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Georgiev A, Deneva V, Yordanov D, Völzer T, Wolter S, Fennel F, Lochbrunner S, Antonov L. Benzothiazol picolin/isonicotinamides molecular switches: Expectations and reality. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.118968] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Kroonblawd MP, Lindsey RK, Goldman N. Synthesis of functionalized nitrogen-containing polycyclic aromatic hydrocarbons and other prebiotic compounds in impacting glycine solutions. Chem Sci 2019; 10:6091-6098. [PMID: 31360414 PMCID: PMC6585877 DOI: 10.1039/c9sc00155g] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Accepted: 05/19/2019] [Indexed: 01/09/2023] Open
Abstract
Proteinogenic amino acids can be produced on or delivered to a planet via impacting abiotic sources and consequently were likely present before the emergence of life on Earth. However, the role that these materials played in prebiotic scenarios remains an open question, in part because little is known about the survivability and reactivity of astrophysical organic compounds upon impact with a planetary surface. To this end, we use a force-matched semi-empirical quantum simulation method to study impacts of aqueous proteinogenic amino acids at conditions reaching 48 GPa and 3000 K. Here, we probe a relatively unstudied mechanism for prebiotic synthesis where sudden heating and pressurization causes condensation of complex carbon-rich structures from mixtures of glycine, the simplest protein-forming amino acid. These carbon-containing clusters are stable on short timescales and undergo a fundamental structural transition upon expansion and cooling from predominantly sp3-bonded tetrahedral-like moieties to those that are more sp2-bonded and planar. The recovered sp2-bonded structures include large nitrogen containing polycyclic aromatic hydrocarbons (NPAHs) with a number of different functional groups and embedded bonded regions akin to oligo-peptides. A number of small organic molecules with prebiotic relevance are also predicted to form. This work presents an alternate route to gas-phase synthesis for the formation of NPAHs of high complexity and highlights the significance of both the thermodynamic path and local chemical self-assembly in forming prebiotic species during shock synthesis. Our results help determine the role of comets and other celestial bodies in both the delivery and synthesis of potentially significant life building compounds on early Earth.
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Affiliation(s)
- Matthew P Kroonblawd
- Physical and Life Sciences Directorate , Lawrence Livermore National Laboratory , Livermore , CA 94550 , USA .
| | - Rebecca K Lindsey
- Physical and Life Sciences Directorate , Lawrence Livermore National Laboratory , Livermore , CA 94550 , USA .
| | - Nir Goldman
- Physical and Life Sciences Directorate , Lawrence Livermore National Laboratory , Livermore , CA 94550 , USA .
- Department of Chemical Engineering , University of California , Davis , California 95616 , USA
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Yang H, Kim TH, Park KM, Kim J. Acrinathrin: (S)-cyano-(3-phen-oxy-phenyl)methyl (Z)-(1R,3S)-2,2-dimethyl-3-{2-[2,2,2-trifluoro-1-(trifluoro-methyl)eth-oxy-carbon-yl]vin-yl}cyclo-propane-1-carboxyl-ate. Acta Crystallogr Sect E Struct Rep Online 2011; 67:o1275. [PMID: 21754558 PMCID: PMC3089073 DOI: 10.1107/s1600536811014760] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Accepted: 04/20/2011] [Indexed: 11/25/2022]
Abstract
In the title compound, C26H21F6NO5, the dihedral angle between the cyclopropane ring plane and the vinyl group plane is 79.3 (3)°. The dihedral angle between the benzene and phenyl ring planes in the phenoxybenzyl group is 82.7 (1)°. In the crystal structure, weak intermolecular C—H⋯π interactions and C—H⋯F hydrogen bonds contribute to the stabilization of the packing.
