Relevant bibliographies by topics / Positional isomers

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  1. Journal articles
  2. Dissertations / Theses
  3. Book chapters
  4. Conference papers

Academic literature on the topic 'Positional isomers'

Author: Grafiati
Published: 4 June 2021
Last updated: 1 February 2022

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Journal articles on the topic "Positional isomers"

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Poriel, Cyril, and Joëlle Rault-Berthelot. "Dihydroindenofluorene Positional Isomers." Accounts of Chemical Research 51, no. 8 (July 18, 2018): 1818–30. http://dx.doi.org/10.1021/acs.accounts.8b00210.

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Anderson, Derrick R., Pavlo V. Solntsev, Hannah M. Rhoda, and Victor N. Nemykin. "How big is big? Separation by conventional methods, X-ray and electronic structures of positional isomers of bis-tert-butylisocyano adduct of 2(3),9(10),16(17),23(24)-tetrachloro-3(2),10(9),17(16),24(23)-tetra(2,6-di-iso-propylphenoxy)-phthalocyaninato iron(II) complex." Journal of Porphyrins and Phthalocyanines 20, no. 01n04 (January 2016): 337–51. http://dx.doi.org/10.1142/s1088424616500164.

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A presence of bulky 2,6-di-iso-propylphenoxy groups in bis-tert-butylisocyano adduct of 2(3),9(10),16(17),23(24)-tetrachloro-3(2),10(9),17(16),24(23)-tetra(2,6-di-iso-propylphenoxy)-phthalocyaninato iron(II) complex allows separation of two individual positional isomers and a mixture of the remaining two isomers using conventional chromatography. X-ray structures of “[Formula: see text]” and “[Formula: see text]” isomers were confimed by X-ray crystallography. Density functional theory (DFT) and time-dependent DFT (TDDFT) calculations of each individual positional isomer allowed insight into their electronic structures and vertical excitation energies, which were correlated with the experimental UV-vis and MCD spectra.
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Cisterna, Jonathan, Catherine Araneda, Pilar Narea, Alejandro Cárdenas, Jaime Llanos, and Iván Brito. "The Positional Isomeric Effect on the Structural Diversity of Cd(II) Coordination Polymers, Using Flexible Positional Isomeric Ligands Containing Pyridyl, Triazole, and Carboxylate Fragments." Molecules 23, no. 10 (October 14, 2018): 2634. http://dx.doi.org/10.3390/molecules23102634.

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To systematically investigate the influence of the positional isomeric effect on the structures of polymer complexes, we prepared two new polymers containing the two positional isomers ethyl 5-methyl-1-(pyridin-3-yl)-1H-1,2,3-triazole-3-carboxylate (L1) and ethyl-5-methyl-1-(pyridin-3-yl)-1H-1,2,3-triazole-4-carboxylate (L2), as well as Cd(II) ions. The structures of the metal–organic frameworks were determined by a single crystal XRD analysis. The compound [Cd(L1)2·4H2O] (1), is a hydrogen bond-induced coordination polymer, whereas the compound [Cd(L2)4·5H2O]n (2) is a three-dimensional (3-D) coordination polymer. Their structures and properties are tuned by the variable N-donor positions of the ligand isomers. This work indicates that the isomeric effect of the ligand isomers plays an important role in the construction of the Cd(II) complexes. In addition, the thermal and luminescent properties are reported in detail.
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Vasilkova, N. O., M. Ju Borisova, N. A. Jurasov, and A. P. Krivenko. "Reaggregation Positional Isomers Tetrazologeksahidroquinazoline." Chemistry. Biology. Ecology 16, no. 1 (March 18, 2016): 5–8. http://dx.doi.org/10.18500/1816-9775-2016-16-1-5-8.

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Kucherenko, T. T., A. V. Zadorozhny, and V. A. Kovtunenko. "Positional isomers of thienopyrimidinones." Chemistry of Heterocyclic Compounds 44, no. 6 (June 2008): 750–58. http://dx.doi.org/10.1007/s10593-008-0100-y.

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Chen, Fengli, Dongjie Bai, Donghao Jiang, Yao Wang, and Yabing He. "A comparative study of C2H2 adsorption properties in five isomeric copper-based MOFs based on naphthalene-derived diisophthalates." Dalton Transactions 46, no. 34 (2017): 11469–78. http://dx.doi.org/10.1039/c7dt02290e.

