Ab Initio and in-Crystal Geometry of trans-1,4-Dibromo1,4-dicarboxymethylcyclohexane

The structure of trans-1,4-dibromo-1,4-dicarboxymethylcyclohexane (I) has been determined by single crystal x-ray diffraction. The molecules, located on symmetry centers, are in the rigid chair conformation with the Br and COOCH₃ axial and equatorial, respectively. The molecular geometry observed in the crystal is similar to that calculated for the isolated molecule using ab initio calculations performed at the HF/6-31(d) level. A peculiar arrangement of the carboxymethyl substituents, along with short contacts involving the Br atoms, seem to play a role in the stabilization of the crystalline structure.     

Über einige mikrochemische Unterscheidungsreaktionen für Cocain,Novocain und Stovain

Zusammenfassung Nach kritischem Studium der verschiedenen Reaktionen, die von anderen Autoren zur Identifizierung der drei Alkaloide Cocain, Novocain und Stovain vorgeschlagen worden sind, konnten wir feststellen, welche dieser Reaktionen nicht verwendbar sind, wenn Gemische der genannten Alkaloide vorliegen. Dabei bildet die Reaktion vonWagenaar, welche gestattet, das Novocain mit einer Empfindlichkeit von 1 : 3000 nachzuweisen, eine Ausnahme.Bei Verwendung des neuen Reagens RhCl₃·KJ, das der eine von uns aufgefunden hat, kann man mikrochemisch das Cocain und Stovain mit einer Empfindlichkeit von 1 : 10000 nach weisen und unterscheiden.Diese Reaktion, zusammen mit derjenigen, die das K₂PbJ₄ in Gegenwart derselben Alkaloide zeigt, und die Reaktion vonWagenaar genügen in der analytischen Praxis für die Identifizierung dieser Alkaloide.

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Summary As the result of a critical study of the various reactions which have been proposed by different authors for the identification of the three alkaloids cocaine, novocaine and stovaine, it has been shown which of these reactions cannot be employed when a mixture of the above alkaloids is present.Wagenaar's reaction forms an exception, as this permits the detection of novocaine with a sensitivity of 1:3000.Cocaine and stovaine can be detected and identified with a sensitivity of 1:10000 by making use of the new reagent RhCl₃ KI, discovered by one of the authors.This latter reaction, together with the one based on the behaviour of K₂PbI₄ towards the above alkaloids, andWagenaar's reaction, suffices in analytical practice for their identification

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Résumé Après une étude critique des réactions diverses proposées par d'autres auteurs pour l'identification des trois alcaloides: cocaine, novocaine, stovaine, nous pouvons constater celles qui ne sont pas utilisables dans le cas des mélanges; la réaction deWagenaar y est exceptée car elle permet le décèlement de la novocaine avec une sensibilité de 1:3000.En employant le nouveau réactif RhCl₃·KI trouvé par l'un de nous, on peut déceler et différencier microchimiquement la cocaine et la stovaine avec une sensibilité de 1:10000.Cette réaction, avec celle que donne K₂PbI₄ en présence des mêmes alcaloides, et la réaction deWagenaar suffisent dans la pratique analytique pour l'identification des alcaloides ci-dessus.

     

Ionization-loss stimulated Raman spectroscopy for conformational probing of flexible molecules

The approach of studying structural and dynamical properties of flexible molecules is of substantial interest, as it allows decoding the shapes and intrinsic properties of isolated molecular constituents, which have an influence on the selectivity and functionality in biological processes. Combining quantum computation methods with double resonance or infrared hole burning techniques, mainly covering hydride stretch vibrations, recently led to great progress in understanding the structure of a variety of biological building blocks. Measurements of spectra in the lower frequency range, with relatively compact and convenient laser sources, still pose major challenges. For this reason, the method of ionization-loss stimulated Raman spectroscopy (ILSRS) has been developed and applied for monitoring the spectral features of the 2-phenylethanol prototype. The bands observed in the Raman spectra of its two conformers uniquely identify their structures and are in accord with anharmonic results obtained by density functional theory calculations. These findings point to future opportunities for ILSRS as a powerful conformational probe and set new standards for detailed interrogation of structure and intra- and inter-molecular interactions.     

Complexes containing bridging tin- and germanium-substituted metallocarboxylate ligands from the reactions of Ph3SnOH and Ph3GeOH with Os3(CO)12 in the presence of base

The first examples of bridging tin- and germanium-substituted metallocarboxylate ligands have been obtained from the reactions of Ph₃SnOH and Ph₃GeOH with Os₃(CO)₁₂ under basic conditions. Two products: Os₃(CO)₁₀(μ-η²-O=COSnPh₃)(μ-OMe), 1 (18% yield) and Os₃(CO)₁₀(μ-OMe)(μ-OH), 2 (6.9% yield) were obtained from the reaction of Ph₃SnOH with Os₃(CO)₁₂ in the presence of [Bu₄N]OH in methanol solvent. The compound Os₃(CO)₁₀(μ-η²-O=COGePh₃)(μ-OMe), 3 (7.3% yield) was prepared similarly by using Ph₃GeOH in place of Ph₃SnOH. Each of the products 1-3 were characterized structurally by single-crystal X-ray diffraction analysis. Compounds 1 and 3 each contain an μ-η²-O=COMPh₃, M = Sn or Ge ligand bridging a pair of osmium atoms in a triosmium carbonyl cluster complex.     

