- Orienting effect of the cage addends: The case of nucleophilic cyclopropanation of C2-C70(CF3)8
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C2-C70(CF3)8 was found to be a very promising substrate in the Bingel and the Bingel-Hirsch reactions combining perfect regioselectivity with much higher reactivity compared to its analogs. The reactions with diethyl malonate yield a single isomer of the monoadduct C70(CF3)8[C(CO2Et)2] and a single C2-symmetrical bisadduct C70(CF3)8[C(CO2Et)2]2. The Bingel-Hirsch variation is particularly interesting in that it additionally affords, in a similar regioselective manner, the unexpected alkylated derivatives C70(CF3)8[CH(CO2Et)2]H and C70(CF3)8[C(CO2Et)2][CH(CO2Et)2]H. The novel compounds have been isolated and structurally characterized by means of 1H and 19F NMR spectroscopy as well as single-crystal X-ray diffraction. The mechanistic and regiochemical aspects of the reaction are explained with the aid of DFT calculations. Conventional vs. unconventional: Acceptor-derivatized fullerene substrates can exhibit an enhanced reactivity and regioselectivity in important organic reactions. Bingel and Bingel-Hirsch functionalization of C2-C70(CF3)8 are reported, which affords rapid and LUMO-directed regioselective formation of both conventional cyclopropanated and unusual alkylated products. The mechanistic and regiochemical aspects of the reaction are explained with the aid of the DFT calculations.
- Apenova, Marina G.,Semivrazhskaya, Olesya O.,Borkovskaya, Eugenia V.,Belov, Nikita M.,Ioffe, Ilya N.,Markov, Vitaliy Yu.,Troyanov, Sergey I.,Lukonina, Natalia S.,Sidorov, Lev N.,Goryunkov, Alexey A.
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- 2-methoxyphenoxy pyrimidine antitumor compound as well as preparation method and application thereof
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The invention belongs to the technical field of medicines, relates to a compound with anti-tumor activity and a specific chemical structure, and particularly relates to a 2-methoxyphenoxy pyrimidine compound as well as a preparation method and application thereof. The structural general formula of the 2-methoxyphenoxy pyrimidine compound is shown in the specification, wherein an R group is a hydrogen atom, or a 2-position monosubstituted fluorine atom, or 3-position and 4-position monosubstituted methyl, methoxy, fluorine atom, chlorine atom, bromine atom and iodine atom. Experimental research shows that the prepared 2-methoxyphenoxy pyrimidine compound shows a good result in an in-vitro anti-tumor activity test, has certain inhibitory activity on human malignant melanoma A375 cells, can be used for preparing anti-tumor drugs, and opens up a new way for developing new anti-tumor drugs. The preparation method provided by the invention is simple and feasible, relatively high in yield and easy for large-scale production.
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Paragraph 0045-0047
(2021/05/12)
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- Phenyl pyrimidinamine anti-tumor compound as well as preparation method and application thereof
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The invention belongs to the technical field of medicines, relates to a compound with anti-tumor activity and a specific chemical structure, and particularly relates to a phenyl pyrimidinamine compound as well as a preparation method and application thereof. The structural general formula of the phenyl pyrimidinamine compound is shown in the specification, wherein an R group is a hydrogen atom, a 2-position monosubstituted fluorine atom, or 3-position and 4-position monosubstituted methyl, a fluorine atom, a chlorine atom and a bromine atom. Experimental research shows that the prepared phenyl pyrimidinamine compound shows a good result in an in-vitro anti-tumor activity test, can be used for preparing anti-tumor drugs, and opens up a new way for developing the anti-tumor drugs with an endothelin receptor as a new target. The preparation method provided by the invention is simple and feasible, higher in yield and easy for large-scale production.
