Showing papers in "Journal of The Chemical Society-perkin Transactions 1 in 1972"
TL;DR: In this paper, the isolation and determination of structure of some plant procyanidins in their free phenolic forms are described, and the distribution of procyclanidin in the tissues of twentynine plant species has been examined and the biogenetic implications of this study are briefly discussed.
Abstract: The isolation and determination of structure of some plant procyanidins in their free phenolic forms are described. The distribution of procyanidins in the tissues of twenty-nine plant species has been examined and the biogenetic implications of this study are briefly discussed.
380 citations
TL;DR: A series of alcohols and amines have been oxidised at oxide-covered nickel, silver, copper, and cobalt anodes in aqueous alkaline solutions as mentioned in this paper, and it was shown that the mechanism of these oxidations involves hydrogen abstraction from the substrate by an oxide species rather than direct electron transfer to the anode.
Abstract: A series of alcohols and amines have been oxidised at oxide-covered nickel, silver, copper, and cobalt anodes in aqueous alkaline solutions. The kinetics of these electrode processes have been studied and it is shown that the mechanism of these oxidations involves hydrogen abstraction from the substrate by an oxide species rather than direct electron transfer to the anode. The mechanism put forward is compared with those commonly suggested for the chemical reactions of transition-metal oxides and for heterogeneous catalysis.
313 citations
TL;DR: The linked-atom least-squares approach is a logical and convenient procedure for achieving the necessary synthesis of different types of data as discussed by the authors, which has been used extensively in analysing polynucleotides and polypeptides but not, so far, polysaccharides.
Abstract: X-Ray diffraction data from polymers are, by themselves, rarely sufficient to allow determination of atomic positions within a few tenths of an Angstrom. When this accuracy is required, the polymer diffraction data have to be supplemented by stereochemical data from accurate analyses of relevant monomers. The linked-atom least-squares approach is a logical and convenient procedure for achieving the necessary synthesis of different types of data. The procedure has been used extensively in analysing polynucleotides and polypeptides but not, so far, polysaccharides. Its adaptation for these is described, with particular attention being paid to the precise conformations of rings that dominate the geometry of these polymers.Since the determination of accurate structures of polysaccharides depends both on diffraction data from the polymers themselves and on additional data such as bond-lengths and bond-angles, we present a survey of the values of these latter quantities as determined by X-ray diffraction analysis of single crystals of appropriate small molecules.As examples of the application of linked-atom least-squares methods we present and discuss the preparation of standard α- and β-D-glucose rings and preliminary molecular models of chitin and ι-carrageenan.
189 citations
TL;DR: In this article, the carboxy-group of a series of substituted N-methylmaleamic acids is shown to be remarkably sensitive to the pattern of substitution on the carbon-carbon double bond.
Abstract: The efficiency of intramolecular catalysis of amide hydrolysis by the carboxy-group of a series of substituted N-methylmaleamic acids is remarkably sensitive to the pattern of substitution on the carbon–carbon double bond. A single alkyl group increases the rate of hydrolysis by a factor which increases with its size. A second alkyl substituent has a disproportionately larger effect, which is sharply reduced when the two groups are joined together in a ring. The rates of hydrolysis of a series of dialkyl-N-methylmaleamic acids range over more than ten powers of ten, and the ‘effective concentration’ of the carboxy-group of the most reactive compound studied is greater than 1010M. This amide, dimethyl-N-n-propylmaleamic acid, is converted into the more stable dimethylmaleic anhydride with a half-life of less than 1s at 39 °C below pH 3. The mechanism of catalysis, and the factors responsible for this extremely high reactivity, are discussed.
154 citations
TL;DR: In this article, the 13C resonances of the glycerol and choline groups of dipalmitoyl-lecithin in CD3OD, CDCl3, and D2O have been assigned from the 14N−13C and 31P-13C coupling constants, and proton decoupling studies on the assigned 1H spectra.
