Characteristics of the mass spectra of ecdysteroids with different numbers of -OR groups

The mass spectra of 15 phytoecdysteroids and acetyl derivatives have been compared. With a decrease in the number of -OR groups, the contribution of cleavages of the bonds of the steroid skeleton increases. 20,22-Diols are characterized by the greatest significance of fragmentation at the C-20–C-22 bond. In all the spectra, clear indications of fragmentation of the side chain at the C-22–C-23, C-23–C-24, and C-24–C-25 bonds are observed.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 518–528, July–August, 1980.     

Determination of the position of the double bonds in the radicals of the fatty acids from hydrogenizates of cottonseed oil

Conclusions 1. Features of the fragmentation of dubinidine and dubinine are explained by the presence of a branched side chain in the dihydrofuran ring.2. The structure of isodubinidine has been elucidated on the basis of its chemical characteristics and UV and mass spectra.Khimiya Prirodnykh Soedinenii, Vol. 6, No. 4, pp. 446–450, 1970     

Phytoecdysones of Serratula III. Mass spectrometric study of the acetates and acetonides of ecdysterone and viticosterone e

Summary Features of the fragmentation of the side chain of the acetates and acetonides of ecdysterone and of viticosterone E have been studied. It has been shown that the presence of an oxygen-containing function at C₂₅ in these compounds imparts to the spectra certain distinguishing features which have analytical value.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 155–158, March–April, 1975.     

Mass-spectrometric investigation of ionophoric derivatives of benzo- and dibenzocrown ethers. 4. 4′-Acyl derivatives of benzo-15-crown-5 and benzo-18-crown-6

The mass spectra of 4-acyl derivatives of benzo-15-crown-5 and benzo-18-crown-6 were studied by the method of direct analysis of the daughter ions (DADI). It was established that the fragmentation of the M⁺ ions of the investigated compounds under electron impact proceeds via the scheme of the McLafferty rearrangement with the simultaneous elimination of ethylene oxide. The degree of occurrence of the McLafferty rearrangement increases with an increase in the length of the side chain.See [3] for communication 3.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 989–901, July, 1987.     

Synthesis and Phosphorylation of 5-Bromoalkyl Derivatives of 2-Furancarboxylic Acid

Esters and nitriles of 5-propyl- and 5-isobutylfuran-2-carboxylic acids are brominated with N-bromosuccinimide in the α position of the side chain. The resulting bromides react with triethyl phosphite to give two products: an alkene and a phosphonate. The alkene fraction increases in going from nitrile to ester and with enhancing branching of the side chain.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 2, 2005, pp. 258–261.Original Russian Text Copyright © 2005 by Pevzner.     

Pectin substances of seaweeds VII. Acetolysis of zosterin

Summary The acetolysis of zosterin has given a fragment based upon a linear rhamnogalacturonan chain with side chains consisting of xylose, arabinose, and apiose residues attached to it.Institute of Biologically Active Substances, Far Eastern Scientific Center, Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 249–252, May–June, 1971.     

Conformational analysis of fluorinated copolymers of tetrafluoroethylene

Conformational analysis of fluorinated copolymers of tetrafluoroethylene (TFE) is performed by taking into account only intramolecular effects (isolated-chain model). In particular, variations of the chain conformation, which are induced by incorporating different side groups, such as –Cl, –CF₃, –OCF₃, –OCF₂CF₃, and –OCF(CF₃)₂, are investigated and discussed with respect to qualitative correlations between conformation, crystal structure, and supramolecular morphology.     

Studies on the series of azoles and azines. 65. Mass spectra of 5-arylidene-, 5-ethoxycarbonylmethylene-hydantoins and their derivatives

The mass spectra of 5-m- and p-substituted benzylidenehydantoins, their thio analogs and 5-carbethoxymethylenehydantoins with a substituent at the -carbon atom of the side chain were studied. The fragmentation of the molecular ions of 5-arylidenehydantoins proceeds in one direction, splitting of the X=C-NR-C=O fragment, irrespective of the substituent in the benzene ring. The peak intensity of the fragmentary ions formed from the molecular ions is linearly dependent on the -constants of the substituent. The direction of the fragmentation of 5-ethoxycarbonylmethylenehydantoins markedly depends on the substituent at the -carbon atom in the side chain that determines the stability of the hydantoin ring and the carboethoxyl group. The fragmentation of these compounds under electron impact proceeds by five paths, related to splitting of fragments O=C₍₂₎NCH₍₄₎=O, C₂H₄, C₂H₅O, C₂H₅OH, and COOC₂H₅.See [1] for Communication 64.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 625–631, May, 1988.     