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Paragraph 0045-0047
(2021/06/06)
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- NBS/DBU-Promoted One-Pot Three-Component Cycloaddition of Malonic Acid Derivatives, Nitrosoarenes, and Alkenes: Synthesis of Isoxazolidines
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A general DBU-mediated one-pot three-component cycloaddition reaction of easily accessible malonic acid derivatives, nitrosoarenes, and alkenes has been successfully established with the aid of NBS to provide direct access to highly functionalized isoxazolidine derivatives with generally good to excellent yields, broad functional group tolerance, and excellent regio- and diastereo-selectivities under mild conditions. The mechanism study shows that the NBS-mediated formation of bromomalonic acid derivatives from malonic acid derivatives and DBU-promoted synthesis of nitrone intermediates via the reaction of bromomalonic acid derivatives with nitrosoarenes are key steps.
- Li, Xing,Zheng, Leijie,Gong, Xiaolei,Chang, Honghong,Gao, Wenchao,Wei, Wenlong
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p. 1096 - 1107
(2021/01/14)
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- Novel Allosteric Inhibitors of Deoxyhypusine Synthase against Malignant Melanoma: Design, Synthesis, and Biological Evaluation
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Based on the novel allosteric site of deoxyhypusine synthase (DHPS), two series of 30 novel 5-(2-methoxyphenoxy)-2-phenylpyrimidin-4-amine derivatives as DHPS inhibitors were designed and synthesized. Among them, compound8m, with the best DHPS inhibitory potency (IC50= 0.014 μM), exhibited excellent inhibition against melanoma cells, which was superior to that of GC7. Besides, molecular docking and molecular dynamics (MD) simulations further proved that compound8mwas tightly bound to the allosteric site of DHPS. Flow cytometric analysis and enzyme-linked immunosorbent assay (ELISA) showed that compound8mcould inhibit the intracellular reactive oxygen species (ROS) level. Furthermore, by western blot analysis, compound8meffectively activated caspase 3 and decreased the expressions of GP-100, tyrosinase, eIF5A2, MMP2, and MMP9. Moreover, both Transwell analysis and wound healing analysis showed that compound8mcould inhibit the invasion and migration of melanoma cells. In thein vivostudy, the tumor xenograft model showed that compound8meffectively inhibited melanoma development with low toxicity.
- Li, Shuai,Li, Xin-Yang,Li, Yu-Heng,Lin, Qi-Qi,Liu, Kai-Li,Meng, Fan-Hao,Qian, Xin-Hua,Wang, De-Pu,Xue, Wen-Han
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p. 13356 - 13372
(2021/09/20)
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- Acridine Orange Hemi(Zinc Chloride) Salt as a Lewis Acid-Photoredox Hybrid Catalyst for the Generation of α-Carbonyl Radicals
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A readily accessible organic-inorganic hybrid catalyst is reported for the reductive fragmentation of α-halocarbonyl compounds. The robust hybrid catalyst is a self-stabilizing combination of ZnCl2 Lewis acid and acridine orange as the photoactive organic dye. Mechanistic specifics of this hybrid catalyst have been studied in detail using both photophysical and electrochemical experiments. A systematic study enabled the discovery of the appropriate Lewis acid for the effective LUMO stabilization of α-halocarbonyl compounds and thereby lowering of reduction potential within the range of a standard organic dye. This strategy resolves the issues like dehalogenative hydrogenation or homo-coupling of alkyl radicals by guiding the photoredox cycle through an oxidative quenching pathway. The cooperativity between the photoactive organic dye and the Lewis acid counterparts empowers functionalization with a wide range of coupling partners through efficient and controlled generation of alkyl radicals and serves as an appropriate alternative to the expensive late transition metal-based photocatalysts. To demonstrate the application potential of this cooperative catalytic system, four different synthetic transformations of α-carbonyl bromides were explored with broad substrate scopes.
