The effect of stereochemical peculiarities on the electron-impact-induced fragmentation of matridine and its stereoisomers

With the aid of the mass spectra of 14,14-d₂ analogues the majority of the m/e 98 ions in the spectrum of allomatridine were shown to contain ring D, whereas in the case of matridine and isosophoridan the m/e 98 ions mainly include rings A or B. The m/e 84 ion results mostly from a charge localisation on ring D for allomatridine and isosophoridan, while in the case of matridine it may arise due to charge localisation on ring D accompanied by migration of the 14-H atom from the charged fragment, as well as on rings A or B with a hydrogen atom migrating to the charged species.     

Unexpected results from the re-investigation of the Beckmann rearrangement of ketoximes into amides by using TsCl

TsCl (p-toluenesulfonyl chloride), a commercially available organosulfonyl chloride, has been widely used as a stoichiometric dehydrogenation reagent in the transformation of ketoximes into corresponding amides via the Beckmann rearrangement. It has been now found to catalyze the Beckmann rearrangement with high catalytic efficiency, converting a wide range of ketoximes into their corresponding amides under mild condition with good to excellent yields (up to 99% of yield with 1-5 mol % of catalyst loading).     

Biosynthesis of the alkaloids ofAnabasis aphylla

The dynamics of the accumulation of free amino acids and the main alkaloids have been determined, and 15 free amino acids have been detected and identified, 11 having been determined quantitatively. The amounts of the main alkaloids have also been determined. An interrelationship of the amino acid lysine with the alkaloids has been shown. The interconversion of pachycarpine into aphylline and aphyllidine with the formation of a lactam group has been demonstrated experimentally.V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 56–60, January–February, 1980.     

Integral intensities of the absorption bands of the skeletal vibrations of the heteroaromatic ring in the IR spectra of the furanoquinoline alkaloids

1. The integral intensities of the bands of the skeletal vibrations of the heteroaromatic ring in the 1480–1630-cm⁻¹ region of eight furanoquinoline alkaloids have been measured. 2. A connection has been found between the values of ΣA and the structures of the furanoquinoline alkaloids and their derivatives which enables such a series of heteroaromatic compounds to be identified: It has been shown that the introduction of an -OCH₃ group into the γ position of the pyridine nucleus leads to a marked rise (almost twofold) in the value of ΣA;     

The roles of aldehyde dehydrogenases (ALDHs) in the PDH bypass of Arabidopsis

Background  

Eukaryotic aldehyde dehydrogenases (ALDHs, EC 1.2.1), which oxidize aldehydes into carboxylic acids, have been classified into more than 20 families. In mammals, Family 2 ALDHs detoxify acetaldehyde. It has been hypothesized that plant Family 2 ALDHs oxidize acetaldehyde generated via ethanolic fermentation, producing acetate for acetyl-CoA biosynthesis via acetyl-CoA synthetase (ACS), similar to the yeast pathway termed the "pyruvate dehydrogenase (PDH) bypass". Evidence for this pathway in plants has been obtained from pollen.     

Electrophoretic investigation of the seed proteins of the cotton plantGossypium hirsutum

The proteins of the buffer-soluble fraction of the seeds of cotton plants of the speciesGossypium hirsutum, wild and ruderal varieties, have been investigated by electrophoresis in polyacrylamide gel and have been subdivided into two classes. Characteristic components have been detected in the protein spectra of these samples. In diploid species of the cotton plant, in addition to characteristic protein components, individual components are also observed.Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 736–738, September–October, 1995. Original article submitted November 21, 1994.     

Studies of the solvent extraction of indium oxinate

An investigation of the extraction of radio-labelled 2.10^-5M indium from various aqueous solutions into a number of organic solvents containing oxine has been carried out. The effects of pH value, oxine concentration, masking agents, different organic phases, and temperature have been studied. Extraction constants and pH values of 50% extraction have been measured and compared with theoretically-calculatud values.     

A new kinetic approach to the fermentation of multisubstrate complex media

Ethanol production from natural complex media has been studied in this work. A new kinetic approach is presented for two-substrate media, such as hardwood hemicellulose hydrolysate, which predominantly consists of a mixture of xylose and glucose. It has been founded on the supposition that the whole ethanol production and biomass growth can be subdivided into two separated components imputable to glucose and xylose consumptions, respectively. A model describing the continuous fermentation in CSTR byPachysolen tannophilus has been also presented, and experimentally verified; it takes into account the different substrate consumption rates of these sugars contained in both natural and synthetic complex media.     

