Carboxylates crystal structure

The NMR spectrum of this compound shows a diamagnetic ring current of the type expected in an aromatic system. X-ray crystal structures of 1 and its carboxylic acid derivative 2 are shown in Fig. 9.2. Both reveal a pattern of bond lengths very similar to that in naphthalene (see p. 534). ... 

Fig. 9.4. (A) X-ray crystal structure of j> n-tricyclo[8.4.1.F ]hexadeca-2,4,6,8,10,12,14-heptaene. iB) X-ray crystal structure of anti stereoisomer of tricyclo[8.4.1.1 ]hexadeca-2,4,6,8,10,12,14-heptaene-5-carboxylic acid. (Reproduced from Ref 63 by permission of Wiley-VCH.)...

The alkaloid Nigellicine proved to be the pyridazino[l,2-u]indazolium-l 1-carboxylate (234) and forms yellow crystals (Scheme 77). It was isolated from the widely distributed herbaceous plant Nigella saliva L., which is used as a spice and for the treatment of various diseases (85TL2759). The structure was determined by an X-ray crystal structure analysis. The carboxylate bond distances are essentially equal (123.3 and 125.6 pm). An intramolecular hydrogen bond was found between the carboxylate oxygen atom and the hydroxy group. In mass spectrometry, the molecular peak was found at mjz —246 (20) and the base peak at mjz —202 which corresponds... 

Chromium, (ri6-benzene)tricarbonyl-stereochemistry nomenclature, 1,131 Chromium complexes, 3,699-948 acetylacetone complex formation, 2,386 exchange reactions, 2,380 amidines, 2,276 bridging ligands, 2,198 chelating ligands, 2,203 anionic oxo halides, 3,944 applications, 6,1014 azo dyes, 6,41 biological effects, 3,947 carbamic acid, 2,450 paddlewheel structure, 2, 451 carboxylic acids, 2,438 trinuclear, 2, 441 carcinogenicity, 3, 947 corroles, 2, 874 crystal structures, 3, 702 cyanides, 3, 703 1,4-diaza-1,3-butadiene, 2,209 1,3-diketones... 

THE STRUCTURE OF THE CARBOXYL GROUP. II. THE CRYSTAL STRUCTURE OF BASIC BERYLLIUM ACETATE... 

Two helices are packed antiparallel in the orthorhombic unit cell. Association of the helices occurs through a series of periodic carboxylate potassium water - carboxylate interactions. An axial projection of the unit-cell contents (Fig. 23b) shows that the helices and guest molecules are closely packed. This is the first crystal structure of a polysaccharide in which all the guest molecules in the unit cell, consistent with the measured fiber density, have been experimentally located from difference electron-density maps. The final / -value is 0.26 for 54 reflections, of which 43 are observed, and it is based on normal scattering factors.15... 

Bis(dicyclohexylammonium) bis(2,6-pyridinedicarboxylato)dibutylstannate is concluded to have sevenfold coordination at the Sn on the basis of its Sn CP/ MAS NMR chemical shift ((5 = —424.9 ppm). The assignment has been corroborated by crystal structure determination of its monohydrate, in which the Sn atom has frflMS-C2SnN04 PBP geometry (Sn-C = 204.0,206.7pm, C-Sn-C = 168.9°). One 2,6-pyiidinedicarboxylato group chelates to the Sn atom (Sn-O = 223.4,226.0 pm Sn-N = 227.9 pm), whereas the other binds through only one carboxyl end (Sn-O = 241.6, 244.1pm). The anhydrous compound displays higher in vitro antitumor activity than those of cisplatin and carboplatin (Table 7). ... 

The molecular mechanism of the enantioselective protonation reaction by antibody 14D9 was revealed by a crystal structure analysis [19[. A catalytic carboxyl group AspH 101 was found at the bottom of the catalytic pocket and found to be necessary for catalysis by mutagenesis to Asn or Ala. The mechanism or protonation involves an overall syn addition of water to the enol ether in a chiral binding pocket ensuring complete enantioselectivity (Figure 3.4). 