- Das, Sanju,De Sarkar, Suman,Mandal, Tanumoy
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supporting information
(2021/12/10)
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- Alkyl Halides via Visible Light Mediated Dehalogenation
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Net selective bromination and chlorination of activated C-H bonds can be effected in generally high yield via a simple perhalogenation/dehalogenation sequence. The photochemical reductions require no photocatalyst, relying instead on the formation of an electron donor-acceptor complex of the substrate and reductant, or alternatively autophotocatalysis. Some reactions proceed despite any apparent photon absorption, serving as a cautionary tale for other photochemical reactions involving amines. Mechanistic experiments provide an explanation for this observation.
- Rathnayake, Manjula D.,Weaver, Jimmie D.
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p. 9681 - 9687
(2019/11/28)
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- Synthetic routes for a variety of halogenated (chiral) acetic acids from diethyl malonate
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Chiral halomethane is the smallest stable molecule with a single asymmetric C-atom and halogenated acetic acids often serve as precursors. We focus on a synthetic route to synthesise chiral halogenated acetic acids with F, Cl, Br, and H/D isotopic substitution at the α-C-atom starting from diethyl malonate. This reactant is easily available, cheap and allows the obtainment of target acids in a few reaction steps with great versatility. Among all of the possible fully halogenated acetic acids (more than one hundred, which are, in principle, accessible by this route), there are only a small number of chiral halogenated acetic acids, which have been synthesized following the devised synthetic route.
- Mazenauer, Manuel R.,Manov, Stole,Galati, Vanessa M.,Kappeler, Philipp,Stohner, Jürgen
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p. 55434 - 55440
(2018/04/05)
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- Enantioselective cyclopropanation of (Z)-3-substituted-2-(4-pyridyl)-acrylonitriles catalyzed by Cinchona ammonium salts
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Cyclopropane esters holding two quaternary centres were prepared in high yields, complete diastereoselection and up to 83% ee. The reaction described herein entailed reacting (Z)-3-substituted-2-(4-pyridyl)-acrylonitrile, a reactive class of Michael acceptor, with 2-bromomalonate esters in the presence of Cinchona derived phase-transfer catalysts. The reaction allowed multi-gram preparation of the desired products.
- Del Fiandra, Claudia,Moccia, Maria,Adamo, Mauro F. A.
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supporting information
p. 3105 - 3111
(2016/03/19)
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- Preparation method for 2-halogenated-1,3-dicarbonyl derivative
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The invention discloses a preparation method for a 2-halogenated-1,3-dicarbonyl derivative. The preparation method is suitable for wide 1,3-dicarbonyl derivatives. The raw materials are easy to obtain, and multiple varieties are achieved. The product obtained through the method is diversified in type, and can be directly used and used for other further reactions. According to the method, reaction conditions are gentle, the reaction operation and after-treatment process is simple, reaction time is short, the yield is high, pollution is low, and the preparation method is suitable for industrial production.
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Paragraph 0048
(2017/02/28)
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- Flash preparation of carbenoids: A different performance of cyanogen bromide
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Cyanogen halides are known substances for the cyanating reaction. There are a few evidences for bromination reaction too. On the other hand carbenes are known as very important substances due to their remarkable reactions. Unfortunately carbenes at room temperature are very unstable and there is not a simple method for preparation of them. In most cases the isolation is not possible. We have reported a new reliable and fast preparation method of almost stable carbenoids. The mechanism of the formation has been discussed.
- Hedayati, Mohammad Jalilzadeh,Pesyan, Nader Noroozi
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p. 2081 - 2089
(2015/04/22)
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- Facile and efficient method for oc-monobromination of dicarbonyl compounds with N-bromosuccinimide
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The a-monobrominated products were prepared fast in presence of p-TsOH as catalyst in very high yields using various 1,3-diketones and β-keto-esters with N-bromosuccinimide in CH2C12.
