Charge-transfer bands and conformation of palladium chloride solvates in certain donor solvents

Theoretical and Experimental Chemistry -     

QSAR models for analgesic activity prediction of terpenes and their derivatives

Structural Chemistry - In the present study, quantitative structure-activity relationship (QSAR) models were developed to predict analgesic activity of some mono-/bicyclic terpenoids and their...     

Molecular motions in alicyclic compounds

Carbon-13 spin-lattice relaxation times and chemical shifts are reported for a number of cyclic alcohols and the corresponding methyl ethers. The overall rotation of the alcohols was found to be considerably more anisotropic than that of the methyl ethers. Anisotropic motion becomes less pronounced in both series as ring size increases.     

Optical activity in the biaryl series

The relationship between the CD spectra of the chiral biaryls and their stereochemical configuration, as a function of the dihedral angle between the molecular planes of the aromatic moieties, has been investigated for biphenyl, 1,1′-binaphthyl, 1,1′-bianthryl and 9,9′-bianthryl in the exciton approximation and, for the 1,1′-binaphthyls, in the π-SCF approximation. Both methods provide unambiguous assignments of absolute configuration except for biaryls with a critical dihedral angle of π/2 in those with effective D_data2 chromophoric symmetry, or 100–110° in the case of the 1,1′-binaphthyls.     

The high-temperature alicyclic ring contraction of 1,1-dichloroperfluorotetralin and the alicyclic ring opening of 1,1-dichloroperfluorobenzocyclobutene

The pyrolysis of 1,1-dichloroperfluorotetralin (4) in a stream of argon gives a mixture contained perfluoro-1-methyleneindan (1), perfluoro-3-methylindene (6), 1,1-dichloroperfluoroindan (2) and perfluoroindene (7), while copyrolysis of tetralin 4 with CHClF₂ gives a mixture of compounds 1, 6 in the absence of compounds 2 and 7. 1-Chloro-2-(1-chloro-2,2-difluorovinyl)-3,4,5,6-tetrafluorobenzene (12) is formed in the pyrolysis of 1,1-dichloroperfluorobenzocyclobutene (5) in a stream of argon as well as in a stream of CHClF₂.     

Polarography of alicyclic compounds

A review of the polarography of alicyclic compounds is presented.     

Demonstration of the ring conformation in polyproline by the Raman optical activity

Raman and Raman optical activity (ROA) spectra of poly-L-proline were recorded in a wide frequency range and analyzed with respect to the proline side chain conformation. The analysis was based on comparison to ab initio simulations of spectral band positions and intensities. The presence of two conformer states of the five-member ring was found, approximately equally populated in the polypeptide. Additionally, Raman and ROA spectral shapes indicated that the peptide adopts the polyproline II helical conformation, in both aqueous and TFE solutions. The helix, however, is perturbed by fluctuations, which affects the vibrational coupling among amino acid residues and broadens the ROA bands. Contributions of the side and main peptide chains to the polyproline ROA intensities have comparable magnitudes. Thus understanding of the origins of both signals is important for determination of the peptide structure by ROA.     

Optical properties of certain steroid hormones and related compounds

Summary Optical properties of one adrenal cortex, one corpus luteum, two testes, six gluco corticoid, and three unclassified steroids were determined. These data afford a positive identification of these compounds with only minute amounts of material.

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Zusammenfassung Die optischen Eigenschaften von 13 Steroiden (ein Nebennierenrindensteroid, ein Gelhkörpersteroid, zwei Keimdrüsensteroide, sechs Glucocortieosteroide, drei nicht näher klassifizierte Steroide) wurden bestimmt. Die gefundenen Daten ermöglichen die einwandfreie Identifizierung dieser Verbindungen mit sehr geringem Materialaufwand.

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Résumé On a déterminé les propriétés optiques de 13 stéroïdes (un stéroïde cortico-surrénal, un stéroïde du corps jaune, deux stéroïdes des glandes génitales, six glueocorticostéroïdes, trois stéroïdes n'appartenant pas aux classifications précédentes). Les données trouvées permettent l'identification rigoureuse de ces composés sur très peu de substance.

     

Assessing the antioxidant activity of certain drugs in oxidation of emulsions

The results from developing a kinetic model for testing water-soluble antioxidants by examining the micelle formation and oxidation kinetics of water-emulsion ethyl oleate and methyl linoleate substrates are presented. The optimum composition of the system, the catalyst, and the emulsifying agent are selected. The model is tested using standard, synthetic, and natural antioxidants. Criteria for evaluating the antioxidant’s efficiency are proposed. A more complex mechanism for the action of ionol is presented, along with the possibility of using it as an external standard. The high antioxidant activity of capoten and the manifestation of antioxidant properties by α-tocopherol under selected conditions are demonstrated.     

Ring-opening polymerization of unsaturated alicyclic compounds

The ring-opening polymerizations of cyclooctene, cyclododecene, 1,5-cyclooctadiene, 1,5,9-cyclododecatriene, 3-methylcyclooctene, and 3-phenylcyclooctene have been carried out by using a two-component catalyst system composed of ethylaluminum dichloride and tungsten hexachloride. NMR and infrared analyses of the respective polymers indicate structures which are consistent with a ring-cleavage mode of propagation. No evidence for double-bond shifts or transannular reactions during the polymerizations of 1,5-cyclooctadiene, 1,5,9-cyclododecatriene, 3-methylcyclooctene, and 3-phenylcyclooctene was found. The polymerizability of substituted, unsaturated, mediumsized alicyclic monomers suggests a convenient method for synthesis of certain perfectly alternating terpolymers. Since polymerizations occurred rapidly with little evolution of heat, it was concluded that entropy is a substantial contributor to the free energy of the ring-opening polymerization of medium-sized, unsaturated alicyclic monomers.     

Raman spectra of some terpenes

Summary Investigation of Raman spectra indicates increase in the interaction between the double bonds as we pass from sylvestrene and isosylvestrene to sylveterpinolene and indicates that the character of the interaction in the last compound is more complex than in 1,3-butadiene and other similar conjugated systems.     

Correlation between the conformation of nucleoside antibiotics and their biological activity

Nucleoside antibiotics, which result as a consequence of minor modifications in pyrimidine and purine nucleosides, exhibit a wide variety of antiviral, antibacterial, antitumor, and cancerostatic properties. The conformational properties of a number of these antibiotics have been investigated by using the quantummechanical PCILO method, and the results indicate that the nucleoside antibiotics and their parent nucleosides have very similar conformational preferences. This similarity is strikingly marked in the situations which prevail in an aqueous medium. As a result, these antibiotics easily get incorporated in growing chains of RNA and DNA by mimicking their parent nucleosides and then bring about the inhibition of protein, RNA, or DNA syntheses. The experimental observations corroborate these deductions, and thus a correlation has been obtained between the conformation and the biological activity of nucleoside antibiotics; it is the striking conformational similarity between the nucleoside antibiotics and their parent nucleosides which gives rise to their biological activity. The PCILO investigations carried out on two 3-deazapurine nucleosides demonstrate that the converse of the above correlation also holds true.