Circular dichroism of quinoid pigments from Far Eastern representatives of the family Boraginaceae

The electronic absorption and circular dichroism (CD) spectra of ten natural and modified quinoid pigments are described. An assignment has been made of the dichroic absorption in the 250–600 nm region of the CD spectra of the pigments investigated. It has been shown that in the solution of stereochemical questions for such compounds the most informative region of the CD spectrum is the 250–350 nm interval.Pacific Ocean Institute of Bioorganic Chemistry, Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 568–573, September–October, 1983.     

Investigation of the circular dichroism spectra of bromine-substituted nucleic acid fragments I. Circular dichroism spectra of 8-bromine-substituted purine nucleotides

Summary The CD spectra of 8-bromo-AMP, 8-bromo-dAMP, 8-bromo-GMP, and 8-bromo-dGMP in acid, neutral, and alkaline media and, in some cases, in methanol have been obtained. In the 200–300 nm region three Cotton effects have been recorded which correspond to -* in the B_2u, B_1u, and E_1ua bands (280–265, 240–250, and 200–220 nm, respectively). The CD spectra obtained differ from the spectra known in the literature for unbrominated compounds of this class. It has been shown that in ribonucleotides the syn conformation is stabilized by the formation of an intramolecular hydrogen bond with the participation of the ribose 2-hydroxyl and the N₃ atom of the purine base. The 5-phosphate group in the molecule of a purine nucloside of the syn type changes the CD profile, particularly in the short-wave region of the spectrum, as compared with the CD spectra of the unbrominated analogs given in the literature.Institute of Molecular Genetics, Academy of Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 199–204, March–April, 1979.     

Circular dichroism and stereochemistry of the C-20 and C-22 asymmetric centers of 17-isoxazolinyl- and 20-hydroxy-20-isoxazolinylsteroids

The CD spectra of a number stereoisomeric isoxazolinylsteroids have been investigated. Starting from established rules, it has been shown that this method can be used to determine the configurations of the C-20 and C-22 centers of the 17- and 20-isoxazolinylsteroids studied.The numbering of the atoms of the isoxazoline ring corresponds to the numbering of the side-chain of cholesterol.Institute of Bioorganic Chemistry, Belarus Academy of Sciences, Minsk. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 391–397, May–June, 1994.     

Triterpene glycosides ofAstragalus and their genins. XXI. Circular dichroism of cycloartane ketones

The CD spectra of a number of natural and synthetic cycloartane ketones have been studied. The influence of 6-hydroxy group on the Cotton effect due to a 3-keto function has been found. The Cotton effect has been determined for 6-oxo-and 11-oxocycloartanes.Institute of the Chemistry of Plant Substances of the Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 614–628, September–October, 1986.     

Circular dichroism and configuration of (−)-1-methyl-1,2,3,4,tetrahydroisoquinoline

In the CD (circular dichroism) spectra of (–)-1-methyl-1,2,3,4, tetrahydroisoquinoline, three CE (Cotton effects) are observed in the 300–200 nm region that are due to the absorption bands of the aromatic chromophore. The synthesis of this substance from (S)(–)--phenylethylamine and the CD spectra confirm its (S)-configuration.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1238–1240, September, 1987.     

Investigation of the circular dichromism spectra of bromine-substituted nucleic acid fragments II. Circular dichroism spectra of 5-bromine-substituted pyrimidine nucleotides

Summary The CD spectra of 5-bromine-substituted derivatives of nucelotides of uracil and cytosine, namely the ribo- and 2-deoxyribonucleoside 5-monophosphates, have been obtained in neutral, acid, alkaline, and alcoholic solutions. Three CEs have been recorded in the 220–300 nm region, corresponding to -* transitions in the B_2u, B_1u, and E_1ua bands. It has been concluded that an intramolecular hydrogen bond exists between 0–2 and the 2-hydroxyl in the 5-bromine-substituted ribonucleotides of uridine and cytidine. A transition of the conformational type localized at a pH equal to the pK value of the heterocyclic base has been detected for 5-bromo-UMP and UMP. On comparing the main characteristic of the CD spectra of the compounds investigated with the spectra of the unbrominated analogs given in the literature, it has been concluded that the halogenation of a pyrimidine base in position 5 does not fundamentally change the ratio of the most probable rotational stereomers, and the compounds investigated have the anti conformation in solution.Institute of Molecular Genetics, Academy of Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 204–208, March–April, 1979.     