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Bailey, T. R., G. D. Diana, T. L. Draper, and D. C. Pevear. "Acetylfurans as Bio-Isosteres for 3-Methylisoxazole. The Effect of Acetylfuran Positional Isomers on Antirhinoviral Activity." Antiviral Chemistry and Chemotherapy 7, no. 1 (February 1996): 46–52. http://dx.doi.org/10.1177/095632029600700108.

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A panel of four isomeric acetylfuran analogues of disoxaril were prepared. Using a 96-well tissue culture inhibitory dose assay (TCID), these acetylfuran isomers were screened against 15 rhinovirus serotypes. Comparison of the results obtained suggested that antiviral activity was related to hydrogen bond participation by the carbonyl oxygen within the viral pocket. Modelling acetylfuran conformations using an X-ray crystal structure template of 1 in HRV-14 demonstrates that three of the four isomers can adopt the desired conformation for this hydrogen bonding, and the fourth isomer 15 is prohibited by steric constraints from achieving the necessary conformation. These observations are consistent with the hypothesis that broad-spectrum antirhinoviral activity may require a hydrogen bond acceptor at that region of the inhibitor.
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Völker, Plum, Gindikin, and Breslauer. "Dynamic DNA Energy Landscapes and Substrate Complexity in Triplet Repeat Expansion and DNA Repair." Biomolecules 9, no. 11 (November 6, 2019): 709. http://dx.doi.org/10.3390/biom9110709.

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DNA repeat domains implicated in DNA expansion diseases exhibit complex conformational and energy landscapes that impact biological outcomes. These landscapes include ensembles of entropically driven positional interchanges between isoenergetic, isomeric looped states referred to as rollamers. Here, we present evidence for the position-dependent impact on repeat DNA energy landscapes of an oxidative lesion (8oxodG) and of an abasic site analogue (tetrahydrofuran, F), the universal intermediate in base excision repair (BER). We demonstrate that these lesions modulate repeat bulge loop distributions within the wider dynamic rollamer triplet repeat landscapes. We showed that the presence of a lesion disrupts the energy degeneracy of the rollameric positional isomers. This lesion-induced disruption leads to the redistribution of loop isomers within the repeat loop rollamer ensemble, favoring those rollameric isomers where the lesion is positioned to be energetically least disruptive. These dynamic ensembles create a highly complex energy/conformational landscape of potential BER enzyme substrates to select for processing or to inhibit processing. We discuss the implications of such lesion-induced alterations in repeat DNA energy landscapes in the context of potential BER repair outcomes, thereby providing a biophysical basis for the intriguing in vivo observation of a linkage between pathogenic triplet repeat expansion and DNA repair.
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Bałczewski, Piotr, Joanna Skalik, Paweł Uznański, Dariusz Guziejewski, and Witold Ciesielski. "Use of isomeric, aromatic dialdehydes in the synthesis of photoactive, positional isomers of higher analogs of o-bromo(hetero)acenaldehydes." RSC Advances 5, no. 31 (2015): 24700–24704. http://dx.doi.org/10.1039/c4ra14071k.

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A series of photoresistant, positional isomers of o-bromo(hetero)acenaldehydes containing RO-Ar and bifunctional ortho-CHO/Br structural motifs, is available in the peculiar Friedel–Crafts modification, using isomeric aromatic o,o-dibromodialdehydes.
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Delmonte, Pierluigi, Martin P. Yurawecz, Magdi M. Mossoba, Cristina Cruz-Hernandez, and John K. G. Kramer. "Improved Identification of Conjugated Linoleic Acid Isomers Using Silver-Ion HPLC Separations." Journal of AOAC INTERNATIONAL 87, no. 2 (March 1, 2004): 563–68. http://dx.doi.org/10.1093/jaoac/87.2.563.

