Novel Peptide Chemistry in Terrestrial Animals: Natural Luciferin Analogues from the Bioluminescent Earthworm Fridericia heliota

We report isolation and structure elucidation of AsLn5, AsLn7, AsLn11 and AsLn12: novel luciferin analogs from the bioluminescent earthworm Fridericia heliota. They were found to be highly unusual modified peptides, comprising either of the two tyrosine‐derived chromophores, CompX or CompY and a set of amino acids, including threonine, gamma‐aminobutyric acid, homoarginine, and unsymmetrical N,N‐dimethylarginine. These natural compounds represent a unique peptide chemistry found in terrestrial animals and rise novel questions concerning their biosynthetic origin.     

Functionalized mercaptoacetic and propionic acid amides: synthesis,cyclopalladation features,and catalytic activity of metal complexes

Upon treatment with thiophenol or neomenthyl mercaptane, chloroacetand propionamides with an additional Nor S-donor substituent in the amine part gave new multidentate ligands readily undergoing direct cyclopalladation in the reaction with PdCl₂(NCPh)₂. The realization of κ³-X, N, S-coordination (X = N, S) in the complexes obtained was confirmed by IR and NMR spectroscopy and, in some cases, by single-crystal X-ray crystallography. The evaluation of catalytic activity of the palladocycles in the Suzuki cross-coupling of aryl bromides with PhB(OH)₂ allowed us to establish the principal structure—activity correlations.     

Self-assembled diols: synthesis, structure and dielectric studies

In single-, double-, and triple-chain amphiphilic diols the CONH group was replaced by CON(CH₃) in order to reduce the number of proton donor groups available for intermolecular hydrogen bonding. The resulting three new liquid crystalline diols were studied by DSC, X-ray and dielectric measurements, and show the mesophases SmA, Col_H2 or Cub_I2, depending on the number of decyloxy groups in the hydrophobic part of the molecule. The process of self-assembly to different liquid crystalline phases is well seen in the dielectric spectrum and details of this process are discussed together with results from the X-ray measurements. All the compounds show a high frequency dielectric absorption caused by the dynamics of the network of hydrogen bonds. An additional low frequency process related to the internal dynamics of the columns is seen only in the columnar phase.     

Chemical and electrochemical oxidation of permethylmetallocenecarbaldehydes and the related μ-acyl Os3-clusters

Oxidation of nonamethylmetallocenecarbaldehydes C₅Me₅MC₅Me₄CHO (M=Ru or Os) and the related μ-acyl clusters C₅Me₅MC₅Me₄COOs₃(CO)₁₀H with silver salts afforded η⁶-metallonium cations, whose structures and compositions were confirmed by the data of elemental analysis and¹H,¹⁹F, and¹³C NMR and IR spectroscopy. The results of studies by cyclic voltammetry demonstrated that oxidation of the compounds under study proceeded through 17-electron radical-cationic intermediates and that the μ-acyl Os₃-cluster fragment is a weaker electron-withdrawing group than the CHO group. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 789–793, April, 1999.     

Self‐concentration effects in preparative SEC of mineral electrolytes using nanoporous neutral polymeric sorbents

Separation of mineral electrolytes according to size exclusion mechanism using neutral nanoporous polystyrene sorbents and carbonaceous materials has been examined in detail on hand of HCl and CaCl₂ solutions, taken separately and in the mixture. Phase distribution coefficients of the above electrolytes have been measured under static conditions at different concentrations. The k‐values and their dependence on the concentration were correlated with the elution curves of the components from a chromatographic column. Both the static and dynamic data suggest a strong dependence of the hydration number and effective size of ions on the concentration. Self‐concentration of HCl in small pores and that of CaCl₂ outside of small pores exhibits itself in both static and chromatographic experiments and results from the relocation of the components largely within the volume of the initial mixture. Additional apparent “retention” of HCl in the porous volume of the sorbent in concentrated electrolyte mixtures was shown to be caused by the competition between all ions of the system for hydration water. Increased separation selectivity and enhanced self‐concentration effects for more concentrated mixtures point to preparative and industrial perspectives of size exclusion chromatography (SEC) of complex electrolyte mixtures on nanoporous neutral sorbents.     

The Structures of Bis(3-aminophenyl)phosphinic Acid and Its Derivatives in Solutions

According to IR and ¹⁵N NMR spectroscopy data, bis(3-aminophenyl)phosphinic acid exists in the molecular form in the DMSO and DMF solutions. The molecular and ionic forms are in equilibrium in the solutions of triethylammonium salt of bis(3-aminophenyl)phosphinic acid in DMSO and DMF.     

Interaction of carbon dioxide with zirconocene and hafnocene dihydrides

Zirconocene and hafnocene dihydrides Cp₂MH₂ (M = Zr, Hf) are capable of rapid absorbing carbon dioxide at room temperature and atmospheric pressure in a THF medium. In the case of Cp₂ZrH₂, the reaction results in the cleavage of the C=O bond of a CO₂ molecule to form cyclic trimeric zirconocene oxide [Cp₂ZrO]₃, whose structure was confirmed by analytical and spectral methods as well as by X-ray diffraction study. Small amounts of formaldehyde and methyl formate are found in the organic products of the reaction.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2366–2368, September, 1996.