Circular dichroism of veralosidine and its derivatives

Summary On the basis of their CD spectra, the alkaloids veralosidine, veralosine, veralosinine, and veralosidinine have been assigned to the 25S series.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 623–625, September–October, 1976.     

Circular dichroism of the alkaloids ofPetilium raddeanum

The circular dichroism (CD) method has been used for studying the stereochemistry of steroid alkaloids containing an azomethine ring — petiline and petisine. In the CD spectrum of petiline a Cotton effect (CE) is observed in the 235 nm region which is due to a n * transition in the azomethine chromophore. The negative sign of this CE shows the 25S configuration in petiline. An analysis of CD spectra has shown that the 25S configuration is retained when petiline is oxidized to petisine.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 345–347, May–June, 1986.     

Circular dichroism of acetylated methyl glycosides

The circular dichroism (CD) spectra of a number of acetylated methyl glycosides, from mono-to tetra-O-acetates, have been obtained. The signs of the CD maxima of the n-* transitions (210–215 nm) of the O-acetate groups have been predicted, and these predictions coincide with the figures obtained experimentally.Pacific Ocean Institute of Bioorganic Chemistry of the Far Eastern Scientific Center, Academy of Sciences of the USSR, Vladivostok. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 54–56, January–February, 1980.     

Circular dichroism of some sesquiterpene lactones of the germacrane type

The CD spectra of a series of germacranolides have been considered, and the parameters of the Cotton effects observed have been correlated with the stereochemistries of the compounds studied. The applicability for germanocranolides of the Waddell-Stocklin-Geissman rule is discussed.Deceased.Institute of the Chemistry of Plant Substances of the Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 176–179, March–April, 1986.     

Chemical-ionization mass spectra of diterpene alkaloids

The chemical-ionization spectra of diterpene alkaloids have been investigated for the first time with the recording of positive and negative ions [Cl(+) and (–)). A comparison has been made of the CI(+) spectra with the EI and SIMS spectra. It has been shown that the nature of the CI(+) and (–) spectra depends greatly on the type and position of substituents in the lycoctonine skeleton.Deceased.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 89 14 75. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 114–122, January-February, 1995. Original article submitted October 31, 1994.     

Calculations of silicooxygen ring vibration frequencies

In the work model calculations of the vibrations of ideally isolated silicooxygen rings (using PM3 method) have been carried out. three-, four-, and six-membered rings have been considered. It has been found that that the three-membered silicooxygen rings are flat and practically undeformed showing D_3h symmetry. The rings of higher number of ring members (i.e. n>3) are deformed to some extent. The deformation reveals itself most significantly in the Si–O–Si bond angles distribution. In the case of all the rings the bridging Si–O–Si bonds are ca. 0.02–0.04 Å shorter than the non-bridging Si–O⁻ bonds. Hypothetical IR spectra for all the rings considered have been also calculated. Analysis of these hypothetical spectra leads to the conclusion that the whole spectrum can be divided into four wavenumbers regions, 1200–1100 cm⁻¹ stretching Si–O(Si) vibrations; 1000–800 cm⁻¹ stretching Si–O⁻ vibrations; 800–600 cm⁻¹; the region in which a band characteristic of silicooxygen rings appears, and below 600 cm⁻¹ bending ⁻O–Si–O⁻ and (Si)O–Si–O(Si). It has been also found that as the number of ring members increases the ‘ring band’ shifts to lower wavenumbers: 725 cm⁻¹ for three-membered rings, 650 cm⁻¹ for four-membered rings and 610 cm⁻¹ for six-membered rings. Calculated spectra have been compared with the experimental spectra of cyclosilicates. They showed good agreement in the 1200–600 cm⁻¹ region. In the experimental spectra as well as in the calculated ones, with increasing the number of ring members the ‘ring band’ shifts towards lower wavenumbers.     

