Shed plane leaves as a source ofα-tocopherol

A natural source of -tocopherol — shed plane leaves — has been found. The dynamics of the accumulation of a-tocopherol over the vegetation period of the plant has been studied, and a method has been developed for its isolation and quantitative determination.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. 3, pp. 372–374, May–June, 1995. Original article     

Unexpected observations during the total synthesis of calothrixin B–sodium methoxide as a source of hydride

During the total synthesis of calothrixin B, various novel and unexpected results were noticed such as cleavage of C–N bond in imine using sodium cyanoborohydride, sodium methoxide as a hydride source for reduction, deformylation in the presence of bromine, and deacylation using ceric ammonium nitrate (CAN). A detailed mechanism has been proposed for the unexpected results and a few of them are generalized. Temperature dependent NMR studies have been carried out for confirmation of the structure of one of the intermediates in the synthetic sequence.     

The role of tris-(α-thiopicolin anilide)-manganese(III) as a sensitiser in the photo-oxidative degradation of polyisobutylene

During the tris-(α-thiopicolin anilide)-manganese(III) (TPAM) sensitised photo-oxidative degradation of polyisobutylene (PIB) film, an initial rapid decrease of weight-average molecular weight has been observed by light scattering measurements. The degree of degradation, reaction rate, unsaturation and quantum yield of the chain scission are strongly increased by TPAM. UV and IR absorption spectra have been employed to substantiate a mechanism for the sensitisation process.     

The CF bond as a tool in the conformational control of amides

The conformation of 2-fluoro-N-(2-fluoroethyl)-propionamide 4 in the solid state indicates the influence of both a β-fluorine-amide gauche effect and an α-fluoroamide effect. The structure reveals the influence of two recently observed stereoelectronic effects associated with the CF bond, which has resulted in the successful prediction of the solid state conformation of amide 4. A gauche relationship (−69.9°) was observed for atoms N(1)C(4)C(5)F and a syn planar (2.0°) relationship was observed for N(1)C(3)C(2)F. The paper demonstrates the predictive power of using the CF bond as a tool in influencing the conformation of amides and peptides.     

The Application of Allyl as a Protecting Group in the Preparation Of Dinucleoside Carbonate

Inthepastseveralyears,antisenseoligonucleotidesandtheanalogueshavebeenproposedasanewclassofpharmaceuticals.Thetechnologyofantisenseisbasedontheantisensenucleotidesbindingtothetargetsequence(sensestrand)bybase-pairingtoinhibitgeneexpression'.Amajoradvantageofthestrategyisinthepotentialspecificityofaction.Theoretically,ifthenucleotidesequenceofthetargetmoleculeisknown,itispossibletowritedowndirectlythecorrespondentstructureofantisensestrand.However,inordertomakethisstrategysuccessful,theantisens…     

Heterometallic binuclear complexes involving the mercury—platinum bond as a source of a platinum carbenoid in reactions with fullerene-60

The cleavage of two σ-bonds and the formation of a metallocomplex, (η²-C₆₀)Pt(PPh₃)₂, occur in a new reaction between fullerene-60 and binuclear heterometallic compounds having a mercury-platinum bond (retro-insertion promoted by C₆₀). One of these,trans- Ph₂CHCH₂HgPt(PPh₃)₂Br,1, which contains an electron-donating group at the mercury atom, reacts two orders of magnitude faster thancis-(CF₃)₂CFHgPt(PPh₃)₂CH=CPh₂,2, which has an electron-withdrawing substituent at mercury. An asymmetrical organomercury compound is the second product of the reaction. The reactants and products have been characterized by spectroscopic data (¹H,³¹P NMR, UV-VIS) and elemental analyses. Compound 2, which is more stable to retro-insertion, gives a Pt-centered free radical upon photolysis. This was used for the free-radical functionalization of C₆₀. The platinumfullerenyl radicalcis-C₆₀Pt(PPh₃)₂R² was identified by EPR spectroscopy.     

The “One Source” cohort — evaluating the suitability of the human toenail as a manganese biomonitor

Numerous studies have demonstrated that the human toenail is a reliable biomonitor for the intake of Se and other elements. The objective of this study was to evaluate the use of the toenail as a biomonitor for Mn. Toenail specimens from One Source^™ multivitamin users and matched controls were selected. Se was measured using established NAA methods, then Mn was measured via a new procedure. The Se results confirmed the accurate classification of the cohort. However, the nail did not show significant, positive response to Mn supplementation. We hypothesize that the persistence of exogenous Mn confounded the results.     

The pH-dependence of preferential solvation as studied by intermolecular homo- and heteronuclear NOE measurements of adenosine in water–trifluoroethanol mixtures

A study of the state of solvation of the adenine ring in adenosine and adenosine 5-monophosphate disodium salt in water and in a (7.5:2.5) water–TFE mixture has been carried out by measurement of homo- and heteronuclear intermolecular NOE enhancements between water or TFE and the aromatic protons of these compounds. The results give evidence of site specificity in solute–solvent interaction for both solvent systems and preferential solvation of the solute by TFE in the water–TFE mixture. Significant pH dependence of these interactions has been discovered.     