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Affiliation(s)
- Hojin Yang
- Department of Chemistry and Research Institute of Natural Sciences, Gyeongsang National University, Jinju 660-701, Republic of Korea
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4
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Basheer A, Mishima M, Rappoport Z. Enols of 2-nitro- and related 2-substituted malonamides. J PHYS ORG CHEM 2009. [DOI: 10.1002/poc.1611] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Malamidou-Xenikaki E, Spyroudis S, Tsanakopoulou M, Krautscheid H. Enamino Derivatives of 1,3-Dioxoindane-2-carboxylic Acid. J Org Chem 2008; 73:8392-7. [DOI: 10.1021/jo8014903] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Elizabeth Malamidou-Xenikaki
- Department of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece, and Institute of Inorganic Chemistry, University of Leipzig, D-04103 Leipzig, Germany
| | - Spyros Spyroudis
- Department of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece, and Institute of Inorganic Chemistry, University of Leipzig, D-04103 Leipzig, Germany
| | - Maria Tsanakopoulou
- Department of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece, and Institute of Inorganic Chemistry, University of Leipzig, D-04103 Leipzig, Germany
| | - Harald Krautscheid
- Department of Chemistry, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece, and Institute of Inorganic Chemistry, University of Leipzig, D-04103 Leipzig, Germany
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6
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Basheer A, Rappoport Z. Thioenols and thioamides substituted by twoβ-EWGs. Comparison with analogous amides and enols. J PHYS ORG CHEM 2008. [DOI: 10.1002/poc.1359] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Fröhlich J, Berger S. The Use of NMR Chemical Shifts to Predict Reaction Pathways: Methanol Formation from Oxazolidinones. European J Org Chem 2008. [DOI: 10.1002/ejoc.200701036] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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Basheer A, Rappoport Z. Enols and thioenols of substituted cyanomonothiocarbonylmalonamides: structures, enolization vs. thioenolization, equilibria and conformations. Org Biomol Chem 2008; 6:1071-82. [DOI: 10.1039/b717556f] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Basheer A, Rappoport Z. Oxa-ene Reaction of Enols of Amides with 4-Phenyl-1,2,4-triazoline-3,5-dione. J Org Chem 2007; 73:184-90. [DOI: 10.1021/jo702083u] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ahmad Basheer
- Department of Organic Chemistry and the Lise Meitner Minerva Center for Computational Quantum Chemistry, The Hebrew University, Jerusalem 91904, Israel
| | - Zvi Rappoport
- Department of Organic Chemistry and the Lise Meitner Minerva Center for Computational Quantum Chemistry, The Hebrew University, Jerusalem 91904, Israel
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Song J, Lei YX, Rappoport Z. The First Solid Enols of Anhydrides. Structure, Properties, and Enol/Anhydride Equilibria1. J Org Chem 2007; 72:9152-62. [DOI: 10.1021/jo071206m] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Jinhua Song
- Department of Organic Chemistry and the Lise Meitner Minerva Center for Computational Quantum Chemistry, The Hebrew University, Jerusalem 91904, Israel
| | - Yi Xiong Lei
- Department of Organic Chemistry and the Lise Meitner Minerva Center for Computational Quantum Chemistry, The Hebrew University, Jerusalem 91904, Israel
| | - Zvi Rappoport
- Department of Organic Chemistry and the Lise Meitner Minerva Center for Computational Quantum Chemistry, The Hebrew University, Jerusalem 91904, Israel
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Song J, Yamataka H, Rappoport Z. Dialkoxyphosphinyl-substituted enols of carboxamides. J Org Chem 2007; 72:7605-24. [PMID: 17760461 DOI: 10.1021/jo0710679] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Reactions of isocyanates XNCO (e.g., X = p-An, Ph, i-Pr) with (MeO)2P(=O)CH2CO2R [R = Me, CF3CH2, (CF3)2CH] gave 15 formal "amides" (MeO)2P(=O)CH(CO2R)CONHX (6/7), and with (CF3CH2O)2P(=O)CH2CO2R [R = Me, CF3CH2] they gave eight analogous amide/enols 17/18. X-ray crystallography of two 6/7, R = (CF3)2CH systems revealed Z-enols of amides structures (MeO)2P(=O)C(CO2CH(CF3)2)=C(OH)NHX 7 where the OH is cis and hydrogen bonded to the O=P(OMe)2 group. The solid phosphonates with R = Me, CF3CH2 have the amide 6 structure. The structures in solution were investigated by 1H, 13C, 19F, and 31P NMR spectra. They depend strongly on the substituent R and the solvent and slightly on the N-substituent X. All systems displayed signals for the amide and the E- and Z-isomers. The low-field two delta(OH) and two delta(NH) values served as a probe for the stereochemistry of the enols. The lower field delta(OH) is not always that for the more abundant enol. The % enol, presented as K(enol), was determined by 1H, 19F, and 31P NMR spectra, increases according to the order for R, Me < CF3CH2 < (CF3)2CH, and decreases according to the order of solvents, CCl4 > CDCl3 approximately THF-d8 > CD3CN >DMSO-d6. In DMSO-d6, the product is mostly only the amide, but a few enols with fluorinated ester groups were observed. The Z-isomers are more stable for all the enols 7 with E/Z ratios of 0.31-0.75, 0.15-0.33, and 0.047-0.16 when R = Me, CF3CH2, and (CF3)2CH, respectively, and for compounds 18, R = Me, whereas the E-isomers are more stable than the Z-isomers. Comparison with systems where the O=P(OMe)2 is replaced by a CO2R shows mostly higher K(enol) values for the O=P(OMe)2-substituted systems. A linear correlation exists between delta(OH)[Z-enols] activated by two ester groups and delta(OH)[E-enols] activated by phosphonate and ester groups. Compounds (MeO)2P(=O)CH(CN)CONHX show <or=7.3% enol in CDCl3 solution. For [(MeO)2P(=O)]2CHCONHX, activated by two O=P(OMe)2 groups, only the amides were observed in solution and in the solid. DFT calculations reproduce the general effect of R on Kenol, but the correlation between observed and calculated Kenol values is not linear. The roles of electron withdrawal by the activating phosphonate and ester groups, and the importance of N-H and O-H hydrogen bonding to them in stabilizing the enols are discussed.
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Affiliation(s)
- Jinhua Song
- Department of Organic Chemistry and the Lise Meitner Minerva Center for Computational Quantum Chemistry, The Hebrew University, Jerusalem 91904, Israel
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Song J, Mishima M, Rappoport Z. Isomeric Solid Enols on Ring- and Amide-Carbonyls of Substituted 2-Carbanilido-1,3-indandiones. Org Lett 2007; 9:4307-10. [PMID: 17880230 DOI: 10.1021/ol7018554] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Both isomeric enols on ring carbonyl (5b) and on amide carbonyl (6b) derived from N-p-methoxyphenyl-2-carbamido-1,3-indandione (4b) were isolated, and their X-ray structures were determined. X-ray diffraction of the N-o,p-dimethoxy analogue indicated a disorder ascribed to the presence of a 6:4 mixture of 5c and 6c. Calculation (B3LYP/6-31+G*) gave good agreement with observed geometries. The calculated energies indicated that enols 6 are more stable by <1 kcal/mol than enols 5 and much more stable than amides 4.
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Affiliation(s)
- Jinhua Song
- Department of Organic Chemistry, The Hebrew University, Jerusalem 91904, Israel
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13
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Basheer A, Yamataka H, Ammal SC, Rappoport Z. Enols of Substituted Cyanomalonamides. J Org Chem 2007; 72:5297-312. [PMID: 17559283 DOI: 10.1021/jo070877h] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Twenty open-chain mono-, di-, and trialkyl and aryl-N-substituted cyanomalonamides R2R1NCOCH(CN)CONHR3 were prepared. In solution, signals for both amide and a single enol are mostly observed, despite the potential for E and Z isomeric enols. The equilibrium (KEnol) values between the amides and the enols were determined in different solvents by NMR spectra. They decrease on increasing the polarity of the solvent in the order CDCl3 approximately C6D6>THF-d8>(CD3)2CO>CD3CN>DMF-d7>DMSO-d6. For the R1R2NCOCH(CN)CONHR3 system when R1=R2=H, Me or R1=H, R2=Me, KEnol for R3 follows the order: C6F5>Ph>or=An>or= i-Pr>or= t-Bu, and for R1, R2:H, H>Me, H>Me, Me in all solvents. A unique feature is the appreciable % enol in DMSO-d6 when R1=R2=H, in contrast with enol systems with other electron-withdrawing groups (EWGs). Calculations (B3LYP/6-31G**) corroborate the higher KEnol values for less alkyl-substituted systems, showing that in the most stable conformer when R1=H, R2=R3=Me the N-hydrogens are closer to the CN group. The order of promoting substituents for enol of amide formation is CONH2>CO2CH2CF3>CO2Me>CONHMe. The solid-state structures of the isolated species, determined by X-ray crystallography, were either amides or enols, and a higher KEnol(CDCl3) value does not ensure a solid enol structure. In no system were both solid species isolated. The X-ray structures of the enols were temperature-dependent. In most cases, the difference between the O-H and O...H bond lengths at low temperature were appreciable, but they become closer at the higher temperature. Similar tendency for either the C=C/C-C or the C-O/C=O bonds was observed. This is ascribed to a hydrogen shift between two regioisomeric enols in an asymmetric double-well potential, which becomes faster at a higher temperature. Calculations show that the enol structures are nonsymmetrical, resembling the lower temperature structures, even when they are chemically symmetrical, but the energy differences between the two regioisomers are <1 kcal. The hydrogen bonds in the enol moiety are strong, with O...O distances <2.45 A, and are resonance-assisted hydrogen bonds. IR spectra in solution and the solid state qualitatively corroborate the NMR and X-ray structure determination.