Abstract: The 13C resonances of the glycerol and choline groups of dipalmitoyl-lecithin in CD3OD, CDCl3, and D2O have been assigned from the 14N–13C and 31P–13C coupling constants, and proton decoupling studies on the assigned 1H spectra. Well-defined solvent effects are observed, but the chemical shifts for dipalmitoyl-lecithin in bilayers in D2O are very similar to the shifts of the corresponding resonances in biological membranes. From an analysis of the 1H spectrum of the CH2 multiplet in the CH–CH2OCOR fragment, the two vicinal coupling constants were extracted and used to calculate rotamer populations from a Karplus treatment. In a high proportion of the molecules of dipalmitoyl-lecithin in CD3OD and in CDCl3 the fatty acid chains are arranged gauche to each other, suggesting the presence of strong hydrophobic interactions. From an AA′BB′ analysis of the choline –CH2·CH2–fragment in dipalmitoyl-lecithin observed vicinal coupling constants indicate a similar conformation to that found in choline derivatives where an electrostatic interaction between the N+ and the O atoms leads to the conformation being exclusively in the gauche+N/O form.
117 citations
TL;DR: In this article, a number of new 22 π-electron macrocycles containing pyrrole, furan, and thiophen rings and one or two direct links are described.
Abstract: Rational syntheses are described of a number of new 22 π-electron macrocycles containing pyrrole, furan, and thiophen rings and one or two direct links. A further example of the sulphur extrusion process applied to macrocycle synthesis is provided. N.m.r. studies are used to show that all the macrocycles are aromatic, and they all contain intense Soret type bands in their visible spectra. The dioxasapphyrin does not form metal complexes and shows remarkable rate differences in the electrophilic deuteriation of the meso-positions.
117 citations
TL;DR: Potassium iodide has been determined by the heavy-atom method and refined by full-matrix least-squares to a final R of 0·09 on 1603 diffractometer data.
Abstract: Potassium iodide forms a 1 : 2 complex with the cyclic polyether ‘benzo-15-crown-5’. The crystals are tetragonal with a=b= 17·84(1), c= 9·750(6)A, Z= 4, space group P4/n. The crystal structure has been determined by the heavy-atom method and refined by full-matrix least-squares to a final R of 0·09 on 1603 diffractometer data. The complex cation has crystallographic symmetry , the potassium being ‘sandwiched’ between two centro-symmetrically related ligand molecules. In each of these the five ether-oxygen atoms are approximately coplanar, the cation lying 1·67 A away from this plane, so that the ten-co-ordination is an irregular pentagonal antiprism. The K–O distances range from 2·777(7) to 2·955(8)A. Iodide ions occupy two sets of positions with 4 or symmetry and the arrangement of complex cations and anions resembles the caesium chloride structure; there is no interaction between the anions and the metal.
90 citations
TL;DR: Aeroplysinin-1, an antibacterial bromo-compound from the sponge Verongia aerophoba, is the first example of a naturally occurring 1,2-dihydroarene-1-2-Diol.
Abstract: Aeroplysinin-1, an antibacterial bromo-compound from the sponge Verongia aerophoba, is the first example of a naturally occurring 1,2-dihydroarene-1,2-diol.
88 citations
TL;DR: The trail pheromone of Nasutitermes is shown to be the cembrene analogue 12-isopropyl-1,5,9-trimethylcyclo-tetradeca-1.5, 9-triene (10) by degradation, by comparison of its perhydro-derivative with per-hydrocembrene, and by isomerisation with sodium methylsulphinylmethanide followed by degradation as discussed by the authors.
Abstract: The trail pheromone of Nasutitermes is shown to be the cembrene analogue 12-isopropyl-1,5,9-trimethylcyclo-tetradeca-1,5,9-triene (10) by degradation, by comparison of its perhydro-derivative with perhydrocembrene, and by isomerisation with sodium methylsulphinylmethanide followed by degradation. The configurations of the double bonds are at present unknown. A key aspect of the work is the use of a quantitative micro-ozonolysis procedure.
83 citations
TL;DR: In this paper, four new compounds have been isolated from the heartwood of Combretum molle and have been shown both by chemical and spectroscopic methods and by synthesis to be 4,7dihydroxy-2,3,6-trimethoxyphenanthrene, 4,6,7-trihydroxy- 2,3-dimethoxy- and 2,6dihdroxy-3,4,7,trimethylhexylhexoxy-9,10-diphreeysanthrene.
