Lars Kr. Hansen

The Polymorphism of Glycine. Thermochemical and structural aspects

X-ray, DSC and solution calorimetric investigations were carried out for α-, β- and γ-modifications of glycine. Particular attention was paid to kinetic and thermochemical aspects of γ- → α-phase transition. The temperature of this phase transition turned out to be sensitive to a) conditions under which the crystals of the γ-modification were grown, b) tempering of crystals c) form (geometry) of crystals. Kinetics of this phase transition of single crystals of γ-phase in rhomboedric form can be described by the equation for two-dimension nuclei growth, whereas for crystals of triangle geometry the equation for three dimension growth is valid. On the basis of energy parameters describing growth of α-form in γ- →α-phase transition, the kind of structure defects, which are responsible for this phase transition, was estimated. Taking into account the ΔsolHm, the absolute values of the lattice energies of the investigated polymorphs indescending order are follows: γ->α->β-modification. The obtained results are discussed with respect to the peculiarity of the crystal lattice structures, particularly the network of hydrogen bonds. The β-modification of glycine is monotropically related to the other forms, whereas γ-and α-polymorphs are enantiotropically-related phases.

Novel heteropentalenes. Synthesis of heteropentalenes from tetrahydroimidazo [1.2-d]-(1,2,4)-thiadiazoles and conversion of certain heteropentalenes to benzothiazole derivatives

Abstract Oxidation of 1 - phenylcarbamoylidazolidine - 2 - thione gives 2,3,5,6 - tetrahydro - 2 - phenylimidazo [1,2-d]- (1,2,4) - thiadiazole - 3 - one which undergoes addition reactions with heterocumulenes leading to various heteropentalenes. Oxidation of 1 - phenylthiocarbamoylimidazlidine- 2 - thione yields 1- (benzothiazol - 2- yl) - imidazolidine - 2 - thione, also obtained by acid catalysed decomposition of 3,4 - ethano - 2,3,4,5 - tetrahydro - 2, 5 - bisphenylimino - 1,6,6aS IV - trithia - 3,4 - diazapentalene. A similar acid catalysed decomposition to a benzothiazole occurs with 2,3,4,5 - tetrahydro - 1,6 - diphenyl - 3,4 - propano - 6aS IV - thia - 1,3,4,6 - tetraazapentalene -2, 5- dithione.

Crystallization and preliminary X-ray crystallographic studies of benzamidine-inhibited trypsin from the north atlantic salmon (Salmo salar)

Crystals of benzamidine-inhibited trypsin from the North Atlantic salmon (Salmo salar) have been grown from ammonium sulphate solution at pH 5.0. Two crystal forms suitable for X-ray structure analysis, obtained from a hanging-drop experiment, have been characterized. Both belong to space-group P22(1)2(1) with cell dimensions a = 39.2 A, b = 62.4 A, c = 84.6 A and a = 31.4 A, b = 74.8 A, c = 83.5 A, for forms I and II, respectively. Intensity data to 1.82 A have been collected for crystal form I on a CAD4 diffractometer, and initial phases have been obtained by molecular replacement methods. The conventional R-factor after two rounds of model building and subsequent refinement is 0.25 for data between 6.0 and 2.0 A. So far no water molecules have been included in the model.

Redetermination of p-ethoxyacetanilide (phenacetin)

The crystal structure of the title compound, C10H13NO2, has been redetermined in order to obtain more precise structure parameters.

N-(3-Hydroxyphenyl)acetamide

Acetanilide derivatives show antipyretic and analgesic actions with undesirable side effects on the human body. The crystal structures of acetanilide, (I) (Johnson et al., 1995), paracetamol (4-acetamidophenol), monoclinic form, (II) (Haisa et al., 1976), paracetamol, orthorhombic form, (III) (Haisa et al., 1974), and phenacetin (4-ethoxyacetanilide), (IV) (Patel et al., 1983), have been reported, but the structure of the title compound, (V), remained unsolved: we report it here (Fig. 1). Its geometrical parameters are normal.

The methanol hemisolvate of amiloride hydrochloride

In the asymmetric unit of N-(3,5-diamino-6-chloropyrazin-2-ylcarbonyl)-N-(diaminomethylene)ammonium chloride methanol hemisolvate, C(6)H(9)ClN(7)O(+).Cl(-).0.5CH(4)O, there are two crystallographically different amiloride molecules. Crystallographically identical amiloride molecules are stacked one above the other, alternately rotated by 180 degrees. These stacks are arranged parallel to each other, forming layer A. The least-squares plane of the non-H atoms of the other molecules lying in layer B is tilted against the corresponding plane of the molecules in layer A by an angle of 79.89 (3) degrees. The methanol molecules and Cl(-) anions are located between these layers, although the methanol molecules are closer to layer A.

Penta­carbonyl­[ethoxy(2-ethoxy-4,5-di­phenyl-1,3-cyclo­penta­dienyl)­carbene]­chromium(0)

The title compound, [Cr(C22H23O2)(CO)5], is shown to have a slightly distorted octahedral geometry around the Cr atom and a Cr=C carbene bond length of 2.111 (5) A, clearly showing double-bond character. The axial Cr—CCO bond trans to the Cr=C carbene bond is significantly shorter than the equatorial Cr—CCO bonds.

Redetermination of 3-hydroxybenzamide

The crystal structure of the title compound, C7H7NO2, has been redetermined [Katsube, Y. (1966). Bull. Chem. Soc. Jpn, 39, 2576–2588] to higher precision and with the hydrogen-bonding scheme established.

Crystal and molecular structure of D-threo-hexo-2,5-diulose; dimeric form in the solid state

In the crystalline state D-threo-hexo-2,5-diulose forms a dimer between a furanose form and a pyranose form of the sugar.

7-Azathieno[2,3-c]cinnoline

The present work represents a continuation of the investigation of the chemistry of nitropyridine derivatives, based on the methodology for nitration of pyridines developed by Professor Jan M. Bakke and co-workers at NTNU. Nitropyridines have been utilized as substrates for the formation of novel bis- and tris-heterocyclic compounds, and new synthetic routes to fused heterocycles have been developed. Several new β-carboline analogues and fused azacinnolines have been prepared based on a Suzuki coupling and subsequent cyclization approuch. The formation of 4-isocyanobut-2-enenitrile and 3-cyanopyrrole products by ring opening and ring contraction of 3-pyridyl nitrenes, respectively, is reported. 7-Azacinnolin-4(1H)-one has been prepared and tautomery investigated by NMR. The general ability of appropriate pyridyl compunds to undergo Friedlander condensation to give different 1,7-naphthyridines has been demonstrated. Bis-heterocyclic products have been prepared from methyl/allylpyridylketones fromed by Weinreb tranformations, and a method has been developed to allow for the preperation of reactive pure pyridylvinylketones to be used in further reactions, such as Diels-Alder cycloaddition reactions.