Neutron activation analysis of trace metals in the hair and organs of small animals treated chronically with Hg and Mn

For the purpose of studying the secretion of exogenous toxic metals into hair, relation between their concentrations in hair and those in organs, and the metal shift, Hg or Mn was orally administered to guinea pigs for protracted periods, the distributions of metals in hair and organs were examined by means of neutron activation analysis. It was found that the administration of Hg at high dose resulted in abnormally high Hg levels in hair from the 2nd dosing week and in organs after 25 week dosing, and in a reduced motor activity after 25 week administration. There occurred metal shifts in hair as well. Administration of Mn at high doses, on the other hand, showed no such biological influences, although a dose-dependent increase of Mn in hair was detected with time.     

Nonameric porphyrin assemblies--formation and intra-assembly energy transfer reactions

The nonameric porphyrin assemblies constructed with the series of free base tetraphenylporphyrins Pn having four pyrazine moieties linked with alkyl chains of different lengths, (CH2)n (n = 1, 5, 9, 17, 30), and dimeric [meso-tetrakis(2-carboxy-4-nonylphenyl)porphyrinato]zinc(II), ZnP2, show the effective light-collection effect and the typical Forster-type energy transfer from ZnP2 to Pn.     

Template-directed dynamic synthesis of mechanically interlocked dendrimers

The versatility and efficiency of dynamic covalent chemistry (DCC) has been exploited in the convergent synthesis of mechanically interlocked dendrimers that are based upon the mutual recognition expressed between secondary dialkylammonium ions and crown ether-like macrocycles. Reversible imine bond formation is employed to clip two acyclic fragments, one of them a diformylpyridine unit bearing a dendritic side chain, and the other a complementary dianiline in the shape of the di(o-aminophenyl)ether of tetraethylene glycol, around each arm of a tritopic trisammonium ion core, thereby affording a branched [4]rotaxane. This template-directed strategy has been demonstrated to work in very high yields (>90%) with successive generations (G0-G2) of a modified Fréchet-type dendritic wedge attached to the 4-position of the diformylpyridine unit. Reduction of these dynamic dendritic systems is achieved upon treatment with borane.THF and results in kinetically stable compounds. The inherent modularity of the overall process should allow for the rapid and straightforward access to many other analogous mechanically interlocked systems in which either the branched core or the dendritic periphery can be modified to suit the needs of any given application of these molecules. Indeed, the dynamic nature of the initial thermodynamically mediated assembly could be utilized in order to amplify particular products from a potential library as a result of a selective recognition process.     

Sustained-release phenylpropanolamine hydrochloride bilayer caplets containing the hydroxypropylmethylcellulose 2208 matrix. II. Effects of filling order in bilayer compression and manufacturing method of the prolonged-release layer on compactibility of bilayer caplets

The purpose of this study was to establish the manufacturing method of the formulated bilayer caplets containing the hydroxypropylmethylcellulose 2208 (HPMC2208) matrix without lamination. In manufacturing the bilayer caplets containing the HPMC2208 (Metolose 90SH4000) matrix, some bilayer caplets were cracked. We found that cracking of bilayer caplets is not the separation of two layers, but lamination of the prolonged-release layer. It was assumed that Metolose 90SH4000 causes lamination of the prolonged-release layer. Two factors, roller compaction pressure on dry granulation of the prolonged-release layer and filling order of the prolonged-release layer in bilayer compression, were related to lamination of bilayer caplets. The compactibility of the prolonged-release layer decrease with an increase in roller compaction pressure on dry granulation. The compactibility of the prolonged-release layer manufactured by direct compression is superior to that manufactured by dry granulation. The compactibility of the prolonged-release layer in the shape of the second layer, convexo-concave, is superior to that in the shape of the first layer, convexo-convex. This is due to the fact that the density distribution inside the compact in the shape of convexo-concave was more uniform than that in the shape of convexo-convex. The manufacturing method of the formulated bilayer caplets having the prolonged-release layer whose Metolose 90SH4000 content is 60% without lamination is as follows: the prolonged-release layer manufactured by direct compression is fed as the second layer in bilayer compression.     

Total Synthesis of Plakortone B

Plakortone B is a naturally occurring bicyclic[3.3.0]furanolactone compound with attractive bioactivities. Although the relative configuration of plakortone B’s central core had been established by NMR spectroscopic methods, the absolute configuration of its four stereocenters remained unknown. In the present paper, all four possible isomers of plakortone B were synthesized and one of these molecules was found to be identical with the natural plakortone B on the basis of ¹H, ¹³C NMR spectra and specific rotation comparisons. Thus, the absolute configuration of the natural plakortone B was determined to be (3S,4S,6R,10R).     

Environmental effects on the enhancement in natural and damaged DNA nucleobase acidity because of discrete hydrogen-bonding interactions

The present study uses density functional theory to carefully consider the effects of the environment on the enhancement in (natural and damaged) DNA nucleobase acidities because of multiple hydrogen-bonding interactions. Although interactions with one small molecule can increase the acidity of the nucleobases by up to 60 kJ mol-1 in the gas phase, the maximum increase in enzymatic-like environments is expected to be approximately 40 kJ mol-1, which reduces to approximately 30 kJ mol-1 in water. Furthermore, the calculated (simultaneous) effects of two, three, or four molecules are increasingly less than the sum of the individual (additive) effects with an increase in the number and acidity of the small molecules bound or the dielectric constant of the solvent. Regardless of these trends, our calculations reveal that additional hydrogen-bonding interactions will have a significant effect on nucleobase acidity in a variety of environments, where the exact magnitude of the effect depends on the properties of the small molecule bound, the nucleobase binding site, and the solvent. The maximum increase in nucleobase acidity because of interactions with up to four small molecules is approximately 80 kJ mol-1 in enzymatic-like environments (or 65 kJ mol-1 in water). These results suggest that hydrogen-bonding interactions likely play an important role in many biological processes by changing the physical and chemical properties of the nucleobases.     

Palladium(II)-catalyzed carboxylation of benzene and other aromatic compounds with carbon monoxide under very mild conditions

Aromatic compounds such as benzene, toluene, chlorobenzene, anisole, and naphthalene were carboxylated by palladium(II) acetate catalyst with carbon monoxide in the presence of potassium peroxodisulfate in trifluoroacetic acid (TFA) at room temperature under atmospheric pressure. The aromatic carboxylic acids were formed in good yields; for example, the carboxylation of benzene with carbon monoxide proceeds quantitatively under the optimal conditions.     

Dichloro­oxo(quinoline‐8‐thiolato‐κ2N,S)(triphenyl­phosphine oxide‐κO)rhenium(V) acetone solvate

The complex mol­ecule in the title compound, [Re(C₉H₆NS)Cl₂O(C₁₈H₁₅OP)]·C₃H₆O, has distorted octa­hedral geometry. The Re=O bond occupies the position trans to the triphenyl­phosphine oxide O atom. The Re—Cl bond trans to the thiol­ate S atom is longer than that trans to the quinoline N atom, implying a stronger trans influence of the S atom. Intra‐ and inter­molecular π–π inter­actions are also observed between the π rings in the complex.