Dependence of the composition of the products of thermal fragmentation of thiacyanine dyes on the length of their polymethine chain

The pathways of thermal fragmentation of thiacyanine dyes with different lengths of the external polymethine chain were investigated. The results of thermolysis of the thiacyanines are compared with the results of quantum-chemical calculations of their molecules.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 188–192, February, 1982.     

Synthesis and biological properties of a tryptophan-containing fragment of a myelin protein and its analogs

Summary 1. By the azide condensation of fragments followed by the hydrogenolysis of the completely protected nonapeptides formed, the encephalitogenic nonapeptides with the structure Phe-Ser-Try-Gly-Ala-Glu-Gly-Gln-Arc and two of its analogs — the 6-glycine and 5,6-diglycine compounds, have been synthesized.2. It has been shown that the 6-glycine analog induces EAE, i.e., the side chain in position 6 is not essential for the appearance of EAE activity.3. The absence of an encephalitogenic effect in the 5,6-diglycine analog permits the conclusion that the side chain of the alanine-5 makes a contribution to the induction of the disease.4. The N-acetyl derivative of the encephalitogenic nonapeptide retains a high EAE activity.Institute of Molecular Biology and Genetics, Academy of Sciences of the Ukrainian SSR, Kiev. A. V. Palladin Institute of Biochemistry, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 507–517, July–August, 1976.     

Conformations of 2-phenylethanol and its singly hydrated complexes: UV–UV and IR–UV ion-dip spectroscopy

The structures of 2-phenylethanol and its 1:1 water complexes have been investigated by UV–UV holeburning and IR–UV ion-dip spectroscopy, coupled with ab initio computation. The most populated molecular conformer is stabilized by an intramolecular π-type H-bond and its rotational band contours suggest the incidence of vibronic coupling involving motion of the side chain. Its 1:1 water complexes are associated with two distinct structures – water binds either as a proton donor or an acceptor. In the latter, the intramolecular H-bond is disrupted and the water molecule inserts between the OH and the aromatic ring. A second, extended anti conformer can also be detected.     

Influence of the second amino acid residue on the antidepressive activity of melanostatin analogs

It has been shown for melanostatin analogs that the energy of the HOMO, calculated by the CNDO/2 method for side substitutents of the second amino acid residue, is correlated with the antidepressive activity. The excessive electron density that appears in the peptide chain is delocalized on the MO of the substituent to which the AO of the first carbon atom makes the greatest contribution (LUMO).Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 29, No. 3, pp. 255–259, May–June, 1993.     

Study of the rotational isomerism of the side chain of 3,5-disubstituted hydantoins

The rotational isomerism of 3-alkyl(aryl)-5-alkyl(aralkyl)hydantoins in which the methylene group of the side chain, together with the methylidyne group in the 5 position of the ring, forms the structure of a substituted ethane was investigated by means of PMR spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 337–338, March, 1987.     

The structure of the xylan from cotton-plant stems

Summary The results of a study of the products of the hydrolysis and oxidative cleavage according to Barry of cotton-plant-stem xylan has shown that its main chain consists of 14--L-anhydroxylopyranose units. Each elementary link of the xylan contains 6–7 xylopyranose units and has two side chains formed by residues of D-glucose and D-glucuronic acid, which are attached in position 2 or 3 of the xylose units of the main chain.V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 305–308, May–June, 1973.     

