Synthesis of pyridine-based polyaminocarboxylic ligands bearing a thioalkyl anchor

A bicyclic tetraazatriacetic chelating agent containing a thioalkyl pendant group was prepared. Four synthetic routes have been investigated via a Mitsunobu reaction from 2,4-[bishydroxymethyl]-3-hydroxy-pyridine 1. Deprotection of trityl thioether compound 5c led to ligand 6c in 22% overall yield from the starting 3-hydroxypyridine.     

Electron density analyses of opioids: a comparative study

The electron densities of five morphine related molecules (codeine, diprenorphine, naltrexone in the neutral and protonated states, and dextromethorphan) were determined from high-resolution X-ray diffraction experiments (Mo Kalpha and synchrotron primary radiation) at low temperature and CCD area detection techniques. Bond topological analyses were applied, and a partitioning of the molecules into atomic regions making use of Bader's zero flux surfaces yielded atomic volumes and charges. The obtained atom and bonding properties were compared to the results of a previous experimental study of morphine and to theoretical calculations. Experimental and theoretical properties for all chemically equivalent bonds agree within an uncertainty range as is otherwise seen for different theoretical calculations. Hence, the transferability of chemically equivalent submolecular properties, being a key issue of the atoms in molecules (AIM) theory, has been verified experimentally in this class of chemically related molecules. On the other hand, topological differences could clearly be verified in regions with different chemical environments. Electron density differences between the two forms of naltrexone were examined and made visible in an extended region around the nitrogen atom which is once in a neutral state and once in a positively charged state.     

Effect of the metal environment on the ferromagnetic interaction in the Co-NC-W pairs of octacyanotungstate(V)-Cobalt(II) three-dimensional networks

State of the art CASSCF and CASPT2 calculations have been performed to elucidate the nature of ferromagnetism of CoII-NC-WV pairs in the three-dimensional compound [[WV(CN)2]2[(micro-CN)4CoII(H2O)2]3.4H2O]n, which has been recently synthesized and investigated by a number of experimental techniques (Herrera, J. M.; Bleuzen, A.; Dromzée, Y.; Julve, M.; Lloret, F.; Verdaguer, M. Inorg. Chem. 2003, 42, 7052-7059). In this network, the Co ions are in the high-spin (S = 3/2) state, while the single unpaired electron on the W centers occupies the lowest orbital of the dz2 type of the 5d shell. In agreement with the suggestion made by Herrera et al., we find that the ferromagnetism is due to a certain occupation scheme of the orbitals from the parent octahedral t2g shell on CoII sites, in which the orbital accommodating the unpaired electron is orthogonal to the dz2 orbitals of the surrounding W ions. We investigate the stabilization of such an orbital configuration on the Co sites and find that it cannot be achieved in the ground state of isolated mononuclear fragments [CoII(NC)4(OH2)2]2- for any conformations of the coordinated water molecules and Co-N-C bond angles. On the other hand, it is stabilized by the interaction of the complex with neighboring W ions, which are simulated here by effective potentials. The calculated exchange coupling constants for the CoII-NC-WV binuclear fragments are in reasonable agreement with the measured Curie-Weiss constant for this compound. As additional evidence for the inferred electronic configuration on the Co sites, the ligand-field transitions, the temperature-dependent magnetic susceptibility, and the field-dependent low-temperature magnetization, simulated ab initio for the mononuclear Co fragments, are in agreement with the available data for another compound [WIV[(micro-CN)4-CoII(H2O)2]2.4H2O]n containing diamagnetic W and high-spin Co ions in an isostructural environment.     

Conformationally restricted (+)-cacospongionolide B analogues. Influence on secretory phospholipase A2 inhibition

A new approach to (+)-cacospongionolide was developed to access conformationally restricted variants of the natural product. The flexible aliphatic region between the decalin and side chain portion of the natural product was replaced with alkenyl and alkynyl linkers to probe the influence of structural rigidity in the inhibition of secretary phospholipase A2 (sPLA2). It was found that when the aliphatic section is replaced with a Z-olefin or an alkyne, sPLA2 inhibitory activity suffered relative to the natural product; however, an E-olefin-containing analogue led to an enhanced activity. These results suggest that preferred sPLA2 binding conformation of the natural product is similar to the geometry of the E-olefin-containing analogue.     

Patterned burst-pulse vocalizations of the northern right whale dolphin, Lissodelphis borealis

Vocalizations from the northern right whale dolphin, Lissodelphis borealis, were recorded during a combined visual and acoustic shipboard survey of cetacean populations off the west coast of the United States. Seven of twenty single-species schools of L. borealis produced click and pulsed vocalizations. No whistles were detected during any of the encounters. Clicks associated with burst-pulse vocalizations were lower in frequency and shorter in duration than clicks associated with echolocation. All burst-pulse sounds were produced in a series containing 6-18 individual burst-pulses. These burst-pulse series were stereotyped and repeated. A total of eight unique burst-pulse series were detected. Variation in the temporal characteristics of like units compared across repeated series was less than variation among all burst-pulses. These stereotyped burst-pulse series may play a similar communicative role as do stereotyped whistles found in other delphinid species.     

Asymptotic behavior and Hamiltonian analysis of anti-de Sitter gravity coupled to scalar fields

We examine anti-de Sitter gravity minimally coupled to a self-interacting scalar field in D ? 4 dimensions when the mass of the scalar field is in the range . Here, l is the AdS radius, and is the Breitenlohner-Freedman mass. We show that even though the scalar field generically has a slow fall-off at infinity which back reacts on the metric so as to modify its standard asymptotic behavior, one can still formulate asymptotic conditions (i) that are anti-de Sitter invariant; and (ii) that allows the construction of well-defined and finite Hamiltonian generators for all elements of the anti-de Sitter algebra. This requires imposing a functional relationship on the coefficients a, b that control the two independent terms in the asymptotic expansion of the scalar field. The anti-de Sitter charges are found to involve a scalar field contribution. Subtleties associated with the self-interactions of the scalar field as well as its gravitational back reaction, not discussed in previous treatments, are explicitly analyzed. In particular, it is shown that the fields develop extra logarithmic branches for specific values of the scalar field mass (in addition to the known logarithmic branch at the B-F bound).     

Controlling surfaces and interfaces with functional polymers: Preparation and functionalization of dendritic–linear block copolymers via metal catalyzed “living” free radical polymerization

The preparation and chemical modification of dendritic–linear block copolymers with surface functionalized dendritic components are presented. Isophthalate ester-functionalized dendrons featuring benzylic halide groups at their focal points have been used for the metal catalyzed “living” radical polymerization of styrene. The molecular weight of the dendritic–linear block copolymers determined by MALDI-TOF and Size Exclusion Chromatography was found to be accurately controlled up to molecular weights of ca. 30,000 a.m.u., with polydispersities less than 1.2. Subsequent functional group modifications of the peripheral ethyl ester groups of the dendritic block have been successfully carried out leading to carboxylic acids, butyl amides, benzyl alcohols, benzyl halides, and also accelerated generation growth via transesterification with a first generation dendritic alcohol. Several of these new dendritic–linear block copolymers exhibit interesting aggregation characteristics as evidenced by ¹H-NMR spectroscopic studies. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1–10, 1998