On the lack of capillary Mössbauer spectroscopic effect for SnII-containing aqueous solutions trapped in corning Vycor ‘thirsty’ glass

Liquids trapped in the pores of certain silicate glasses (such as Corning Vycor ‘thirsty’ glass) were found to display frozen solutions like behavior at temperatures much higher than their actual freezing point. For example, recoilless γ-resonance absorption was observed for Mössbauer active solutes such as ¹¹⁹Sn and ⁵⁷Fe salts at room temperature (i.e., without the need of quenching). Thus capillary Mössbauer spectroscopy (CMS) proved to be a new and useful experimental tool with great potential in solution chemistry. As part of a research project concerned with the hydrolysis of Sn^II salts, we attempted to perform ¹¹⁹Sn CMS measurements for solutions containing stannous ion in a range of aqueous environments. Somewhat surprisingly, we found that under ambient conditions, Sn^II aqueous liquid solutions, both the acidic and the basic systems, are essentially CMS-silent. This can be attributed to the strong temperature dependence of Lamb–Mössbauer factor of Sn^II species, which may result in the complete disappearance of Mössbauer pattern well below room temperature. These observations can also explain why previous publications concerned with the use of CMS dealt exclusively with Sn^IV and not with Sn^II containing liquids.     

Gas chromatography/tandem mass spectrometry method for the simultaneous analysis of 19 brominated compounds in environmental and biological samples

A methodology for the simultaneous analysis of eight polybrominated diphenyl ethers (PBDEs); eight methoxylated PBDEs (MeO-PBDEs); and three emerging flame retardants, hexabromobenzene (HBB), pentabromoethyl benzene (PBEB), and decabromodiphenyl ethane (DBDPE) by gas chromatography coupled to tandem mass spectrometry (GC-MS-MS) was developed for two environmental matrices (sediment and sludge) and three biological matrices (fish, dolphin blubber, and bird eggs). The use of selective reaction monitoring (SRM) allows a high selectivity, which is critical in the analysis of complex samples like blubber. Analytical parameters such as linearity, reproducibility, or accuracy were evaluated. Method limits of detection and quantification were evaluated and compared with GC-EI-MS and GC-NCI-MS. Method detection limits were valid for the environmental analysis in all cases, with values between 0.01 and 1.65 ng/g dw for sediment, 0.05 and 2.78 ng/g dw for sludge, 0.04 and 10.6 ng/g lw for fish, 0.01 and 1.11 ng/g lw for dolphin blubber, and 0.03 and 3.20 ng/g lw for bird eggs. The developed method was applied to five samples of each matrix. PBDEs were detected in all samples, while MeO-PBDEs were only detected in dolphin blubber. DBDPE was detected in sediment and sludge.     

Phytochemical,antimicrobial and antiquorum-sensing studies of pulicaria undulata L.: a revision on the structure of 1β,2α,3β,19α,23-pentahydroxy-urs-12-en-28-oic acid

Abstract

Phytochemical study of the aerial part of Pulicaria undulata L. led to the isolation of nine compounds. The structure of 1β,2α,3β,19α,23-pentahydroxy-urs-12-en-28-oic acid (4) was revised and confirmation of the stereochemical configuration of the hydroxyl groups was established using NOESY and selective decoupling experiments. The other compounds were identified as 1,2-dehydro-1,10α-dihydropseudoivalin (1), axillarin (2), grandifloric acid-15-β-glucoside (3), myrianthic acid (5), caffeic acid (6), quercetin (7), paniculoside IV (8) and caffeic anhydride (9). The structures were characterized by 1?D, 2?D NMR spectroscopy and confirmed with HRMS. Antimicrobial and antiquorum-sensing activities of the different extracts and isolated compounds of the plant were investigated. Generally, the phenolic rather than the terpenoidal compounds exhibited remarkable antimicrobial and antiquorum-sensing activity.

     

Polymerization in the crystalline state. VIII. Polymerization in N-carboxy anhydrides of γ-benzyl glutamate, γ-methyl glutamate,and ϵ-carbobenzoxylysine

The kinetics of the solid-state polymerization of the N-carboxy anhydrides (NCA) of the L - and racemic forms of γ-benzyl glutamate (BG), γ-methyl glutamate (MG), and ?-carbobenzoxylysine (CL) were studied as a function of temperature and aqueous vapor pressure. The reaction of the L -forms of BG and MG was characterized by an induction period, while the CL derivative reached its maximum polymerization rate at the outset of the reaction. Water vapor had only a minor effect in accelerating the reaction and reducing the chain length of the polypeptides formed. The racemic monomers were found to have different crystal structures from those of the L -isomers and the racemic MG and CL derivatives polymerized much more slowly than the corresponding optically active crystals. All polymers gave diffuse x-ray diffraction patterns. Infrared spectra of the L -polypeptides showed that they were largely in the α-helical form. The polymer derived from the racemic BG–NCA had a content of α-helical material which suggested that it consisted of polypeptides with long blocks of D and L residues.     

Acyclic chelate with ideal properties for (68)Ga PET imaging agent elaboration

We have investigated novel bifunctional chelate alternatives to the aminocarboxylate macrocycles NOTA (N(3)O(3)) or DOTA (N(4)O(4)) for application of radioisotopes of Ga to diagnostic nuclear medicine and have found that the linear N(4)O(2) chelate H(2)dedpa coordinates (67)Ga quantitatively to form [(67)Ga(dedpa)](+) after 10 min at RT. Concentration-dependent coordination to H(2)dedpa of either (68)Ga or (67)Ga showed quantitative conversion to the desired products with ligand concentrations as low as 10(-7) M. With (68)Ga, specific activities as high as 9.8 mCi nmol(-1) were obtained without purification. In a 2 h competition experiment against human apo-transferrin, [(67)Ga(dedpa)](+) showed no decomposition. Two bifunctional versions of H(2)dedpa are also described, and these both coordinate to (67)Ga at RT within 10 min. Complete syntheses, characterizations, labeling studies, and biodistribution profiles of the (67)Ga complexes are presented for the new platform chelates. The stability of these platform chelates is higher than that of DOTA.