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Affiliation(s)
- Ahmad Basheer
- Department of Organic Chemistry, The Hebrew University, Jerusalem 91904, Israel
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14
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Morales-Ríos MS, López-Camacho PY, Suárez-Castillo OR, Joseph-Nathan P. Trapping enols of esters and lactones with diazomethane. Tetrahedron Lett 2007. [DOI: 10.1016/j.tetlet.2007.02.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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15
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Abstract
[Structure: see text] The first example of a crystalline amide and its tautomeric enol was obtained for the amide MeNHCSCH(CN)CONHMe (8) and its enol MeNHCSC(CN)=C(OH)NHMe (9). Their X-ray structures were determined, and their structural features resemble those of other related amides and enols. No other example of a similar pair was obtained. In solution, both 8 and 9 and a small percentage of the isomeric enol of thioamide MeNHCOC(CN)=C(SH)NHMe (10) were obtained in solvent-dependent compositions, which are rapidly established.
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Affiliation(s)
- Ahmad Basheer
- Department of Organic Chemistry, The Hebrew University, Jerusalem 91904, Israel
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16
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Basheer A, Rappoport Z. Substituted 2-Methylene-1,3-oxazolidines, -1,3-thiazolidines, -1,3-benzothiazines, -1,3-oxazines, and Substituted Imidazopyrimidinediones from Cl(CH2)nNCO and Cl(CH2)nNCS and Active Methylene Compounds. J Org Chem 2006; 71:9743-50. [PMID: 17168593 DOI: 10.1021/jo061835g] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The reaction of omega-chloroalkyl isocyanates Cl(CH2)nNCO (n = 2 (2), 3 (4)) and isothiocyanate Cl(CH2)2NCS (3) with active methylene compounds CH2YY' 1 in the presence of Et3N or Na give 2-YY'-methylene-1,3-oxazolidines, (E,Z)-1,3-thiazolidines, and 1,3-oxazines from 2, 3, and 4, respectively. 2-(Chloromethyl)phenyl isocyanate 8 gives with 1 the corresponding benzo-oxazines. Ethyl 2-isothiocyanatobenzoate 10 gives the corresponding benzothiazolinone, whereas the analogous isocyanate 12 gives noncyclic enols. Ethoxycarbonyl isothiocyanate 14 gives an open-chain thioenol or an enol-thioamide. The cyanoamides CH2(CN)CONHR, R = H, Me, CHPh2, give with Et3N and 2 the bicyclic imidazopyrimidinediones 16, derived from two molecules of 2, but with their preformed Na salt they give the 1,3-oxazolidines. Reaction of cyanoacetamide with 3 in the presence of Na gave a tricyclic triaza(thia)indacene, derived from two molecules of 3. A reaction mechanism involving an initial attack of the anion 1- on the N=C=X (X = O, S) moiety gives an anion 18, which cyclizes intramolecularly and after tautomerization gives the mono-ring heterocycle. With the cyanoamides, the N- site of the ambident ion 18 attacks another molecule of 2 giving the anion 20, which by intramolecular attack on the CN, followed by expulsion of the Cl- gives the bicyclic 16 after tautomerization.