Abstract: Four new compounds have been isolated from the heartwood of Combretum molle and have been shown both by chemical and spectroscopic methods and by synthesis to be 4,7-dihydroxy-2,3,6-trimethoxyphenanthrene, 4,6,7-trihydroxy-2,3-dimethoxy- and 2,6-dihydroxy-3,4,7-trimethoxy-9,10-dihydrophenanthrene, and 3,4′-dihydroxy-4,5-dimethoxybibenzyl. The relevance of the latter compound to the biogenesis of the phenanthrenes and 9,10-dihydrophenanthrenes is discussed. The phenol (C′) from Combretum apiculatum has now been unambiguously established by total synthesis to be 6,7-dihydroxy-2,3,4-trimethoxyphenanthrene.
72 citations
TL;DR: In this paper, the homologous spirocyclohexadienylisoxazoles (XIII and XIV) and homoaerothionin (XIV) compounds from the sponges V. thiona and V. aerophoba are shown to be the homology of homoerothions.
Abstract: Aerothionin and homoaerothionin, tetrabromo-compounds from the sponges V. thiona and V. aerophoba are shown to be the homologous spirocyclohexadienylisoxazoles (XIII) and (XIV), respectively.
TL;DR: In this article, the crystal structures of the title compounds have been determined from X-ray diffractometer observations, and the structure was solved by the iterative application of Sayres' equation, and refined by least-squares methods to R 0·056 for 1414 independent observations.
Abstract: The crystal structures of the title compounds have been determined from X-ray diffractometer observations. The molecules of the cyclic ether are centrosymmetric with Z= 2 in a monoclinic unit cell having a= 16·960, b= 8·920, c= 9·096 A, β= 90·03°, and space group P21/c. They form loops approximately parallel to the a axis. The structure was solved by the iterative application of Sayres' equation, and refined by least-squares methods to R 0·056 for 1414 independent observations.In the complex Z= 4 in an orthorhombic unit cell having a= 19·576, b= 12·405, and c= 12·965 A with space group Pnna. The structure was solved by conventional Patterson and Fourier methods and refined by least-squares techniques to R 0·046 for 1102 independent observations. Each potassium ion lies on a two-fold axis, and is enclosed by a ligand molecule wrapped round to give ten K–O distances in the range 2·850(6)–2·931(6)A. The iodide ions also lie on two-fold axes and are not in contact with potassium. The packing of the complex cations and the iodide ions is a distorted sodium chloride structure.Bond lengths and angles in the complexed and free molecules are the same; the conformations and different. Four of the C–C–O–C angles change from trans in the free molecule to gauche in the complex; the remaining torsion angles are of the same type in both forms but corresponding ones differ by as much as 30° and the sign may be reversed.
TL;DR: In this article, a simple synthesis of dimethyl 3,10-dihydro-1,12-dhydroxy-4,5,8,9-tetramethoxy-3,10 -dioxoperylene-2,11-dicarboxylate (2), a key intermediate in the synthesis of the Elsinoe pigments, is described, and unusual mass spectrometric fragmentation of compound (2) and some related compounds, with loss of one oxygen atom, is discussed.
Abstract: A simple synthesis of dimethyl 3,10-dihydro-1,12-dihydroxy-4,5,8,9-tetramethoxy-3,10-dioxoperylene-2,11-dicarboxylate (2), a key intermediate in the synthesis of the Elsinoe pigments, is described, and the unusual mass spectrometric fragmentation of compound (2) and some related compounds, with loss of one oxygen atom, is discussed.
TL;DR: In this paper, the authors studied the reactions of the hydroxyl radical with a number of compounds containing the unit CHX-CHY, where X = OH or OMe and Y = OH, OAc, Halogen, or a protonated amino-group.
