Hydration of α-alanine in aqueous sodium chloride and urea solutions

The hydration number of α-alanine in aqueous urea solutions is greater than in aqueous NaCl solutions; the ratio of the hydration numbers increases from 0.2 (m = 1) to ≈2 (m = 6). Given the same partial volumes of water, the hydration numbers of α-alanine in the two systems are close to each other.     

Amino acid hydration in aqueous magnesium and sodium sulfate solutions

We study the partial volumes of amino acids in aqueous magnesium and sodium sulfate solutions, which have a different effect on the structure of water, and calculate the structural parameters of hydrated complexes of NH ₃ ⁺ and COO^? groups: hydration numbers and water volumes inside and outside the hydration shell. The hydration numbers are given as a sum of the contributions of the interactions in the ternary (water-salt-amino acid) and binary (water-salt) systems.     

Conversion of arylhydrazones of bromonitroformaldehyde and arylazatrinitromethanes to 3-aryl-1,2,3,4-oxatriazolium-5-ones

Mesoionic 3-aryl-1,2,3,4-oxatriazolium-5-ones rather than 1,4-diaryl-dihydro-3,6-dinitro-1,2.,4,5-tetrazines, as previously assumed, are formed when arylhydrazones of bromonitroformaldehyde and arylazotrinitromethanes are heated in acetic acid.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1682–1684, December, 1981.     

Reduction of phosphorus in organic compounds to phosphine under the influence of lithium aluminum hydride

Conclusions The reaction for the reduction of phosphorus-containing organic compounds using lithium aluminum hydride is selective and cannot be used to create a general method for the analysis of phosphorus.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2314–2316, October, 1971.     

1,2,4-Thiadiazoles as promising multifunctional agents for treatment of neurodegenerative diseases

Detailed studies of properties of new 3-substituted 5-anilino-1,2,4-thiadiazoles containing different substituents at position 3 of the thiadiazole ring were carried out, in particular, their esterase profile and antioxidant properties. It was found that the presence in the molecule of 2-aminopropyl fragment determines an efficient and selective inhibition of butyrylcholinesterase as compared to acetylcholinesterase and carboxylesterase, with radical-scavenging activity being weak. The compounds containing a 2-aminopropenyl fragment possess a high radicalscavenging activity, weakly inhibit cholinesterases, and exhibit anticarboxylesterase activity. A wide spectrum of activity of 3-substituted 5-anilino-1,2,4-thiadiazoles as inhibitors of cholinesterases and highly efficient scavengers of free radicals gives a basis for the optimization of structure and development in this series of original agents for therapy of neurodegenerative diseases.     

Interaction of the functional group and hydrocarbon radicals in the L-alanine and glycine amino acids in aqueous NaCl,KCl, and urea solutions at different temperatures

The calorimetric method at temperatures of 288 K, 298 K, and 313 K is used to measure the heats of dissolution of L-α-alanine in aqueous NaCl (m ≤ 5 mol/kg water) and KCl (m ≤ 4 mol/kg water) solutions. The enthalpy and heat capacity coefficients are determined for the pair and triple interactions of alanine with nonaqueous components. Literature data is used to find the contributions from the charged NH ₃ ⁺ and COO^– groups and the hydrocarbon radicals СНСН₃ of L-alanine and СН₂ of glycine in mixtures of water with NaCl, KCl, and urea. A discussion is given of the impact of additives and temperature on the interactions of hydrophilic and hydrophobic amino acids in the said systems.     

Palladium‐Catalyzed Amination of 3,5‐Dihalopyridines – a Convenient Route to New Polyazamacrocycles

Pd‐Catalyzed amination of 3,5‐dibromo‐ and 3,5‐dichloropyridine ( 1a and 1b , resp.) with linear polyamines 2 leads to the formation of a new family of pyridine‐containing macrocycles 3 with an ‘exo’‐oriented pyridine N‐atom (Schemes 1 and 2). The dependence of the macrocycle yield on the nature of the halogen atom, the length of the polyamine chain and C/N atom ratio, and the composition of the catalytic system is studied. The synthesis of mono‐ and bis(5‐halopyridin‐3‐yl)‐substituted polyamines 4, 5, 8, 9 , and of 3,5‐bis(polyamino)‐substituted pyridines 6 is described (Schemes 3 and 4), and the use of these compounds as intermediates on the way to the macrocycles 7, 16 , and 18 with larger cavity (‘cyclodimers’ and ‘cyclotrimers’) is demonstrated (Schemes 5–10).