Stereochemistry of benzophenone derivatives: crystal and molecular structure of 3,3'-dibromobenzophenone

The structure of 3,3'-dibromobenzophenone has been reinvestigated using new three-dimensional data. Crystals of 3,3'-dibromobenzophenone are orthorhombic: a=4.05, b=11·74, c=24.80 Å , Z=4, space group Pbcn. The structure has been refined by three-dimensional methods, including anisotropic full-matrix least squares, to an R index 0.104. The conformation of isolated molecules of benzophenone, pp'-dimethoxy benzophenone and 3,3'-dibromobenzophenone have been calculated by semi-empirical methods, and the results are compared with those obtained from X-ray crystallographic investigations on these compounds. It has been found that the calculated geometries of isolated molecules of benzophenone and its derivatives are different from those observed in the crystal structures of these compounds

Crystal and molecular structure of pyroglutamic acid (5-oxoproline)

The crystal structure of the title compound has been determined by the symbolic addition method from 934 observed three-dimensional photographic data. Crystals are monoclinic with a=8.14, b=8.86, c=9.32 Å (all ± 0.02 Å), and β=116.5°(2), Z=4, space group P21/c. The structure was refined by full-matrix least-squares method to R 0.091. The structure is stabilised by N-H … O and O-H…O type hydrogen bonds. The dimensions of the amide group, which is significantly non-planar, are compared with those found in other peptides

Solvent interactions with β-Cyclodextrin as observed in crystal structures

Nimesulide, an anti-inflammatory drug, was complexed with β cyclodextrin (βCD) in the presence of lysine in 10:10:1 molar ratio to increase its water solubility. The complexation did not take place in the crystal structure, but it exhibits two different crystal forms. The crystal structures show a difference in hydration pattern and conservation of the organic molecule 2,4 methyl pentane diol (MPD) binding site. Molecular mechanics studies carried out suggest a probable mode of binding of nimesulide with βCD

Crystal and molecular structure of glycyl-L-ieucine

The crystal structure of the title compound has been determined by direct methods from diffractometer data. Crystals are monoclinic, with Z=2 in a unit cell of dimensions: a=6.369(5), b=5.565(5), c=15.350(10)Å ,β=102.77(4)°, space group P21. The structure was refined by least-squares to R 0.044 for 823 observed reflections. The four protons available for hydrogen-bond formation are a three-dimensional network which stabilizes the structure. There is significant non-planarity of the peptide linkage, the torsion angle about the peptide bond being -11.4°. The nitrogen atom of the peptide group is significantly pyramidal. The molecular conformation is discussed

Structural basis for selective inhibition of COX-2 by nimesulide

Nimesulide 1 is a novel nonsteroidal antiinflammatory drug which inhibits the enzyme cyclooxygenase 2 (COX-2) more selectively than cyclooxygenase 1 (COX-1). Molecular modelling studies have been carried out on complexes of 1 with COX-1 and with mutants of COX-1 simulating COX-2. These indicate that the mutations I523V and S516A largely contribute to the selectivity. A comparative study with SC-558 2 has also been performed

First and unexpected synthesis of macrocyclic cyclophane-based unusual α-amino acid derivatives by phosphazene base without high dilution conditions

First synthesis of a macrocylic cyclophane-based unusual α-amino acid derivative 11 by coupling of ethyl isocyanoacetate with 1,2-bis(4-bromomethylphenyl)ethane under phase-transfer catalysis (PTC) conditions. Phosphazene base such as 2-tert-butylimino-2-diethylamino-1,3-dimethylperhydro-1,3,2-diazaphosphorine (BEMP) is useful to improve the yield of cyclophane derivative without high dilution conditions.© Elsevie

Synthesis of two new hexaquinanes: advanced C20 precursors to dodecahedrane

A simple synthesis of hexaquinane diones 2 and 22 involving bench-top chemicals is reported. These two hexaquinanes are advanced C20 precursors to dodecahedrane 1 either by C-C bond formation reactions or by the isomerisation approach.© Elsevie

Optimization of interactions in crystal packing revealed by crystal structures [ethyl 2-(formylamino)-3-thien-2-yl-2-(thien-2-ylmethyl)propanoate and ethyl 3-(5-bromothien-2-yl)-2-[(5-bromothien-2-yl)methyl]-2-(formylamino)propanoate]

The title compounds, C15H14NO3S2 (I) and C15H15Br2NO3S2 (II), are derivatives of Aib (α-aminoisobutyric acid) with thiophene rings substituted at the Cα position. The Cα substitution causes the backbone to assume an extended conformation in the crystal structure. N–H and C–H donors share the thiophene ring π system for X–H...π interactions. The packings of the molecules are stabilized by intermolecular N–H...O, C–H...O, C–H...π and C–H...Br hydrogen bonds. Br...O interactions and a weak dihydrogen bond have also been observed in the crystal structure of II. The packing adopted by II has maximized the number of interactions that are possible.© Elsevie