A computational study of the Dougherty model for the prediction of high-spin states in organic chemistry

The model proposed by Dougherty for the design of high-spin organic systems has been studied from a quantitative point of view using a Heisenberg Hamiltonian formalism. This analysis leads to a decomposition of the phenomenological coupling parameter, J, into contributions from individual active orbital sites and a decomposition of the spin multiplicity into terms from the ferromagnetic coupling unit and the spin-containing units. An analysis of the origin of quintet stability has been carried out for four molecular systems with quintet ground states that have previously been synthesized by Dougherty and by Adam. The results indicate that the ferromagnetic coupling unit plays the dominant role in determining high-spin stability as suggested by Dougherty and gives some insights that may be useful in the rational design of high-spin systems. Received: 31 July 1998 / Accepted: 21 September 1998 / Published online: 23 February 1999     

The azo coupling of 1-aryl quaternary salts of lepidine and quinaldine and some properties of the reaction products

A series of formazans has been obtained by the coupling of 1-aryllepidinium and 1-arylquinaldinium salts with diazonium salts. The formazans have been converted by oxidation into tetrazolium salts and by the action of acids into benzotriazines. The absorption spectra in the visible region have been measured in neutral, alkaline, and acid media.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 8, pp. 1104–1111, August, 1970.     

Composition of the neutral fraction from the oleoresin ofPinus sibirica

Conclusions 1. From the neutral fraction of the oleoresin ofPinus sibirica R. Mayr have been isolated new macrocyclic diterpene compounds-isocembrene (I) and isocembrol (VI).2. It has been shown that isocembrol is readily dehydrated into cembrene and isocembrene.Khimiya Prirodnykh Soedinenii, Vol. 5, No. 1, pp. 10–14, 1969     

Silicon-titanium xerogels: Synthesis and application to the determination of ascorbic acid and polyphenoles

Titanium and silicon-titanium xerogels have been obtained and it has been demonstrated that titanium(IV) incorporated into the xerogel matrix can participate in complexation reactions with ascorbic, gallic, ferulic, and caffeic acids and also rutin, quercetin, and dihydroquercetin present in aqueous solutions. In the case of dihydroquercetin 1 min of contact has been sufficient for achieving the equilibrium; the other compounds required 7–10 min. The stability constants of titanium(IV) complexes incorporated into xerogels reduced in the order dihydroquercetin > gallic acid > ascorbic acid > quercetin > caffeic acid > rutin. The procedures have been developed for solid-phase spectrophotometric determination of ascorbic, gallic, ferulic, caffeic acid as well as rutin, quercetin, and dihydroquercetin. The accuracy of the procedure has been examined by the standard addition method. The procedures for the determination of dihydroquercetin and ascorbic acid have been applied to the analysis of pharmaceutical preparations.     

Influence of the electrolyte composition of the subphase on the structure of 2D films of fullerene C60

The morphology of 2D films of fullerene C₆₀ on interfaces has been studied by Brewster angle microscopy and atomic force microscopy. Fullerene C₆₀ tends to aggregate, forming supramolecular structures with a surface area per C₆₀ molecule from 21.6 to 2900 Ų. As the area per C₆₀ molecule decreases, monomolecular clusters gradually transform into multiplayer structures. The introduction of an electrolyte into the system prevents the formation of fullerene globules and favors the formation of more homogeneous films.     

Extractive radiometric procedure for the estimation of fluoride

A radiochemical method for the determination of fluoride has been developed. The effect of fluoride on the extraction of the Fe/III/ thiocyanate complex into TBP in nitrobenzene has been utilized. Microgram quantities of F^– have been determined. Effect of diverse ions has also been reported. The method is applied for the determination of F^– in a natural sample of apetite.     

Ab initio investigation of the Young's modulus of polyamide‐6

The Young's modulus of the α form of polyamide‐6 has been calculated using the supermolecule model. The crystalline polymer was represented by a single‐chain molecule, divided into a head, body, and tail part. The body of the model contains an even number of polyamide‐6 units (4–16 units) and is representative for a polyamide‐6 chain. The periodicity of the system was not explicitly taken into account, but in a few tests the effect of a linear constraint has been evaluated. An n‐butyl and n‐pentyl group have been used as head and tail, respectively. In a number of additional calculations the length of the head and tail has been varied. For all supermolecule models the equilibrium and elongated structures have been optimized using ab initio Hartree–Fock calculations with a 6‐31G** basis set. From the energy values of the optimized structure a Young's modulus of 334 GPa has been extrapolated for both the unconstrained and linearly constrained models. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2003     

Investigations in the fie ld of substituted furanurona ldehydes steric directivity of the nitromethane condensation

Summary 1. The condensation of the anomeric methyl 2,3-di-O-benzyl-D-xylofuranosiduronaldehydes with nitromethane has been studied.2. It has been shown that the position of the substituent at the glycosidic center has an influence on the steric directivity of this reaction.3. The structure of the 6-nitro-6-deoxyhexofuranosides synthesized has been confirmed by their conversion into known derivatives of methyl D-glucofuranosides.Translated from Khimiya Prirodnykh Soedinenii, No. 1, pp. 8–12, January–February, 1972.     