Abstract: The reactions of the hydroxyl radical with a number of compounds containing the unit –CHX–CHY–, where X = OH or OMe and Y = OH, OAc, Halogen, or a protonated amino-group, have been studied by e.s.r. spectroscopy. The transient species involved have been identified on the basis of their hyperfine splittings and g-factors; in the case of the radical ·CH(OH)·CH2NH3+ and its derivatives, clear trends in the proton and nitrogen nitrogen splittings are observed as the NH hydrogen atoms are successively replaced by methyl groups, and these have been rationalised in terms of an interaction involving both hydroxy- and amino-substituents.The data not only support the view that radicals containing the fragment –Ċ(OH)–C(OH)[graphic omitted] undergo acid-catalysed elimination of water but also reveal further details of this reaction and information about related heterolytic processes; for example, there is evidence that the radical cation MeOCH–ĊH2 is formed transiently from the radical ·CH(OMe)·CH2X (X = Cl or OAc). Amines do not appear to fragment heterolytically from radicals of the type ·CH(OH)·CH2NR3+, but the formation of the species Me3N·+ from the choline cation suggests that the C–N bond in the species ·CH(OH)·CH2NMe3+ readily undergoes homolysis.
TL;DR: The succinimidyl esters of mono-, di, tri, and tetra-γ-benzyl-D-glutamyl-L-leucine have been prepared from the corresponding acids by the dicyclohexylcarbodi-imide method, and the method is recommended as a procedure of choice for the synthesis of sequential polypeptides.
Abstract: The succinimidyl esters of mono-, di-, tri-, and tetra-γ-benzyl-D-glutamyl-L-leucine (VII; n= 1–4) have been prepared from the corresponding acids (V; n= 1–4), which were synthesised by the dicyclohexylcarbodi-imide method; the t-butoxycarbonyl group was used for amino-group protection and the 2-methylthioethyl ester group for carboxy-protection. Polymerisation of these esters gave satisfactory yields of the corresponding sequential polypeptides (I; n= 1–4) with molecular weights of between 11,000 and 31,000. Little racemisation (1–2%) accompanies the polymerisations, and the method is recommended as a procedure of choice for the synthesis of sequential polypeptides.
TL;DR: In this article, it is suggested that the latter reaction involves a non-aromatic meso-thia-macrocyclic intermediate which loses sulphur by a disrotatory cyclisation to a thiiran intermediate followed by cheletropic loss of sulphur.
Abstract: The preparation of 21,24-dioxacorroles by condensation of dipyrromethane-5,5′-dicarboxylic acids with 5,5′-diformyl-2,2′-bifuryl or bis-(5-formyl-2-furyl) sulphide is described. It is suggested that the latter reaction involves a non-aromatic meso-thia-macrocyclic intermediate which loses sulphur by a disrotatory cyclisation to a thiiran intermediate followed by cheletropic loss of sulphur. Some evidence for this proposal is provided by the preparation of meso-thiaphlorins and a study of their thermolyses to give corroles. Further examples of sulphur extrusion from a meso-dithiaphlorin, to give a meso-thiacorrole, are given and rate enhancements, in the sulphur extrusion process, which are observed in metal complexes are discussed. Some electrophilic deuteriation studies on the 21,24-dioxa-corroles are reported.
TL;DR: The action of hydrogen peroxide in pyridine on a variety of metal complexes of octa-ethylporphyrin under specified conditions has been shown to give metal octaethyloxophlorin derivatives in those cases where the complexed metal ion has a readily available higher oxidation level.
Abstract: The action of hydrogen peroxide in pyridine on a variety of metal complexes (Mn, Fe, Co, Ni, Cu, and Zn) of octa-ethylporphyrin under specified conditions has been shown to give metal octaethyloxophlorin derivatives in those cases where the complexed metal ion has a readily available higher oxidation level. Manganese(III) octaethyloxophlorin and dipyridinecobalt(III) octaethyloxophlorin prepared in this way have been characterised; they are identical with the products'of appropriate metallation of octaethyloxophlorin prepared by ring synthesis. Although iron(III) octaethyloxophlorin has not been isolated from the reaction, direct demetallation gives octaethyloxophlorin, and benzoylation followed by demetallation gives 5-benzoyloxyoctaethylporphyrin, again in each case identical with an authentic sample prepared by ring synthesis. Iron(III) octaethyloxophlorin readily undergoes autoxidation in pyridine to give, after hydrolysis, octaethylbilatriene-abc. The implications of these observations for the chemistry of haem catabolism are discussed.