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Affiliation(s)
- Ahmad Basheer
- Department of Organic Chemistry, The Hebrew University, Jerusalem 91904, Israel
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Lehner AF, Craig M, Fannin N, Bush L, Tobin T. Electrospray[+] tandem quadrupole mass spectrometry in the elucidation of ergot alkaloids chromatographed by HPLC: screening of grass or forage samples for novel toxic compounds. JOURNAL OF MASS SPECTROMETRY : JMS 2005; 40:1484-502. [PMID: 16278935 DOI: 10.1002/jms.933] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Ergot alkaloids are mycotoxins generated by grass and grain pathogens such as Claviceps, for example. Ergot alkaloid-poisoning syndromes, such as tall fescue toxicosis from endophyte-infected tall fescue grass, are important veterinary problems for cattle, horses, sheep, pigs and chickens, with consequent impact on food, meat and dairy industries. Damage to livestock is of the order of a billion dollars a year in the United States alone. HPLC with UV and fluorescence detection are the predominant means of ergot alkaloid determination, with focus on quantitation of the marker compound ergovaline, although ELISA methods are undergoing investigation. These techniques are excellent for rapid detection, but of poor specificity in defining new or poorly characterized ergot alkaloids and related compounds. This paper demonstrates the facility of using electrospray(+) mass spectrometry with multiple reaction monitoring (MRM) detection during chromatographic examination of ergot alkaloid standards of lysergic acid, lysergol, ergonovine, ergovaline, ergotamine, ergocornine, ergocryptine and ergocrystine by HPLC. Ergoline-8 position epimers could be separated on the gradient HPLC system for ergocornine, ergocrystine and ergonovine and appeared as shoulders for ergotamine and ergovaline; epimers generally showed different patterns of relative intensity for specific MRM transitions. There was reasonable correspondence between retention of standards on the 2-mm ESI(+)MS phenyl-hexyl-based reverse phase column and those on the 4-mm C18-based column. Since up to 10% of clinical cases involving toxin exposure display unidentified chromatographic peaks, 11 samples of feed components associated with such cases were studied with developed MRM methods to attempt elucidation of crucial components if possible. Ergotamine appeared in all, ergovaline appeared in five and ergocornine appeared in six; ergonovine, ergocryptine, ergocrystine and lysergol also appeared in several. In addition, molecular weights of compounds newly revealed by mass spectrometry suggested ergosine, ergostine and ergoptine in four samples, for which standards were not available. Dehydrated products of ergotamine, ergocrystine and ergocornine were discovered, along with dihydrogenated ergocrystine and ergocryptine in seven of the samples, and the issue was raised as to whether dehydration was strictly an instrument-derived artifact. Finally, five of the samples, along with fescue seed standard, evidenced one or more of 14 new ergot alkaloids ranging in size from 381 to 611 molecular weight and with key mass spectral characteristics of ergot alkaloids, specifically the pair of peaks m/z 223 and 208, corresponding to the ergoline ring system and its demethylated variant, respectively. It is anticipated that findings such as these will provide impetus to future development of analytical methodology for these heretofore relatively rare ergot alkaloid species.
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Affiliation(s)
- Andreas F Lehner
- University of Kentucky, College of Agriculture, Livestock Disease Diagnostic Center, Lexington, Kentucky 40512-4125, USA.
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18
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Raczyńska ED, Kosińska W, Ośmiałowski B, Gawinecki R. Tautomeric Equilibria in Relation to Pi-Electron Delocalization. Chem Rev 2005; 105:3561-612. [PMID: 16218561 DOI: 10.1021/cr030087h] [Citation(s) in RCA: 247] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Mishima M, Matsuoka M, Lei YX, Rappoport Z. Gas-Phase Acidities of Disubstituted Methanes and of Enols of Carboxamides Substituted by Electron-Withdrawing Groups1. J Org Chem 2004; 69:5947-65. [PMID: 15373479 DOI: 10.1021/jo040196b] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The gas-phase acidities DeltaG degrees (acid) of some 20 amides/enols of amides RNHCOCHYY'/RNHC(OH)=CYY' [R = Ph, i-Pr; Y, Y' = CO(2)R', CO(2)R' ', or CN, CO(2)R', R', R' ' = Me, CH(2)CF(3), CH(CF(3))(2)], the N-Ph and N-Pr-i amides of Meldrum's acid, 1,3-cyclopentanedione, dimedone, and 1,3-indanedione, and some N-p-BrC(6)H(4) derivatives and of nine CH(2)YY' (Y, Y' = CN, CO(2)R', CO(2)R' '), including the cyclic carbon acids listed above, were determined by ICR. The acidities were calculated at the B3LYP/6-31+G//B3LYP/6-31+G level for both the enol and the amide species or for the carbon acid and the enol on the CO in the CH(2)YY' series. For 12 of the compounds, calculations were also conducted with the larger base sets 6-311+G and G-311+G. The DeltaG degrees (acid) values changed from 341.3 kcal/mol for CH(2)(CO(2)Me)(2) to 301.0 kcal/mol for PhNHC(OH)=C(CN)CH(CF(3))(2). The acidities increased for combinations of Y and Y' based on the order CO(2)Me < CO(2)CH(2)CF(3) < CN, CO(2)CH(CF(3))(2) for a single group and reflect the increased electron-withdrawal ability of Y,Y' coupled with the ability to achieve planarity of the crowded anion. The acidities of corresponding YY'-substituted systems follow the order N-Ph enols > N-Pr-i enols >> CH(2)YY'. Better linear relationships between DeltaG degrees (acid) values calculated for the enols and the observed values than those for the values calculated for the amides suggest that the ionization site is the enolic O-H of most of the noncyclic trisubstituted methanes. The experimental DeltaG degrees (acid) value for Meldrum's acid matches the recently reported calculated value. The calculated structures and natural charges of all species are given, and the changes occurring in them on ionization are discussed. Correlations between the DeltaG degrees (acid) values and the pK(enol) values, which are linear for the trisubstituted methanes, excluding YY' = (CN)(2) and nonlinear for the CH(2)YY' systems, are discussed.