Evaluating the biochemical potential for Irbid’s food waste as a source for energy

Solid waste generated from the city of Irbid is all directed to a local unlined landfill with no gas collection system. More than half of the waste stream is made of food waste which turns the landfill to a concentrated point source of greenhouse gases. To assess the impact that the landfill has at the moment on global warming and to evaluate the future value of the city’s waste as a source of biogas, 20 trucks of municipal solid waste were sampled. In addition, food waste samples from Irbid were collected from five different sources for 12 weeks to quantify their generation rates and to measure their components and chemical composition. Irbid’s solid waste was found to have a distinctively high biodegradable content 68%, which is typical of developing countries’ solid waste. Physical assessment showed that 38%, 6%, 33% and 23% of the food waste was rice, meat, fruits and vegetables, and bread, respectively. Measured methane yields for the volatile solids (VS) in rice, meat, fruits and vegetables, and bread were 362, 499, 352 and 375 mL/g VS, respectively. A representative food waste sample was created to test the actual methane yield and compare it to calculated one. Actual methane yield (414 mL/g VS) was greater than the calculated value (370 mL/g VS) based on food type proportions and their specific methane yield. To assess the anaerobic biodegradability of food waste, a stoichiometric calculation of the methane production was made based on the elemental analysis of all food waste elements. Food waste was found to have the chemical formula C₇H₁₆O₅N and calculated methane potential of 447 mL/g VS; indicating 85% anaerobic biodegradability of food waste, which makes Irbid’s waste perceived as a valuable source of energy.     

The total π-electron energy as a problem of moments: application of the Backus–Gilbert method

The total π-electron energy problem can be formulated as a classical problem of moments. This observation allows us to apply general methodologies developed in the field of moment’s theory to solve the total π-electron energy problem. In the present article, we apply the Backus–Gilbert method to obtain analytical expressions for the total π-electron energy in terms of its spectral moments.AMS subject classification: 30E05, 05C50, 92E10, 78M05     

The Future of Gas to Liquids as a Gas Monetisation Option

The paper introduces gas to liquids (GTL) as a monetising option from a technology, marketingand project perspective. GTL is complementary to LNG and pipelines. At the same time, using naturalgas as a source for fuels in the form of GTL helps countries around the world to diversify their energysupplies. Furthermore, gas-based products are inherently cleaner than oil products. Shell‘s proprietary GTL technology or SMDS (Shell Middle Distillates Synthesis), is discussed in some detail. The paperalso covers the challenges for successful implementation of GTL projects and why Shell is well positionedto take a lead in the industry on the basis of its long standing and broad experience in GTL research,plant operations, marketing and excellent track record in mega projects in the last thirty years. Shell‘scommitment to GTL is best demonstrated by the recent signing of a Heads of Agreement with Qatar Petroleum for the construction of the world‘s largest GTL plant. A key success factor is Shell‘s experiencewith marketing quantities of high quality GTL products from its 12,500 barrels per day plant at Bintulu,Malaysia since 1993. Further marketing opportunities will arise when new GTL capacity comes on-streamin the middle east when more quantities will become available to bulk users. Amongst the most interesting market will be automotive transportation, where clean GTL fuels can be positioned as an ‘alternativefuel beyond oil‘ providing energy security to host countries. Shell is actively engaging with a numberof regulators, automotive companies and governments worldwide including China, to demonstrate theperformance of GTL and its cost effectiveness in reducing local emissions. An added benefit is that GTLcan use existing infrastructure and requires no investment. Finally, the paper briefly discusses the coal toliquids (CTL) process as an alternative route to produce high quality GTL products and the key issuesrelating to the process.     

β-Cyclodextrin as a mimetic of the natural GFP-chromophore environment

The green fluorescent protein (GFP) chromophore has been anchored to β-cyclodextrin (βCD) via a copper(I)-catalyzed azide-alkyne cycloaddition. The photophysical properties of this new GFP-CD derivative have been evaluated, showing the formation of a self-inclusion complex and enhancement of fluorescence of the GFP-chromophore covalently bound to the βCD. This enhancement of fluorescence by encapsulation and hence fixation of the chromophore in a binding pocket mimics the effect exerted by the natural protein environment.     

The Synthesis of a γ-Keto-α-amino Acid,a Key Intermediate in the Synthesis of Monatin,a New Natural Sweetener

An efficient method was developed for the synthesis of the ketoamino acid 2, a key intermediate in the synthesis of the novel sweet compound, monatin 1. Preparation of 2 entails coupling of a suitably protected indole acetate anion to an aspartic acid derivative.     