- Fang, Li-Zhen,Shen, Jiu-Ming,Lv, Qing-Hua,Yan, Fu-Lin
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experimental part
p. 3425 - 3427
(2012/02/04)
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- One-pot new barbituric acid derivatives derived from the reaction of barbituric acids with BrCN and ketones
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Reaction of cyclic β-dicarbonyl compounds such as pyrimidine-(1 H,3H,5H)-2,4,6-trione (BA), 1,3-dimethyl pyrimidine-(1 H,3H,5H)-2,4,6-trione (DMBA) and 2-thioxo-pyrimidine-(1 H,3H,5H)-4,6-dione (TBA) with cyanogen bromide in acetone and 2-butanone in the presence of triethylamine afforded a new class of stable heterocyclic spiro[furo[2,3-d]pyrimidine-6,5′-pyrimidine]2, 2′,4,4′,6′(3H,3′H,5H)-penta-ones (dimeric forms of barbiturate) at 0 °C and ambient temperature. Structure elucidation was carried out by X-ray crystallographic, 1H NMR, 13C NMR, two dimensional NMR, FT-IR spectra, mass spectrometry and elemental analysis. The mechanism of product formation is discussed. The reaction of DMBA with cyanogen bromide in the presence of triethylamine also afforded trimeric form of barbiturate of uracil derivatives in good yield. The reaction of selected acyclic β-dicarbonyl compounds with cyanogen bromide in the presence of triethylamine in acetone and/or diethyl ether has also been investigated under the same condition. Diethyl malonate and ethyl cyanoacetate brominated and also ethyl acetocetate both bro-minated and cyanated on active methylene via cyanogen bromide.
- Hosseini, Yaser,Rastgar, Saeed,Zerrin Heren,Orhan Büyükgüng?r,Pesyan, Nader Noroozi
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experimental part
p. 309 - 318
(2011/11/06)
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- Ethylenebis(N-methylimidazolium) ditribromide (EBMIDTB): An efficient reagent for the monobromination of 1,3-diketones and β-ketoesters
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Ethylenebis(N-methylimidazolium) ditribromide, a stable crystalline solid, is easily prepared by reaction of the corresponding dibromide salt with bromine in n-hexane. 1,3-Diketones and β-ketoesters can be brominated chemoselectively to the corresponding α-monobrominated products by using this reagent at 0-5°C. Under the same reaction conditions, diethyl malonate, ethyl cyanoacetate, and malonitrile were monobrominated at moderate yield.
- Hosseinzadeh, Rahman,Tajbakhsh, Mahmood,Mohadjerani, Maryam,Lasemi, Zahra
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experimental part
p. 57 - 60
(2010/03/30)
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- Rapid and catalyst-free α-halogenation of ketones using N-halosuccinamides in DMSO
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α-Halogenation of various carbonyl compounds such as β-keto-esters, cyclic ketones, and lactams with N-halosuccinamides (NBS, NCS, NIS) in the presence of DMSO proceeded very smoothly to give the corresponding α-monohalogenated products in good to excellent yields with high selectivity under catalyst-free conditions. Copyright Taylor & Francis Group, LLC.
- Sreedhar,Reddy, P. Surendra,Madhavi
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p. 4149 - 4156
(2008/03/13)
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- New synthesis of polyfluoroalkyl racemic α-amino acids
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We describe here a new synthesis of racemic α-amino acids containing polyfluorinated aliphatic long chain RF(CH2)3Y (RF = C2F5, C6F13, C 8F17) (Y = CH(NH2)COOH) based on So?rensen's method. The radical addition of perfluoroalkyl iodides R FI (RF = C2F5, C6F 13, C8F17) at room temperature to ethyl-2-carbetoxy-2-phthalimido-pent-4-enoate 3 was first initiated by Et 3B/O2. Then, the reduction of adducts 4a-c using Et 3B/O2/Bu3SnH leads to ethyl-2-carbetoxy-2- phthalimido-5-perfluoroalkyl-pentanoate 5a-c under mild conditions. Experimental conditions for optimisation of the iodoperfluoroalkylation step using Et 3B/O2 were studied. Finally, deprotection of 5a-c gave the desired products 6a-c in good yields.