A quantum chemical calculation on Fe(CO)5 revealing the operation of the Dewar–Chatt–Duncanson model

A nonstandard computational scheme has been applied to calculate Fe(CO)₅ with the aim to illustrate the operation of the Dewar–Chatt–Duncanson model by computation. A full configuration interaction (CI) calculation in an active space has been performed. The active space is built from naturally localized molecular orbitals (NLMOs) localized in bond regions or forming lone pairs. For selecting this active space, Weinhold's perturbation theory formulated in the natural bond orbital (NBO) space has been applied. Bonding, lone pair, and antibond NBOs exhibiting large interaction energies serve to define the active space. The actually applied active space, however, comprises NLMOs that are close in shape to the NBOs indicated by perturbation theory. Thus, a CI calculation with localized orbitals has been performed meeting the classical reasoning of chemists that is often based on local bonding concepts. The computational scheme yields the Lewis structure for Fe(CO)₅ whose energy is identical to the Hartree–Fock energy. The Lewis energy comprises CO → Fe σ‐electron transfer (ET) and CO ← Fe electron back donation (BD). This Lewis energy gets lowered by localized correlation energy contributions caused by ET processes where electrons are back donated from the Fe d‐lone pairs into the CO ligands. Thus, electron correlation within the selected active space is dominated by electron BD. Energies and electron populations of the NBOs support the notion that electrons are preferentially back donated into the equatorial CO ligands. Weights of local Slater determinants, determining the correlation energy, also point to a predominant BD into the equatorial CO ligands. Correlation energy increments resulting from electron BD into single antibond orbitals of the CO ligands have been calculated. These energy quantities also demonstrate that BD into the equatorial CO ligands is more energy lowering than BD into the axial CO ligands. © 2012 Wiley Periodicals, Inc.     

On the modification of the nitrile groups of acrylonitrile/butadiene/styrene into oxazoline in the melt

Oxazoline functionality is well known to be highly reactive toward a lot of other functional groups like carboxyls, hydroxyls, mercaptans, and amines. In this work we report the possibility to modify the nitrile groups of an acrylonitrile/butadiene/styrene (ABS) copolymer into oxazoline in the molten state in the presence of aminoethanol as modifier agent and zinc acetate as a catalyst. The reaction has been carried out in a batch mixer and in a corotating twin screw extruder. The conversion of the nitrile groups into oxazoline has been verified by infrared spectroscopy, NMR analysis microanalysis and confirmed by thermomechanical characterization. The results indicate that the kinetic of grafting is fast and the conversion of the nitrile groups into oxazoline relatively high, encouraging the use of this modified polymer in the reactive compatibilization of ABS‐based blends. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 1795–1802, 2000     

The biosynthesis of the alkaloids of croton sparsiflorus morong

Incorporation of tyrosine, dopa, dopamine, 4-hydroxyphenylpyruvic acid, (±)-, norcoclaurine-1-carboxylic acid, -norcoclaurine, -coclaurine, and -N-methylcoclaurine into N-methylcrotsparine, N-methylcrotsparinine and N-methylsparsiflorine in Croton sparsiflorus Morong has been studied. The evidence supports the direct oxidative coupling of (+)-, and (-)-N-methylcoclaurines to give N-methylcrotsparine and N-methylcrotsparinine respectively. Tracer experiment show that N-methylcrotsparine undergoes dienone-phenol rearrangement to give N-methylsparsiflorine. A double labelling experiment with (±)-N[¹⁴C]methyl[1-³H]coclaurine demonstrated that the H atom at the asymmetric centre in the 1-benzylisoquinoline precursor is retained in the bioconversion. The intermediacy of norcoclaurine-1-carboxylic acid and specific incorporation of dehydro-N-methylcoclaurinium salt into the bases have been demonstrated.     

Sodium iodide/boron trifluoride etherate: A mild reagent system for the conversion of allylic and benzylic alcohols into corresponding iodides and sulfoxides into sulfides

A variety of allylic and benzylic alcohols have been converted into the corresponding iodides using NaI/BF₃.Et₂O. Selective conversion of allylic and benzylic alcohols in preference to primary saturated alcohols has also been demonstrated. Further, the same reagent system has been used to convert sulfoxides into sulfides under mild conditions.