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Affiliation(s)
- Masaaki Mishima
- Institute for Material Chemistry and Engineering, Kyushu University, 6-10-1 Hakozaki, Higashi-ku, Fukuoka 812-8581, Japan
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Kleinpeter E, Klod S, Rudorf WD. Electronic State of Push−Pull Alkenes: An Experimental Dynamic NMR and Theoretical ab Initio MO Study. J Org Chem 2004; 69:4317-29. [PMID: 15202885 DOI: 10.1021/jo0496345] [Citation(s) in RCA: 128] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The (1)H and (13)C NMR spectra of a number of push-pull alkenes were recorded and the (13)C chemical shifts calculated employing the GIAO perturbation method. Of the various levels of theory tried, MP2 calculations with a triple-zeta-valence basis set were found to be the most effective for providing reliable results. The effect of the solvent was also considered but only by single-point calculations. Generally, the agreement between the experimental and theoretically calculated (13)C chemical shifts was good with only the carbons of the carbonyl, thiocarbonyl, and cyano groups deviating significantly. The substituents on the different sides of the central C=C partial double bond were classified qualitatively with respect to their donor (S,S < S,N < N,N) and acceptor properties (C identical with N < C=O < C=S) and according to the ring size on the donor side (6 < 7 < 5). The geometries of both the ground (GS) and transition states (TS) of the restricted rotation about the central C=C partial double bond were also calculated at the HF and MP2 levels of theory and the free energy differences compared with the barriers to rotation determined experimentally by dynamic NMR spectroscopy. Structural differences between the various push-pull alkenes were reproduced well, but the barriers to rotation were generally overestimated theoretically. Nevertheless, by correlating the barriers to rotation and the length of the central C=C partial double bonds, the push-pull alkenes could be classified with respect to the amount of hydrogen bonding present, the extent of donor-acceptor interactions (the push-pull effect), and the level of steric hindrance within the molecules. Finally, by means of NBO analysis of a set of model push-pull alkenes (acceptors: -C identical with N, -CH=O, and -CH=S; donors: S, O, and NH), the occupation numbers of the bonding pi orbitals of the central C=C partial double bond were shown to quantitatively describe the acceptor powers of the substituents and the corresponding occupation numbers of the antibonding pi orbital the donor powers of the substituents. Thus, for the first time an estimation of both the acceptor and the donor properties of the substituents attached to the push-pull double bond have been separately quantified. Furthermore, both the balance between strong donor/weak acceptor substituents (and vice versa) and the additional influences on the barriers to rotation (hydrogen bonding and steric hindrance in the GSs and TSs) could be differentiated.
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Affiliation(s)
- Erich Kleinpeter
- Universität Potsdam, Chemisches Institut, PO Box 60 15 53, D-14415 Potsdam, Germany.