- Delon,Laurent,Blancou
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p. 1487 - 1492
(2007/10/03)
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- Poly(vinylpyrrolidone)-bromine complex; a mild and efficient reagent for selective bromination of alkenes and oxidation of alcohols
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Poly(vinylpyrrolidone)-bromine complex (PVP-Br2) is easily prepared and used as a mild and convenient reagent for selective bromination of alkenes and at the position α-hydrogen of active carbonyl compounds. Selective oxidation of benzylic alcohols in the presence of aliphatic alcohols were also achieved at room temperature.
- Lakouraj, Moslem Mansour,Tajbakhsh, Mahmood,Mokhtary, Masoud
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p. 481 - 483
(2007/10/03)
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- The synthetic versatility of alkoxycarbonyl- and hydroxymethyl-piperazine- 2,5-diones
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Alkoxycarbonylpiperazine-2,5-diones are versatile precursors for the α-functionalisation of piperazine-2,5-diones. The alkoxycarbonyl group activates the α-carbon position to alkylation reactions and this provides a mild and selective method for the extension of the carbon framework of piperazine-2,5-diones. In addition, the alkoxycarbonyl group can be converted to the carboxy group, which in turn can be 'deleted' or manipulated for the installation of carbon and/or heteroatom substituents where desired, the latter via N-acyliminium chemistry. We also demonstrate that hydroxymethylpiperazine-2, 5-diones complement carboxypiperazinediones as precursors for the generation of N-acyliminium ions.
- Chai, Christina L.L.,Elix, John A.,Huleatt, Paul B.
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p. 8722 - 8739
(2007/10/03)
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- Efficient microwave induced direct α-halogenation of carbonyl compounds
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A novel and direct method for the synthesis of α-halocarbonyl compounds using sequential treatment of carbonyl compounds with [hydroxy(tosyloxy)iodo]benzene followed by magnesium halides under solvent-free microwave irradiation conditions is described.
- Lee, Jong Chan,Park, Jin Young,Yoon, So Young,Bae, Yong Hun,Lee, Seung Jun
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p. 191 - 193
(2007/10/03)
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- Reactions of diethyl dibromomalonate and ethyl 2,2-dichloroacetoacetate with water and carbonyl compounds (aldehydes and ketones) in the presence of pentacarbonyliron
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Diethyl dibromomalonate and ethyl 2,2-dichloroacetoacetate are effectively reduced with the system pentacarbonyliron-proton-donor compound (water or butyl methyl ketone) to give the corresponding hydrodehalogenation products. These results provide a support for the previous assumption that the key reaction stage is reduction with pentacarbonyliron of initially formed radical to anion which is then involved in proton transfer.
- Terent'ev,Vasil'eva,Mysova,Chakhovskaya
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p. 924 - 927
(2007/10/03)
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- Bromination by means of sodium monobromoisocyanurate (SMBI)
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A variety of aromatic compounds with both activating and deactivating substituents were brominated with sodium monobromoisocyanurate (SMBI) 1, diethyl ether, diethyl ether-methanesulfonic acid, trifluoroacetic acid, or sulfuric acid were employed as solvents. Thus nitrobenzene was conveniently brominated in sulfuric acid, benzene was readily monobrominated in diethyl ether-methanesulfonic acid, and phenol was selectively brominated at the ortho position under mild conditions in refluxing diethyl ether. With substituents that are easily protonated, trifluoroacetic acid may be employed as solvent in the reaction with 1, in contrast NBS was ineffective in trifluoroacetic acid. This renders 1 a superior reagent relative to NBS. In addition to aromatics, alkenes, ketones and esters were also brominated with 1. Diethyl malonate was brominated with 1 and then subjected to a Bingel reaction with NaH to afford the desired methanofullerene in reasonable yield.