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Abstract Silver-ion high-performance liquid chromatography (Ag+-HPLC) has been shown to be effective in the resolution of most of the isomers of conjugated octadecadienoic acids (18:2), also known as conjugated linoleic acid (CLA). The CLA isomers identified in natural fats from ruminants are a mixture of numerous positional and geometric isomers from 7,9- to 12,14–18:2. Ag+-HPLC separates both geometric (trans,trans < cis/trans < cis,cis) and positional CLA isomers using the mobile phase hexane/acetonitrile (99.9:0.1). The elution volumes for the CLA isomers were not only affected by the concentration of acetonitrile (in the prepared mobile phase) but also with successive runs during the day using a prepared mobile phase batch, due to the partial solubility of acetonitrile in hexane. However, this drift does not affect the relative resolution of the CLA isomers. The addition of diethyl ether to the mobile phase partly stabilizes the solvent mixture. In order to facilitate the interpretation of Ag-+HPLC chromatograms, the relative retention volumes (RRV) were calculated for each CLA isomer. Toluene was added to all the test portions and served as an estimator of dead volume, whereas the elution of the ubiquitous 9c,11t-CLA isomer was chosen as unity (1.00). Expressing the elution of all the CLA isomers as their RRV greatly helped to standardize each CLA isomer, resulting in relatively small coefficients of variation (% CV) for the trans,trans (<1.5%) and cis/trans (<0.5%) CLA isomers. The identification of the CLA isomers was further facilitated by synthesis of authentic CLA isomers. All the geometric CLA fatty acid methyl esters (FAME) from positions 6,8- to 13,15-CLA were commercially available or synthesized by a combination of partial hydrazine reduction of known polyunsaturated fatty acids followed by alkali isomerization, isolation of products, and further iodine-catalyzed geometric isomerization. Based on expressing the elution volume as RRV and the availability of the synthetic CLA isomers, a unique reversal of the elution order of the c/t CLA isomers was found. It is also proposed that the retention times of CLA isomers by gas chromatography (GC) should be expressed as their relative retention times (RRT) relative to methyl γ-linoleneate. The availability of CLA reference materials and the application of RRV and RRT to Ag+-HPLC and GC separations, respectively, will greatly improve in the identifications of CLA isomers.
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Dissertations / Theses on the topic "Positional isomers"

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Van, Zyl Etiene Francois. "The Synthesis and analysis of methaqualone and some positional structural isomers therof." Pretoria : [s.n.], 2001. http://upetd.up.ac.za/thesis/available/etd-11232005-150329/.

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Webborn, P. J. H. "Positional effects of the sulphate moiety on the biochemistry of tridecan sulphate isomers." Thesis, Bucks New University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376431.

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Richardson, Ashley E. "Hydrophilic interaction and micellar liquid chromatography approaches for the separation of aromatic carboxylic acid positional isomers plus ion exchange chromatography for the separation of sulfonated compounds." Miami University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=miami1511295591427557.

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Chintalapudi, Kavyasree. "Development of Reactive Nano-Electrospray Mass Spectrometry (nESI-MS) Platform for Studying Electro-Catalytic Reactions using Non-Inert Electrodes." The Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1619043596792908.

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Peltier, Jean-David. "Isomères de position d’indacénodithiophènes : synthèse, propriétés et applications en transistors organiques à effet de champ." Thesis, Rennes 1, 2017. http://www.theses.fr/2017REN1S138/document.

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Les transistors organiques à effet de champ (OFETs) dans lesquels le transport des charges se fait à travers un film mince de molécules organiques représentent une transformation de la technologie des transistors à effet de champ au regard de la technologie au silicium. Ils permettent notamment d’envisager le développement d’une électronique flexible à bas coût. Ce travail porte sur la synthèse, l’étude et l’utilisation en tant que couche active dans des OFETs de type n de couples d’isomères para- et méta-indacénodithiophènes (para- et méta-IDT) appauvris en électrons inédits. Une introduction aux OFETs de type n est tout d’abord présentée. Elle est suivie par la présentation de la synthèse des dérivés IDT et de l’analyse comparée de leurs propriétés physico-chimiques. La fabrication des OFETs, leur caractérisation et l’optimisation de leur architecture est enfin décrite, leurs performances montrant l’intérêt des IDTs pour les OFETs de type n. Différentes fonctionnalisations menant à des IDTs d’architecture 3π-2spiro sont également synthétisées afin d’étudier les propriétés intrinsèques de ces dérivés π-conjugués et d’envisager leur incorporation comme matrice hôte dans des diodes électrophosphorescentes organiques
Organic Field Effect Transistors (OFETs), in which the charge transport is carried through a thin film made of organic molecules represent a transformation of the FET technology regarding that based on Silicon. They offer in particular the possibility to manufacture low cost flexible electronics. This work is focused on the synthesis, the study and the use as active layer in n-type OFETs of novel, electron poor, couples of para- and meta-indacenodithiophenes isomers (para- and meta-IDT). First of all, an introduction to the field of n-type OFETs is presented, followed by the presentation of the synthesis of the IDT derivatives and the comparative analysis of their properties. Finally, the fabrication of the OFETs, their characterization and the optimization of their architecture is described. The performances recorded attest that these derivatives are of great interest for the n-type OFETs. Different 3π-2spiro IDT derivatives are also presented in order to study the IDTs intrinsic properties and to envisage their incorporation as host in phosphorescent organic light-emitting diodes
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Hsiao, Jung-Yi, and 蕭榮憶. "Application of caplillary electrophoresis to separate positional isomers and enantiomers." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/09179405923381634575.