TL;DR: Bromination of pyrene or 1-bromopyrene with limited amounts of bromine affords 1,6-dibromyrene and 1,8-di bromyric acid.
Abstract: Treatment of pyrene or 1-bromopyrene with limited amounts of bromine affords 1,6-dibromopyrene and 1,8-di-bromopyrene (not isolated pure by previous workers). Further bromination of either dibromide gives 1,3,6-tri-bromopyrene.
TL;DR: The principle of olefin synthesis by two-fold extrusion processes is enunciated in this article, and seven possible systems have been examined, the two most promising involving the extrusion of carbon dioxide and sulphur and of nitrogen and sulfur.
Abstract: The principle of olefin synthesis by two-fold extrusion processes is enunciated. Seven possible systems have been examined, the two most promising involving the extrusion of carbon dioxide and sulphur and of nitrogen and sulphur. A novel system containing azo and lactone functions afforded nitrogen, keten, and ketone instead of nitrogen, carbon dioxide, and olefin.
TL;DR: 5-Methylphenazinium-1-carboxylate has been synthesised and has been converted by aqueous ammonia and cultures of Ps.
Abstract: 5-Methylphenazinium-1-carboxylate has been synthesised. It has been converted by aqueous ammonia and cultures of Ps. aeruginosainto aeruginosin A.
TL;DR: In this paper, the results of homolytic acylation of compounds containing pyridine and pyrazine rings are reported, aldehydes being used as source of acyl radicals.
Abstract: The results of the homolytic acylation of compounds containing pyridine and pyrazine rings are reported, aldehydes being used as source of acyl radicals. The reactions proceed in high yields and with complete selectivity at positions α and γ to a heterocyclic nitrogen atom. The factors affecting mono- and poly-substitution and the formation of 9-acyl-9,10-dihydro-derivatives with acridine are discussed. A new process of homolytic acylation, based on decarboxylation of α-keto-acids, is also reported.
TL;DR: Azadirachtin (C35H44O16), isolated from the seeds of the Neem tree and found to be highly active in inhibiting the feeding response of the desert locust (Schistocerca gregaria), has been shown to be a highly oxygenated triterpenoid substance, with fourteen of the oxygen atoms deployed in five ester groups, three free hydroxy-groups and a dihydrofuran ring; the remaining oxygen atoms are tentatively assigned to two ether groups as discussed by the authors.
Abstract: Azadirachtin (C35H44O16), isolated from the seeds of the Neem tree (Azadirachta indica) and found to be highly active in inhibiting the feeding response of the desert locust (Schistocerca gregaria), has been shown to be a highly oxygenated triterpenoid substance, with fourteen of the oxygen atoms deployed in five ester groups, three free hydroxy-groups and a dihydrofuran ring; the remaining oxygen atoms are tentatively assigned to two ether groups.
TL;DR: In this article, the tetrahydro-derivative of the heptacyclotetradecane Binor-S in the gas phase in hydrogen chloride over a chlorinated platinum-alumina catalyst at 150° or in solution in dichloromethane containing alumin-ium chloride gives diamantane in high yields.
Abstract: Rearrangement of the tetrahydro-derivative of the heptacyclotetradecane Binor-S in the gas phase in hydrogen chloride over a chlorinated platinum-alumina catalyst at 150° or in solution in dichloromethane containing alumin-ium chloride gives diamantane in high yields. Methods for functionalisation of diamantane have been developed. Chlorination at 0° with alum'inium chloride–acetyl chloride yields equal amounts of 1- and 4-chlorodiamantane (the so-called zonal and apical derivatives) whereas use of chlorosulphonic acid at –5° yields mainly the 1-chloro-isomer. Hydrolysis of the chlorides yields the corresponding alcohols, which are separable by chromatography over alumina. The chlorides and alcohols can be equilibrated with aluminium chloride and with concentrated sulphuric acid, respectively. Oxidation of diamantane with 96% sulphuric acid at 75° yields diamantanone, 9-hydr-oxydiamantan-3-one, and diamantane-4,9-diol. Treatment of diamantan-3-ol with 70% sulphuric acid yields a mixture of mono-ols, 9-hydroxydiamantan-3-one, diamantane-3,9-diol, and diamantane-4,9-diol.