In this section, we will neglect the crystal structures of the mesogenic perfluorinated phenyl benzoates [23-27], benzoic acids [6, 28-31], cinnamic acids [7, 32, 33], dicarboxylic acids [34, 35], and cinnamate compounds [8, 36-40]. The single crystal X-ray analyses of chiral mesogenic carboxylates are described in Sect. 6. 

In this section, we will present a short overview of the crystal structures of different mesogenic carboxylate compounds [112-120] which are not... 

In 1997, Sridhar et al. [117] investigated the crystal structure of the mesogenic 4-isothio-cyanato phenyl 4-pentylbicyclo[2,2,2]octane-1-carboxyl-ate. The crystal structure of this compound shows a layered packing along the fl-axis and imbrication along the other two axes. 

Hartung et al. [120] determined the crystal structure of the mesogenic 6-hexylamino-l,2,4,5-tetrazin-3-yl 4-pentyloxybenzoate. The plane of the bridging carboxylic group is inclined to those of the phenyl and the tetrazine rings by 12.1 and 76.3°, respectively. The molecules are arranged in sheets parallel to (021). 

Ito et al. [152] described the crystal structure of 4-[(S)-2-methylbutyl]phe-nyl 4 -hexylbiphenyl-4-carboxylate which shows a smectic A phase and a cholesteric phase. The molecules are arranged in a tilted smectic-like layer structure. Within the layers, the long molecular axes are tilted (30°). However, the compound exhibits no smectic C phase. 

Hori and her collaborators [157, 158] also investigated the crystal structures of 4-[(S)-l-methyl-pentyloxycarbonyl]phenyl 4 -octyloxybiphenyl-4-carboxyl-ate, 4- [ (S)-1 -methyl-hexyloxy-carbonyl] phenyl 4 -octyloxybiphenyl-4-carbox-ylate, and (R)-l-methylheptyl 4-(4 -octyloxy-biphenyl-4-yloxymethylene) benzoate. All three crystal structures are isomorphous with the structure of MHPOBC. 

Zareba et al. [165] described the crystal structure of the chiral 4-(l-methyl-heptyloxycarbonyl)-phenyl 4-heptyloxytolane-4 -carboxylate (C7-tolane) which shows monotropic antiferroelectric and ferroelectric phases. The single-crystal X-ray analysis of this compound shows that the crystal has a smectic-like layer structure composed of largely bent molecules where the chain of the chiral group is almost perpendicular (86°) to the core moiety. Within the layers, the molecules are tilted. The central tolane group of the molecule is roughly planar. 

Fig. 6 Superimposition of inhibitors and key active site residues from crystal structures of oseltamivir carboxylate 18 brown carbons, PDB - 2qwk) and Neu5Ac2en 4 (green carbons, PDB - IfSb) in complex with influenza A virus siaMdase. Note the alternative conformations of the...

However, when the X-ray crystal structure of the MoFe protein was examined, it was clear that homocitrate could not directly hydrogen bond to the histidine, since the carboxylate group and imidazole are stacked parallel to each other in the crystal. Nevertheless, as noted in the previous section, studies on model complexes have suggested that homocitrate can become monodentate during nitrogenase turnover, with the molybdenum carboxylate bond breaking to open up a vacant site at molybdenum suitable for binding N2. 

Spherical vaterite crystals were obtained with 4-mercaptobenzoic acid protected gold nanoparticles as the nucleation template by the carbonate diffusion method [51]. The crystallization of calcium carbonate in the absence of the 4-MBA capped gold nanoparticles resulted in calcite crystals. This indicates that the polymorphs of CaCOj were controlled by the acid-terminated gold nanoparticles. This result indicates that the rigid carboxylic acid structures can play a role in initiating the nucleation of vaterite as in the case of the G4.5 PAMAM dendrimer described above. 

The pH dependence of the rate of modification shows that the pKa of Asp-32 is less than 3.165 It is seen in the high-resolution crystal structures that the carboxyl groups of the two aspartate residues are hydrogen-bonded to each other. This is similar to the ionization of maleic acid, which has pKa values of 1.9 and 6.2 (equation 16.30). 

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