Recommendations: Powder diffractometry could be a powerful tool for determining crystal structures for organic molecules. Key words: Dihydropyridone, x-ray powder diffraction, rietveld refinement, PowderSolve, treor, INTRODUCTION Dihydropyridones are important intermediates for synthesis of natural products, particularly alkaloids and many approaches to their synthesis have been developed (Donohoe et al., 2009; Comins and Ollinger, 2001; Song [...]

Problem statement: QSAR techniques increase the probability of success and reduce time and coast in drug discovery process. The study presented QSAR investigation on 32 bioactive aziridinylbenzoquinones that have activity against lymphoid leukemia. Approach: Molecular descriptors, molecular weight, total energy, hardness, chemical potential, electrophilicity index, HOMO and LUMO energies were calculated. Initial geometry optimizations were carried out with the AM1 Hamiltonian. The lowest energy conformations were subjected to single point calculations by the DFT method by employing Beck's Three-Parameter hybrid functional (B3LYP) and pvDZ basis set. Several models for the prediction of biological activity have been drawn up by using the multiple regression technique. Results: A model with hapta parametric linear equation with [R.sup.2] value of 0.886 was presented. Conclusion: The biological activity of the studied compounds can be modeled with quantum chemical molecular descriptors. Key words: Aziridinyl benzoquenones, lymphoid leukemia, QSAR, DFT, electrophilicity, INTRODUCTION Quantum chemical descriptors have been extensively used in Quantitave Structure-Activity Relationship studies in biochemistry. Numerous reviews have been published on the applications of quantum chemical descriptors (Parthasarthi et al., [...]

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1J(15N,H) coupling constants for enaminones and NH‐forms of intramolecularly hydrogen‐bonded Schiff bases as model compounds for sp2‐hybridized nitrogen atoms are evaluated using density functional theory (DFT) to find the optimal functionals and basis sets. Ammonia is used as a test molecule and its one‐bond coupling constant is compared with experiment. A methylamine Schiff base of a truncated molecule of gossypol is used for checking the performance of selected B3LYP, O3LYP, PBE, BHandH, and APFD density functionals and standard, modified, and dedicated basis sets for coupling constants. Both in vacuum and in chloroform, modeled by the simple continuum model of solvent, the modified basis sets predict significantly better the 1J(15N,H) value in ammonia and in the methylamine Schiff base of a truncated molecule of gossypol than the standard basis sets. This procure is then used on a broad set of intramolecularly hydrogen‐bonded molecules, and a good correlation between calculated and experimental one‐bond NH coupling constants is obtained. The 1J(15N,H) couplings are slightly overestimated. The calculated data show for hydrogen‐bonded NH interatomic distances that the calculated values depend on the NH bond lengths. The shorter the bond lengths, the larger the 1J(15N,H). A useful correlation between 1J(15N,H) and NH bond length is derived that enables realistic predictions of one‐bond NH coupling constants. The calculations reproduce experimentally observed trends for the studied molecules. [ABSTRACT FROM AUTHOR]

A number of 5‐acyl rhodanines and thiorhodanines with bulky acyl groups (pivaloyl and adamantoyl), not previously available, have been synthesized. The compounds are shown to exist in the enol form. Structures have been calculated using both the MP2 approach and the B3LYP‐GD3BJ functional and the 6‐311++G(d,p) basis set. Hydrogen bond energies are estimated by subtracting energies of a structure with the OH group turned 180° from those of the intramolecularly hydrogen‐bonded one. Properties such as OH chemical shifts, two‐bond isotope effects on 13C chemical shifts, electron densities at the bond critical point from atoms in molecules analysis, and the hydrogen bond energies show that the sterically hindered compounds have stronger hydrogen bonds than methyl or isopropyl derivatives. The combination of oxygen and sulfur derivatives enables a detailed analysis of hydrogen bond energies. [ABSTRACT FROM AUTHOR]