An empirical correlation between structure and optical activity in a series of labdane diterpenoids

On the basis of the results of an analysis of the optical rotatory dispersion curves and a consideration of possible conformations of labdane diterpenoids, the conclusion has been drawn that labd-8(17)-ene derivatives with a 13E double bond or a voluminous substituent in the side chain do not obey Garman's additive scheme, and when there are no asymmetric centers in the side chain they have more negative values of the molecular optical rotation than is preducted by this scheme.Novosibirsk Institute of Organic Chemistry, Siberian Branch, Academy of Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 169–174, March–April, 1981.     

QCMS2 as a new method for providing insight into peptide fragmentation: The influence of the side‐chain and inter–side‐chain interactions

The identification of peptides and proteins from tandem mass spectra is a difficult task and multiple tools have been developed to aid this identification. We present a new method called quantum chemical mass spectrometry for materials science (QCMS²), which is based on quantum chemical calculations of bond orders, reaction, and transition‐state energies at the DFT/B3LYP/6‐311+G* level of theory. The method was used to describe the fragmentation pathways of five X‐His‐Ser tripeptides with X = Asn, Asp, Glu, Ser, and Trp, thereby focusing on the influence of the side chain and inter–side‐chain interactions on the fragmentation. The main features in the mass spectra of the five tripeptides were correctly reproduced, and a number of fragments were assigned to fragmentations involving the side chain and the influence of inter–side‐chain interactions. Product ion spectra were recorded to evaluate the capabilities and limitations of QCMS² and a number of conventional tools.     

Phenolic-iodine Redox Products: Mass Spectrometry,Thermal and Other Physico-chemical Methods of Analyses

Three interesting new compounds formed as a result of phenols-iodine redox reactions were investigated by mass spectral fragmentation (MS) and thermal analyses (TA) as well as some other physicochemical methods as microanalysis and infra-red spectroscopy to elucidate their structures. The characterization of the compounds was satisfactorily achieved by using the above analytical tools and their proposed general formulae, were found to be C₂₄H₁₅O₈I (PC-IO ₃ ^– ), C₂₄H₁₄O₁₂ I₂ (PG-IO ₃ ^– ) and C₁₂H₈O₆I₂ (PG-IO ₄ ^– ).The fragmentation pathways of PC-IO ₃ ^– , PG-IO ₃ ^– and PG-IO ₄ ^– have been examined using electron ionization (EI) mass spectrometry in comparison with thermal analyses (TG and DTA). Both decomposition modes were investigated, and the fragmentation pathways were suggested. The combined application of mass spectrometry and thermogravimetry (MS and TG) in the analysis of the products allowed the characterization of the fragmentation pathway in MS.The major pathway in both techniques of PC-IO ₃ ^– is due to the loss of CHO followed by CH₃I+2H₂O. It is due to the loss of 2H₂O followed by the loss of 2CH₃I for PG-IO ₃ ^– . While for PG-IO ₃ ^– it is related to the loss of 2H₂O followed by loss of 2CH₃I molecule stepwise. Different stabilities for initial products and some fragments are discussed.This revised version was published online in November 2005 with corrections to the Cover Date.     

Synthesis of new peptidic glycoclusters derived from β-alanine

The synthesis of an asymmetric glycocluster 1 has been achieved by coupling of a sugar unit with the β-alanine polypeptide, the principal chain, and combining a carbohydrate chain with the side chain causing it to branch from the N terminal. The synthesis of this side chain multivalent ligands is based on the scaffolding of some ω-amino acid (glycine, β-alanine, and GABA) derivatives. This method facilitated the synthesis of the cluster, of which the length of each unit differs.     

Mass-spectral behavior of 2-azatriptycene and its derivatives

The mass-spectral behavior of 11 aromatic and partially hydrogenated 2-azatriptycenes was investigated. It was established that the principal fragmentation pathway for these compounds is the formation of [M-nH] ⁺ and [M-nH]²⁺ ions (n = 1–6), as well as pseudoretrodiene fragmentation of the heterocyclic ring with the elimination of the atoms in the 2 and 3 positions.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1399–1402, October, 1981.     

Studies of 1-azabicyclo compounds

Furan and tetrahydrofuran amines with the amino group at position 4 or 5 in the side chain are intramolecularly dehydrated to the corresponding 1-azabicyclo compounds when passed over Al₂O₃-ZrO₂ catalyst at 325–330°.For Part III sec [1].