O. M. Peeters

The interaction of chromium(VI), chromium(III) and chromium(II) with diphenylcarbazide, diphenylcarbazone and diphenylcarbadiazone

Abstract Qualitative tests on the reaction between chromium in its different oxidation states and pure diphenylcarbazide (DPCI), diphenylcarbazone (DPCO), and diphenylcarbadiazone are described. It is shown that the magenta-coloured complex results from the reaction of chromium(III) with diphenylcarbazone. From quantitative measurements, the stoichiometry, the molar absorptivity and the conditional stability constant of the complex were determined. The stoichiometry of the preceding redox reactions, when chromium(VI) interacts with DPCI and chromium(II) with DPCO, was also established. The results confirmed the qualitative findings.

X-Ray and theoretical structural study of novel 5,6,7,8-tetrahydrobenzo-4H-pyrans

Abstract The X-ray crystal structure of three substituted tetrahydrobenzo-4H-pyrans ( 6a–c ) is presented and the experimental findings compared with the theoretical values calculated at the semiempirical (AM1, PM3) and ab initio (HF/6-31G∗) levels. A good agreement between both experimental and theoretical data is found showing a flattened boat conformation for the 4H-pyran ring and a pseudo-axial orientation of the aryl ring on the C4 position. The geometrical features of these systems ( 6a–c ) reveal that they present the structural requirements to act as calcium antagonists.

Pyridazine Derivatives. Part 21: Synthesis and Structural Study of Novel 4-Aryl-2,5-dioxo-8-phenylpyrido[2,3-d]pyridazines

Abstract New substituted 4-aryl-2,5-dioxo-8-phenylpyrido[2,3-d]pyridazines 4a–f have been prepared in one step from the corresponding arylidene substituted Meldrums acid (1) and 5-amino-6-phenyl-3(2H)-pyridazinone (2) in good yields. Semiempirical theoretical calculations (AM1) reveal two favoured conformations (A and B) for compounds 4a–f, with a screw boat conformation in the pyridone system and a planar pyridazinone ring. X-Ray crystallographic analysis shows that in the solid state, conformation A bearing the phenyl ring in a pseudoaxial position is the most stable. Compounds 4a–f fulfil, from the structural point of view, all the requirements needed for exhibiting cardiotonic effects.

Synthesis of homo-N-nucleosides, a series of C1' branched-chain nucleosides

Abstract Homo-N-desoxynucleosides were synthesized starting from 2-deoxy- d -ribose using a one step epoxidation-ring closure appraoch. The configuration of the nucleosides were proven using NMR and X-ray analysis.

cis-2-sec-Butyl-4-{4-[4-(4-{[2-(2,4-dichlorophenyl)-2-(1H-1,2,4-triazol-1-ylmethyl)-1,3-dioxolan-4-yl]methoxy}phenyl)-1-piperazinyl]phenyl}-2,4-dihydro-3H-1,2,4-triazol-3-one (Itraconazole)

The molecular structure of itraconazole, C 35 H 38 C1 2 N 8 O 4 , has been determined from single-crystal X-ray diffraction data. The two molecules in the asymmetric unit differ mainly in the conformation of the methoxy-phenylpiperazine moiety. Apart from a 180° rotation of the triazole ring, the geometry of the dichlorophenylethoxytriazole moiety is almost the same as the dichlorophenylethoxyimidazole geometry found in miconazole, econazole and ketaconazole.

Crystal and molecular structure ofN-[1-(2-phenylethyl)-4-piperidinylium]-N-phenylpropanamide (fentanyl) citrate-toluene solvate

The crystal structure of fentanyl has been determined as part of a structure-activity relationship study on a congeneric series of 4-anilinopiperidines. The compound crystallizes as a citrate toluene solvate, C22H28N2O · C6H8O7 · C7H8, in the monoclinic space groupP21/c witha = 18.292(6),b = 9.825(4),c = 19.479(4) Å, β = 107.43(3) °, andZ = 4. The structure was solved by direct methods using the program Simpel, and refined by block-diagonal least squares to anR value of 0.092. The torsion angle that describes the conformation of theN-phenyl ring relative to the piperidine ring is 123 ° and differs from that found in other 4-substituted anilinopiperidines (172–177 °).

Structure of 3-{2-[4-(6-fluoro-1,2-benzisoxazol-3-yl)piperidino]ethyl}-6,7,8,9-tetrahydro-2-methyl-4H-pyrido[1,2-a]pyrimidin-4-one (risperidone)

The benzisoxazole and pyrimidine moieties are essentially planar and the dihedral angle between these planes is 5.6 (1) o . The piperidine ring is in a slightly distorted chair conformation, while the tetrahydropyridine moiety shows a half-chair conformation. The crystal stucture is stabilized by a hydrogen bond between the H atom on position 4 of the benzisoxazole and the O atom of the pyrimidinone of a translated (x, y-1, z) molecule [C...O=3.372 (7), H...0=2.327 A, C-H...O=161.6 o ]

A new synthetic method for proline diphenyl phosphonates

Abstract The diphenyl ester of the phosphonic acid analogue of proline and related dipeptides were prepared by a reaction of the corresponding N-substituted 4-aminobutyraldehyde and triphenyl phosphite. Diastereoisomers were separated and their configuration determined by X-ray crystallography.

Structure of 4(5)-nitroimidazole at 100 K

4(5)-Nitroimidazole, C 3 H 3 N 3 O 2 , M r =113.08, monoclinic, P2 1 /n, a=6.9559 (4), b=9.9130 (6), c=7.3045 (4) A, β=119.41 (4) o , V=438.8 (4) A 3 , Z=4, D m (293 K)=1.64, D x =1.7117 Mg m -3 , λ(Mo Kα)=0.71069 A, μ=0.1367 mm -1 , F(000)=232, T=100 K. Final R=0.024 for 633 unique observed [F≥4σ(F)] reflections. The molecules are planar and are stacked in planes almost parallel to the bc plane. These molecular layers are built up by three hydrogen bonds. 4-5-tautomerism is discussed

A joint theoretical and experimental structural study of 5-carboxyethyl-3-(2 '-furfurylmethyl) tetrahydro-2H-1,3,5-thiadiazine-2-thione

Abstract X-Ray analysis and semiempirical AM1 and ab initio HF/3-21G ∗ and HF/6-31G ∗ calculations reveal a favourable envelop conformation (A) for 3,5-disubstituted tetrahydro-2 H -1,3,5-thiadiazines in which the N5 atom lies out of the main plane. NOE experiments show that this conformer (A) is also found in solution.