α-Sulfur crystals as a visible-light-active photocatalyst

We show that in contrast to conventional compound photocatalysts, α-sulfur crystals of cyclooctasulfur (S(8)) are a visible-light-active elemental photocatalyst. The α-S crystals were found to have the ability not only to generate ·OH radicals but also to split water in a photoelectrochemical process under both UV-vis and visible-light irradiation. Although the absolute activity obtained was low because of the large particle size and poor hydrophilicity of the α-S crystals studied, there is great potential for increasing the activity with the assistance of known strategies such as surface modification, nanoscaling, doping, and coupling with other photocatalysts.     

Adsorption-Induced Segregation as a Method for the Target-Oriented Modification of the Surface of a Bimetallic Pd–Ag Catalyst

The effect of palladium segregation was studied which resulted from the effect of CO and O₂ on the surface structure and catalytic characteristics of the Pd–Ag₂/Al₂O₃ catalyst. The IR-spectroscopic study of adsorbed CO showed that Pd₁ centers isolated from each other by silver atoms predominated on the surface of reduced Pd–Ag₂/Al₂O₃, as evidenced by the almost complete absence of absorption bands typical for the multicentred CO adsorption. In the course of catalyst treatment with CO and O₂, the intensity of absorption bands characteristic of the multicenter CO adsorption considerably increased due to the transformation of a portion of monatomic Pd₁ centers into multiatomic Pd_n ones as a result of the surface segregation of Pd. In this case, a substantial increase in the catalyst activity in the liquid-phase hydrogenation of diphenylacetylene was observed. It was established that, after treatment with CO, the catalyst selectivity for the formation of a target olefin (stilbene) remained almost constant, whereas the treatment with O₂ led to a decrease in the selectivity because of more considerable surface modification.     

α-Picolinic acid as a colorimetric reagent: Determination of ferrous ion

α-Picolinic acid has been used as a reagent for the colorimetric estimation of ferrous ion. The transmittancy measurements show that iron from 0.08 p.p.m. to 12 p.p.m. may be easily determined with a cell of capacity 16 ml and thickness 20 mm. The effect of time, temperature and of diverse ions on the coloured system with an absorption maximum at 440 mμ have been critically examined. The optimum range with minimum relative error is found to be in the region of 1.6 to 8 p.p.m.By job's method the composition of the ferrous complex, which is highly soluble and stable in water, is Fe(C₆H₄O₂N)₂ with a dissociation constant in the order of 10^-5.α-Picolinsäure wurde als Reagens zur kolorimetrischen Bestimmung von Ferroionen benutzt. Mit dieser Methode kann man leicht Eisen in einer Konzentration von 0.08-12‰ in einer Zelle mit einem Fassungsvermögen von 16 ml und einer Dicke von 20 mm bestimmen. Der Einfluss der Zeit, der Temperatur und verschiedener anderer Ionen auf das gefärbte System mit einem Absorptionsmaximum bei 440 mμ wurde kritisch überprüft. Der optimale Bereich mit dem geringsten relativen Fehler wurde in dem Gebiet von 1.6-8‰ gefunden.Die Zusammensetzung des Ferrokomplcxes, der ausserordentlich gut löslich und stabil in Wasser ist, ist nach der Job'schen Methode Fe(C₆H₄0₂N)₂ und besitzt eine Dissoziationskonstante in der Grössenordnung von 10^-5.     

Ceramide formation on the γ-irradiation of galactocerebroside as a constituent of micelles

The radiation-initiated transformations of galactocerebroside (GalCer) as a constituent of micelles were studied. The radiation-chemical yields of decomposition of the starting substrate and formation of degradation products suggested that the formation of ceramide is the main process in the γ-radiolysis of GalCer. The irradiation of GalCer in the presence of dimethyl sulfoxide, which is an active scavenger of OH radicals, decreased the yield of ceramide. Ceramide was formed as a result of GalCer degradation with O-glycoside bond cleavage in the polar moiety of the lipid.     

Resolution of sclareolide as a key intermediate for the synthesis of Ambrox®

Sclareolide was efficiently resolved by a diastereomeric salt formation method using homochiral erythro-2-amino-1,2-diphenylethanol (ADPE) as a resolving agent.     

α-Phosphoryl Cyclopentanones as Possible Intermediates in the Total Synthesis of Sarkomycin

Abstract

In an effort to synthesize sarkomycin 1 trans-2-diphenylphosphinoyl-3-tris (methylthio) methyl-cyclopentanone 7 and trans-2-diphenylphosphinoyl-3-carbo-methoxy-cyclopentanone 8 were prepared. The Horner-Wittig reaction of the latter with formaldehyde failed. (±)-Sarkonycin 1 was prepared by a sequence of reactions starting from diethyl 2-oxopropanephosphonate. The key steps in this synthesis involve the intramolecular carbenoid cyclization of 1-diazo-2-oxopropanephosphonate 10 and the Horner-Wittig reaction of 2-diethoxyphosphoryl-3-carboxy-cyclopentanone 12 with formaldehyde.