Mass-spectrometric investigation of some new derivatives of the alkaloid lupinine

The mass spectra of some new derivatives of lupinine have been studied with the use of the spectra of metastable ions. On the basis of the results of an investigation of DADI spectra it has been shown that in the formation of low-mass quinolizidine ions the ions with m/z 152–150 are of considerable importance.A. S. Sadykov Institute of Biororganic Chemistry, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 508–512, July–August, 1990.     

Alkaloids of a new type fromSophora alopecuroides L.

Summary The structures of aloperine and allylaloperine (fromSophora alopecuroides L.) — alkaloids of a new structural type for the genusSophora — have been established by chemical and spectral methods. A number of parameters, NMR spectra, and mass spectra characterizing this class of compounds has been obtained. The partial synthesis of allylaloperine has been performed.All-Union Scientific-Research Institute of Medicinal Plants. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 30–37, January–February, 1975.     

Choice of the best region for channel-by-channel summation of estimating the intensity of single photopeaks

The influence of partial peak width integration on the statistical error has been investigated. It has been shown that integration of the central photopeak part —±(0.55–0.64) FWHM for narrow peaks and ±(0.50–0.53) FWHM for wide peaks-allows to decrease the statistical error 1.5–2.0 times in comparision with the TPA method. The results obtained are valid both for real photopeaks and for smoothed spectra. The theoretical results have been confirmed by experimental data.     

Synthesis,spectroscopic and magnetic properties of methoxo- bridged copper(II) complexes with 2-amino-4-methylpyridine as the ligand

Three new methoxo-bridged copper(II) complexes with 2-amino-4- methylpyridine as the ligand have been synthesized and characterized by elemental analyses, FTIR and electronic spectra, and by their magnetic properties. The complexes exhibit strong antiferromagnetic interactions at room temperature. The u.v.-vis spectra exhibits three absorption bands, which can attributed to d–d, L–M and –* transitions. The i.r. spectra indicates Cu2O2 ring vibrations in the 580–530cm–1 range. The magnetic properties of the [Cu2(2-amino-4-methylpyridine)4(O- Me)2](ClO4)2 complex has been investigated in the 5–270K range and a singlet-triplet energy gap (–2J) of 67cm–1 was observed. All complexes in the solid state are e.p.r.-silent and show no triplet spectrum; in fact a weak signal due to a monomeric impurity are observed. Frozen solution e.p.r. spectra suggest that the complexes dissociate when dissolved in DMF or DMSO.     

Chemical ionization mass spectra of natural monohydroxy- and monoacyloxy-substituted dihydropyranocoumarins and dihydrofurocoumarins

Summary The chemical ionization mass spectra of ten compounds of the group of natural monohydroxy and monoacyloxy derivatives of dihydropyranocoumarins and dihydrofurocoumarins have been studied. Their difference from the electron impact mass spectra has been shown. The structural-analytical possibilities of the method of chemical ionization for this series of substances has been determined.M. V. Lomonosov Moscow State University. Patrice Lumumba International Friendship University, Moscow. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 508–512, July–August, 1977.     

Far-infrared spectrum,barrier to internal rotation,ro structure,and ab initio calculations for acetylacetylene

The far-infrared spectrum has been recorded from 50 to 360 cm^–1 at a resolution of 0.10 cm^–1 for acetyiacetylene (1-butyne-3-one], CH₃C(O)CCH. The fundamental methyl torsion has been observed at 117.94 cm^–1, from which a periodic barrier to internal rotation has been calculated to be 346 cm^–1 (989 cal mol^–1]. Infrared spectra (3500-50 cm^–1] of the gas and solid and the Raman spectra (3500-100 cm^–1) of the gas, liquid, and solid are reported. Utilizing previously reported rotational constants for three isotopic species,r _o structural parameters have been determined for the heavy-atom skeleton. The fundamental vibrational frequencies, barrier to internal rotation, and structural parameters that have been obtained experimentally are compared to those obtained from ab initio Hartree-Fock calculations employing 3-21G, 6-31G, and DZ basis sets and to the corresponding quantities for some similar molecules.