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Basheer A, Rappoport Z. Enols of Amides Activated by the 2,2,2-Trichloroethoxycarbonyl Group. J Org Chem 2004; 69:1151-60. [PMID: 14961664 DOI: 10.1021/jo030266z] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Reaction of isocyanates XNCO (X = Ar, i-Pr, t-Bu) with CH(2)(Y)CO(2)CH(2)CCl(3) (Y = CO(2)Me, CO(2)CH(2)CCl(3), CN) gave 15 amides XNHCOCH(Y)CO(2)CH(2)CCl(3) (6) or enols of amides XNHC(OH)=C(Y)CO(2)CH(2)CCl(3) (5) systems. The amide/enol ratios in solution depend strongly on the substituent Y and the solvent and mildly on the substituent X. The percentage of enol for group Y increases according to Y = CN > CO(2)CH(2)CCl(3) > CO(2)Me and decreases with the solvent according to CCl(4) > C(6)D(6) > CDCl(3) > THF-d(8) > CD(3)CN > DMSO-d(6). With the most acidic systems (Y = CN) amide/enol exchange is observed in moderately polar solvents and ionization to the conjugate base is observed in DMSO-d(6). The solid-state structure of the compound with Y = CN, X = i-Pr was found to be that of the enol. The reasons for the stability of the enols were discussed in terms of polar and resonance effects. Intramolecular hydrogen bonds result in a very low delta(OH) and contribute to the stability of the enols and are responsible for the higher percentage of the E-isomers when Y = CO(2)Me and the Z-isomers when Y = CN. The differences in delta(OH), delta(NH), K(enol), and E/Z enol ratios from the analogues with CF(3) instead of CCl(3) are discussed.
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Affiliation(s)
- Ahmad Basheer
- Department of Organic Chemistry, The Hebrew University, Jerusalem 91904, Israel
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Malamidou-Xenikaki E, Spyroudis S, Tsanakopoulou M. Studies on the reactivity of aryliodonium ylides of 2-hydroxy-1,4-naphthoquinone: reactions with amines. J Org Chem 2003; 68:5627-31. [PMID: 12839455 DOI: 10.1021/jo0343679] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Aryliodonium ylides of 2-hydroxy-1,4-naphthoquinone react with amines in refluxing dichloromethane to afford good yields of indanedione 2-carboxamides 5, through a ring-contraction and alpha,alpha'-dioxoketene formation reaction. These amides exist in solution in an unusual enol-amide form. In contrast, the same reactants in a copper-catalyzed reaction afford arylamines and 3-iodo-4-hydroxy-1,2-naphthoquinone.
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Affiliation(s)
- Elizabeth Malamidou-Xenikaki
- Laboratory of Organic Chemistry, Department of Chemistry, University of Thessaloniki, Thessaloniki 54124, Greece
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Lei YX, Casarini D, Cerioni G, Rappoport Z. Stable enols of amides ArNHC(OH)=C(CN)CO(2)R. E/Z enols, equilibria with the amides, solvent effects, and hydrogen bonding. J Org Chem 2003; 68:947-59. [PMID: 12558420 DOI: 10.1021/jo020464a] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The structures of anilido cyano(fluoroalkoxycarbonyl)methanes ArNHCOCH(CN)CO(2)R, where R = CH(2)CF(3) or CH(CF(3))(2), Ar = p-XC(6)H(4), and X = MeO, Me, H, or Br, were investigated. In the solid state, all exist as the enols ArNHC(OH)=C(CN)CO(2)R 7 (R = CH(2)CF(3)) and 9 (R = CH(CF(3))(2)) with cis arrangement of the hydrogen-bonded ROC=O.HO moiety and a long C1=C2 bond. The product composition in solution is solvent dependent. In CDCl(3) solution, only a single enol is observed, whereas in THF-d(8) and CD(3)CN, two enols (E and Z) are the major products, and the amide is the minor product or not observed at all (K(Enol) 1.04-9 (CD(3)CN, 298 K) and 3 to >/=100 (THF, 300 K)). The percentage of the amide and the Z-enol increase upon an increase in temperature. In all solvents, the percent enol is higher for 9 than for 7. In CD(3)CN, more enol is observed when the aryl group is more electron-donating. The spectra in DMSO-d(6) and DMF-d(7) indicate the presence of mostly a single species, whose spectra do not change on addition of a base and is ascribed to the anion of the ionized carbon acid. Comparison with systems where the CN is replaced by a CO(2)R group (R = CH(2)CF(3), CH(CF(3))(2)) shows a higher percentage of enol for the CN-substituted system. Intramolecular (to CO(2)R) and intermolecular hydrogen bonds determine, to a significant extent, the stability of the enols, their Z/E ratios (e.g., Z/E (THF, 240 K) = 3.2-4.0 (7) and 0.9-1.3 (9)), and their delta(OH) in the (1)H spectra. The interconversion of Z- and E-enol by rotation around the C=C bond was studied by DNMR, and DeltaG() values of >/=15.3 and 14.1 +/- 0.4 kcal/mol for Z-7 and Z-9 were determined. Features of the NMR spectra of the enols and their anions are discussed.