TL;DR: The crystal structure of the title complex determined from three-dimensional diffractometer data has been determined from 3D diffractometry data as mentioned in this paper, and the exact absolute configuration of the molecule is known.
Abstract: The crystal structure of the title complex determined from three-dimensional diffractometer data. Z= 4 in an orthorhambic unit cell having a= 12·271, b= 9·550, c= 15·719 A, and space group P212121. Full-matrix least-squares refinement based on 887 observations has led to R 0·048 for the correct absolute configuration of the molecule.The sodium ion is surrounded by a pentagonal pyramid of oxygen atoms. The base is formed by those of the cyclic ether with Na–O 2·35(1)–2·43(1)A and the sodium ion is 0·75 A from this plane towards the apical water molecule, Na–O 2·29(1)A. The iodide ion does not interact with the sodium ion but may form hydrogen bonds to water molecules [O⋯I 3·47(1) and 3·51(1)A], linking the complexes in chains along the b-axis of the crystal.
TL;DR: The electrical conductivity of hexacene hexasulphide is similar to that of the well-known naphthacene tetrasulphides as mentioned in this paper and 109 times greater than that of pentacene.
Abstract: Pentacene and hexacene both react with sulphur to form stable hexasulphides for which double fused thiathiophthen structures (6) and (8) or (9) are proposed. The electrical conductivity of hexacene hexasulphide is similar to that of the well-known naphthacene tetrasulphide (1) and 109 times greater than that of pentacene hexasulphide. Replacement of the sulphur in (1) by selenium gives a tetraselenide (14) of similar conductivity to (1). The new naphthaceno[5,6-cd][1,2]dithiole (10) is described.
TL;DR: In this article, 4-Azido-2,3,5,6,6-tetrafluoropyridine was shown to decompose into nitrogen and an intractable solid at temperatures above ca. 130 °C, undergoes the Staudinger reaction with tri-phenylphosphine at room temperature, reacts with dimethyl sulphoxide at elevated temperatures to give a sulphoximide, partakes in 1,3-dipolar cycloaddition reactions with benzyne, diphenylacetylene, phenylacetane,
Abstract: 4-Azido-2,3,5,6-tetrafluoropyridine can be prepared by nitrosation of 2,3,5,6-tetrafluoro-4-hydrazinopyridine or, preferably, treatment of pentafluoropyridine with sodium azide in acetonitrile, a reagent that converts 3-chloro-2,4,5,6-tetrafluoro- and 3,5-dichloro-2,4,6-trifluoro-pyridine into 4-azido-3-chloro-2,5,6-trifluoro- and 4-azido-3,5-dichloro-2,6-difluoro-pyridine, respectively. 4-Azido-2,3,5,6-tetrafluoropyridine decomposes smoothly into nitrogen and an intractable solid at temperatures above ca. 130 °C, undergoes the Staudinger reaction with tri-phenylphosphine at room temperature, reacts with dimethyl sulphoxide at elevated temperatures to give a sulphoximide, partakes in 1,3-dipolar cycloaddition reactions with benzyne, diphenylacetylene, phenylacetylene, cyclopentadiene dimer, and norbornene, yields 4-anilino-2,3,5,6-tetrafluoropyridine with benzene at 175 °C, and reacts with cyclohexane to give the C–H ‘insertion’ product 4-(cyclohexylamino)-2,3,5,6-tetrafluoropyridine and 4-amino-2,3,5,6-tetrafluoropyridine. Thermal decomposition of the azide in a mixture of cyclo-hexane, -heptane, and -octane reveals that C–H ‘insertion’ is encouraged by increase in ring size, and thermolysis experiments with cis- and trans-1,2-dimethylcyclohexane show that this type of reaction lacks stereospecificity. The results of reactions between the azide and trans-4-methylpent-2-ene at elevated temperatures indicate that 1,3-dipolar cycloaddition occurs before nitrene generation can be achieved. Authentic samples of the new amino-pyridines [PhNHpyF, cyclo-CnH2n–1·NHpyF(n= 6, 7, or 8), cis- and trans-cyclo-1,2-Me2C6H9·NHpyF, and cis- and trans-Pri[graphic omitted]pyF(pyF= 2,3,5,6-tetrafluoro-4-pyridyl)] encountered in this work can be obtained via nucleophilic attack by the appropriate amines on pentafluoropyridine.