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碩士
國立中央大學
化學研究所
94
Capillary electrophoresis (CE) is one of the most popular analytical techniques in separation of positional/structural isomers and chiral compounds, and also can be used to evaluate the binding constants and thermodynamic parameters of guest-host inclusion complex. The first part of this study is application of CE to simultaneously determine the apparent binding constants and thermodynamic parameters for six positional/structural naphthalene sulfonate derivatives with ��-cyclo- dextrin (��-CD). The change in electrophoretic mobilities were used to assess the binding constants by nonlinear regression and three different linear plots methods (named double reciprocal, x-reciprocal and y- reciprocal). The substituent group(s) attached to the naphthalene ring considerably affected the inclusion behaviors of these naphthalene sulfonate derivatives. The binding constant varies over almost one order of magnitude and a highly selective sequence is obtained between these guest model compounds. Naphthalenesulfonates with the substituent(s) at the 2-position(s) displayed stronger interaction with ��-CD, and gave well compatible results by these four plot methods. While at least one substituent was substituted into the 1-position of naphthalene showed the weak interaction or no interaction with ��-CD. Comparison to three linear regression methods, the non-linear regression method proves to be the most suitable for these determinations. Additionally, apparent binding constants for each structural isomer with ��-CD at several temperature, and thermodynamic parameters for binding were also calculated and discussed. The second part of this study is application of CE to separate two groups of chiral chlorinated pesticides (dichloroprop and mecoprop) in water samples with (2-hydroxypropyl)-��-cyclodextrin (HP-��-CD). The most effective separation conditions were to use 50 mM ammonium acetate with 15 mM HP-��-CD at pH 4.6. Determination of the apparent binding constants and thermodynamic parameters for these two chiral pesticides were also calculated. The use of solid-phase extraction (SPE) and salting-out effect for the off-line preconcentration of chiral pesticides is demonstrated in this study. Oasis HLB-SPE cartridge was used to reduce interferences and enhance the extraction of analytes from surface water samples. The most effective salting-out effect was 0.45 g NaOH and 1.0 mL acetonitrile in 2-mL of SPE extract. Significantly sensitive improvement was observed and more than 2000-fold enrichment was achieved. Recovery of the analytes in various spiked water samples was up to 68% with RSD less than 13%.
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Chen, Tsan Ming, and 陳燦明. "Simultaneous separation and identification of geometrical and positional carotenoid isomers." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/88612951426085477487.

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Van, Zyl Etienne Francois. "The Synthesis and analysis of methaqualone and some positional structural isomers thereof." Diss., 2002. http://hdl.handle.net/2263/29713.