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Affiliation(s)
- Yi Xiong Lei
- Department of Organic Chemistry, The Hebrew University, Jerusalem 91904, Israel
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Rochlin E, Rappoport Z. Stable simple enols. Resolution of chiral 1-[9'-(2'-fluoroanthryl)]-2,2-dimesitylethenol. A different racemization mechanism for the enol and its acetate. J Org Chem 2003; 68:216-26. [PMID: 12530843 DOI: 10.1021/jo020497q] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Chiral 1-[9'-(2'-methoxyanthryl)]-2,2-dimesitylethenol (2), 1-[9'-(2'-fluoroanthryl)]-2,2-dimesitylethenol (3), and 1-[9'-(2'-fluoroanthryl)]-2,2- dimesitylvinyl acetate (4) were synthesized and their DNMR behavior in C6D5NO2 was studied. 3 and 4 were resolved on an amylose tris(3,5-dimethylphenylcarbamate) HPLC column to their enantiomers. Acetate 4 racemizes slowly in solution with DeltaG(e)(++), DeltaH(e)(++), and DeltaS(e)(++) values of 26.2, 27.6 kcal mol(-)(1), and 4.3 eu, respectively, as expected for a rotational betabeta'-2-ring flip process in a vinyl propeller and the racemization is unaffected by added TFA, Et3N, and EtOD. Although 3 racemizes almost 350 times faster, the racemization is catalyzed by TFA and shows bell-shape catalysis by Et3N and a KIE in a partially deuteriated solvent. From this and the DNMR data, it is concluded that 3 does not racemize via a rotational betabeta'-2-ring flip. Five nonflip routes are discussed for the racemization of 3, and it is concluded that only the one initiated by protonation at C1 does not contradict the experimental data. By analogy with the E/Z isomerization of the structurally related 2-(m-methoxymesityl)-1,2-dimesitylethenol 17, it is suggested that in the absence of added catalyst one or more enol molecule(s) catalyze the enantiomerization of another one. Only partial resolution was achieved for 2 and from the similarity of its behavior with that of 3, it is suggested that it racemizes by the same mechanism.
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Affiliation(s)
- Elimelech Rochlin
- Department of Organic Chemistry, The Hebrew University, Jerusalem 91904, Israel
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Lei YX, Casarini D, Cerioni G, Rappoport Z. N-Isopropyl enols of carboxylic acid amides. J PHYS ORG CHEM 2003. [DOI: 10.1002/poc.629] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Abstract
The reaction of 10 carboxamides activated by two beta-electron-withdrawing groups, which mostly exist completely or partially in their enol forms, with diazomethane was investigated. The main outcome is the diversity of reactions observed. With the most acidic enols 3-7, activated by at least one trifluoroethoxycarbonyl group or a cyano group, O-methylation or O,N-dimethylation takes place. With beta-dimethoxycarbonyl-activated systems 5 and 8, the C-methylation product of the amide form was one of the products. With a Meldrum's acid anilide enol 2, a cleavage took place leading to the C-alkylated imine having a CH(CO(2)Me)(2) group. Exchange of one 2,2,2-trifluoroethoxycarbonyl by a methoxycarbonyl in the C,N-dimethylation product of Me(2)CHNHC(OH)[double bond]C(CO(2)CH(2)CF(3))(2) 4 took place. The 2-anilido-1,3-cyclopentanedione 10 was methylated on a ring carbonyl while the enol of the 1,3-indanedione analogue 11 reacted with three diazomethane molecules and underwent a ring expansion and O-methylation to the 3-anilido-1,4-dimethoxynaphthalene. It is suggested that the reaction initiates by protonation of the diazomethane by the enol and an approximate qualitative relationship exists between the acidity of the enol and K(enol) and the regioselectivity of the reaction.
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Affiliation(s)
- Yi Xiong Lei
- Department of Organic Chemistry, The Hebrew University, Jerusalem 91904, Israel
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