- Okada, Yukihiro,Yokozawa, Masanori,Akiba, Miwa,Oishi, Kazuhiko,O-Kawa, Kyoji,Akeboshi, Tomohiro,Kawamura, Yasuo,Inokuma, Seiichi,Nakamura, Yosuke,Nishimura, Jun
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p. 2506 - 2511
(2007/10/03)
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- Aminopolycarboxylates, process for producing the same and use thereof
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An aminopolycarboxylate is described, which is represented by the following formula (1): wherein M1, M2, M3 and M4 independently represent each an alkali metal ion. A process for producing the aminopolycarboxylate; a biodegradable chelating agent which comprises as the active component the aminopolycarboxylate; and a sequestering agent which comprises as the active component the aminopolycarboxylate are also described.
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- One-Pot synthesis of 5-Alkylthio-3H-1,2-dithiole-3-thiones: Advantages and scopes
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The reaction of dialkyl malonate esters with P2S5/S8 in boiling xylene in the presence of 2-mercaptobenzothiazole/ZnO as catalyst produces 5-alkylthio-3H-1,2-dithiole-3-thiones as major identifiable product. Moderate yields were obtained with malonate esters of primary alcohols. The reaction fails with malonate esters of secondary alcohols. Regarding the substituent in position two, dialkyl malonates with groups such as CH3, Ph, CH2Ph, OCH3 and Cl afford the corresponding 4-substituted derivatives whereas with Br and NO2 do not give the expected products. Some mechanistic evidences are described.
- Aimar,De Rossi
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p. 1749 - 1755
(2007/10/03)
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- Reaction of diethyl dibromomalonate with methoxide: Evidence for a novel bromophilic attack
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Reaction of diethyl dibromomalonate (1) with sodium methoxide in cyclohexene yields dibromonorcarane (2) as the major product. This product forms via the capture of dibromocarbene (4) by cyclohexene. Dibromocarbene, in turn, is generated from ethyl tribromoacetate (6) which evidence suggests arises via a bromophilic attack between the carboethoxydibromomethyl carbanion (7) and diethyldibromomalonate (1).
- Mebane, Robert C.,Smith, Keegan M.,Rucker, Darlene R.,Foster, Michael P.
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p. 1459 - 1462
(2007/10/03)
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- A Convenient Halogenation Procedure for the Preparation of α-Halocarbonyl Compounds
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Except for substituted acetophenones (p-Y-C6H4COCH3, Y=H, Br, CH3O), simple ketones, α-ketoesters and 1,3-diketones reacted smoothly with a preformed homogeneous mixture of hydrochloric acid and potassium permanganate in acetonitrile to give moderate to good yields of the corresponding α-chlorocarbonyl compounds.Mixtures of α-chloro- and α,α-dichlorocarbonyl compounds were obtained for substituted acetophenones.Brominations proceeded similarly with higher yields when the hydrochloric acid was replaced with hydrobromic acid. - Key words: α-chlorocarbonyl compounds; α-bromocarbonyl compounds; potassium permanganate; chlorination; bromination.
- Cheng, Sheng-Fan,Lin, Ching-Shan,Liu, Lilian Kao
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p. 309 - 312
(2007/10/03)
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- Synthesis of cyclic halooxatelluranes via dehalogenation of α-halo carbonyl compounds with tellurides containing hydroxy group on side chain
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The synthesis of cyclic halooxatelluranes (3a, 4a-d, 5a) has been achieved via dehalogenation of α-halo carbonyl compounds (2A-F) with tellurides(1a-d) containing hydroxy group on the side chain. Halophilicity of the tellurides was compared with that of selenides and a plausible reaction mechanism is discussed.
- Zhang, Jian,Saito, Shinichi,Takahashi, Tamiko,Koizumi, Toru
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p. 575 - 584
(2007/10/03)
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- CHEMISTRY OF NITRO ESTERS XVII. METHOD FOR THE PRODUCTION OF MESOXALIC ESTERS
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A new preparative method was developed for the production of mesoxalic esters from bromomalonic esters and silver nitrate
- Kochergin, P. M.,Titkova, R. M.