TL;DR: Two rational syntheses of L-phenylalanine [(2S)-isomer] have been devised which allow labelling with isotopic hydrogen at C-3 in configurations established by chemical correlation with [2-2H1]succinic acid.
Abstract: Two rational syntheses of L-phenylalanine [(2S)-isomer] have been devised which allow labelling with isotopic hydrogen at C-3 in configurations established by chemical correlation with [2-2H1]succinic acid. The labelled samples have been used to prove that L-phenylalanine ammonia-lyase eliminates the 3-pro-S hydrogen atom of L-phenylalanine together with ammonia to give trans-cinnamic acid (a) with the isolated enzyme from potatoes and (b) during the biosynthesis of colchicine in intact Colchicum autumnale plants.The biochemical formation of the C6–C1 unit required for the construction of haemanthamine (30) in Amaryllidaceae plants involves loss of the hydrogen atom from C-3 of cinnamic acid.
TL;DR: Condensation reactions of o-halogenopyridine-carboxylic acids with carbanions in the presence of copper or copper salts have been investigated in this paper.
Abstract: Condensation reactions of o-halogenopyridinecarboxylic acids with carbanions in the presence of copper or copper salts have been investigated. For example, 2-bromopyridine-3-carboxylic acid reacted with acetylacetone and with ethyl acetoacetate to give 2-acetonylpyridine-3-carboxylic acid and ethyl 3-carboxy-2-pyridylacetate respectively. This bromo-acid condensed similarly with β-diketones and β-keto-esters, and with diethyl malonate, an acyl group being eliminated by ethanolysis in each case. 2-Substituted 1,3-dicarbonyl compounds did not react. Examples of such condensations have been obtained with three of the four possible o-halogeno-acid isomers of the pyridine series. 4-halogenopyridine-3-carboxylic acid being the exception. These products are useful intermediates in the synthesis of naphthyridine derivatives. Thus 2-acetonylpyridine-3-carboxylic acid condensed with ammonia to form 7-methyl-1,6-naphthyridin-5(6H)-one and with amines, hydroxylamine, and hydrazine to give corresponding 6-substituted compounds, but reaction with methylhydrazine yielded 2,5-dihydro-2,4-dimethylpyrido[3,2-d][1,2]diazepin-1-one.
TL;DR: In this article, the 31P and 13C n.m.r. spectra for some tertiary phosphines were examined and factors affecting the chemical shifts and coupling constants were examined.
Abstract: The 31P and 13C n.m.r. spectra for some tertiary phosphines are reported. Factors affecting the chemical shifts and coupling constants are examined, and it is suggested that the major factor involved in determining changes in chemical shifts from one tertiary phosphine to another is the bond angle at the nucleus concerned.
TL;DR: In this paper, 10 new compounds isolated from the heartwood of Combretum psidioides have been shown to be 7-hydroxy-2,4,6-trimethoxy-, 7hydroxy -2,3,4-6-tetramethoxy, 2,7-dihydroxy-3, 4,6, 6-trIMETHoxy-, and 2.6, 7-7-trihexyl-trihydroxyl-3-4-dimethoxy-phenanthrene, the 9,10
Abstract: Ten new compounds isolated from the heartwood of Combretum psidioides have been shown to be 7-hydroxy-2,4,6-trimethoxy-, 7-hydroxy-2,3,4,6-tetramethoxy-, 2,7-dihydroxy-3,4,6-trimethoxy-, and 2,6,7-trihydroxy-3,4-dimethoxy-phenanthrene, the 9,10-dihydro-derivatives of these four compounds, and 4′-hydroxy-3,4,5-trimethoxy-and 4,4′-dihydroxy-3,5-dimethoxybibenzyl.