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p. 1042 - 1044
(2007/10/02)
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- Mild Halogenation of Stabilized Ester Enolates by Cupric Halides
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The reactions of various stabilized ester enolates of 2-keto, 2-(alkoxycarbonyl), 2-phosphoryl, and 2-(benzenesulfonyl) esters with cupric chloride or cupric bromide have been examined.The reactions lead to 2-halo esters in good to excellent yields under mild condition.Enolates which contain an unsaturated functionality such as a double bond, a triple bond, or an allylic or a benzylic moiety react with high chemoselectivity.
- Shi, Xiao-Xin,Dai, Li Xin
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p. 4596 - 4598
(2007/10/02)
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- Formation of isoxazolines N-oxides and dihydrofurans from a cyclocondensation between bromo or chloromalonate carbanion and Michael acceptors
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Heterocyclic compounds are prepared by a cyclocondensation reaction between halomalonate carbanion and Michael acceptors : α-nitroalkenes lead to isoxazolines N-oxides and α,β-unsaturated carbonyl derivatives to dihydrofurans.Formation of the carbanion results from deprotonation of monohalomalonates with powdered potassium carbonate in THF; as a rule; chloromalonate affords better yields than bromomalonate.Key Words: halomalonate carbanions / electrophilic alkenes / dihydrofurans / isoxazolines N-oxide
- Menn, J. C. Le,Sarrazin, J.,Tallec, A.
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p. 562 - 565
(2007/10/02)
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- Reactions of Perfluoroalkanesulfonyl Bromide
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Perfluoroalkanesulfonyl bromides were readily prepared from the reaction of the corresponding sodium sulfinates with bromine in aqueous solution in excellent yield.Several reactions of these sulfonyl bromides were reported: 1.Spontaneous addition to olefin with the loss of sulfur dioxide to give the corresponding adducts in good yield. 2.Facile bromination of compounds containing active hydrogen. 3.Reaction with alcohol, amines and alkali.
- Huang, Wei-Yuan,Chen, Jian-Long,Hu, Li-Qing
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p. 881 - 884
(2007/10/02)
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- Electron Ionization and Chemical Ionization Mass Spectra of Pyridinium and Isoquinolinium Ylides
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Electron ionization (EI) spectra and both positive and negative chemical ionization (CI) spectra have been obtained for four isoquinolinium ylides and two pyridinium ylides.Electron transfer reactions dominate the CI mass spectra.The base peak in negative chemical ionization is the ., is relatively more intense than + showing electron transfer to be the main positive ionization process.In the positive ammonia CI spectra, proton transfer to give + is the main ionization process, but electron transfer is also observed.The EI spectra show fragmentations in which the aromatic nitrogen moiety retains the charge and fragmentation is by loss of radicals or small neutral molecules from the side-chains.Radical driven reactions are proposed to explain these spectra.
- Bowen, D. V.,Skett, P. W.,Thorpe, J.,Plunkett, A. O.
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p. 285 - 290
(2007/10/02)
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- The biosynthesis of the streptolidine moiety in streptothricin F
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A series of arginines specifically labeled either with 13C and 15N or with 2H were synthesized and fed to Streptomyces L-1689-23. The streptothricin F isolated in each case was analyzed by either 13C or 2H NMR, respectively, in order to determine the labeling pattern obtained. From these results, it appears that arginine is metabolized to a β-ketoarginine, possibly via a pyridoxal phosphate adduct, and then via cyclization, reduction, rearrangement, and hydroxylation to the streptolidine moiety. The pathway described can also account for the formation of other known antibiotics, and for β-hydroxy-γ-amino acids, generally.
- Martinkus,Tann,Gould
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p. 3493 - 3505
(2007/10/02)
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