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An extensive review of the reported synthesis of methaqualone (2-methyl-3-ο-tolyl-4(3H)-quinazolinone) and some positional and structural isomers of methaqualone is given. A detailed summary of the synthetic routes reviewed is given as an appendix. Methaqualone, four previously reported, and seven until hereto unreported isomers of methaqualone were prepared using a modified, known synthetic route for quinazolinones. The modified route allowed for the rapid laboratory scale preparation of the desired quinazolinones in high yields. Melting points are given. The prepared compounds were characterized using various organic analytical techniques. NMR and IR was found to be the most specific single techniques for the effectively and unequivocally differentiation between the studied compounds. The most convenient, and equally specific, differentiation was achieved using coupled gas-liquid chromatography. The thin-layer chromatography and liquid chromatography systems evaluated proved of no value in differentiating the thirteen isomers.
Dissertation (MSc Applied Sciences (Chemistry))--University of Pretoria, 2006.
Chemistry
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Kao, Wei-hung, and 高偉紘. "Separation of Positional Mono-PEGylated Teriparatide Isomers Using Reverse-Phased Chromatography Assisted by Solubility Parameter Calculation." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/49558201281915593103.

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碩士
國立中央大學
化學工程與材料工程學系
101
Teriparatide, a peptide drug for treating to osteoporosis by once-daily injection, is the 1-34 segment of recombinant human parathyroid hormone. However, Teriparatide is proteolytically instable in human serum resulting in short circulation half-life (less than 1 hour). Therefore, conjugation with polyethylene glycol (PEGylation) to Teriparatide may shield it from proteolysis to prolong the circulation half-life. For the PEGylated Teriparatide, the positional isomers are usually formed with random PEGylation. We obtained the Nter-PEGylated and K13-PEGylated Teriparatide while the synthesis conditions using pH 6.0 and pH8.0 phosphate buffer, respectively. In this investigation, we intended to directly separate the isomers by tuning mobile phase pH in reversed-phase chromatography (RPC) operation. The results showed that the baseline separation of two isomers can be achieved by tuning the pH value of mobile phase from 7.0 to 9.0, and Nter-PEGylated Teriparatide is much retained in RPC. Form the solubility parameter measurement, we examined that the key factor for the separation of these two isomers is the polarity difference rather than hydrogen bonding or dispersion force. From the circular dichroism measurement, the K13- PEGylated Teriparatide with higher helixity shows less retained in RPC. The results are coherent with our previously proposed structure-retention relationships for peptide isomer retention prediction in RPC.
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Huang, Yi-Hsuan, and 黃亦萱. "Studies on the Mechano- and Vapo-chromism and Mechanofluoromemory of Positional Isomers of Di-pentiptycenyl Anthracenes." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/yuayzm.

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碩士
國立臺灣大學
化學研究所
105
Recently, we found that when a common planar chromophore like anthracene is substituted with the pentiptycenyl groups the resulting compound has the mechanofluorochromic (MFC), vapofluorochromic (VFC) and mechanofluorochromy (MFM) properties. We believe that the bulky pentitpycene groups prevent strong intermolecular interactions, which tend to make the system polymorphic and switchable by external mechano-stimuli. To further understand the mechanism of this system, we have investigated its position isomers, including 1,4-, 1,5-, 1,8- and 2,6- dipentiptcenylanthracene. The fluorescence spectra and time-dependent emission intensity were measured to compare their MFC and VFC properties by powder X-ray diffraction, scanning electron microscopy, transmission electron microscopy.
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Book chapters on the topic "Positional isomers"

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Ishikawa, Haruo, Kosaku Ishimi, and Keiichi Okajima. "Separation of Positional Isomers by Combined Use of Enzymatic Hydrolysis and Extraction." In Biochemical Engineering for 2001, 121–23. Tokyo: Springer Japan, 1992. http://dx.doi.org/10.1007/978-4-431-68180-9_31.

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Monkarsh, Seth P., Cheryl Spence, Jill E. Porter, Alicia Palleroni, Carlo Nalin, Perry Rosen, and Pascal Bailon. "Isolation of Positional Isomers of Mono-poly(ethylene glycol)ylated Interferon/α-2a and the Determination of Their Biochemical and Biological Characteristics." In ACS Symposium Series, 207–16. Washington, DC: American Chemical Society, 1997. http://dx.doi.org/10.1021/bk-1997-0680.ch015.

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Kuksis, Arnis. "ANALYSIS OF POSITIONAL ISOMERS OF GLYCEROLIPIDS BY NON-ENZYMATIC METHODS." In Advances in Lipid Methodology, 1–36. Elsevier, 2012. http://dx.doi.org/10.1533/9780857098009.1.

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Akoh, Casimir, Ki-Teak Lee, and Lydia Fomuso. "Synthesis of Positional Isomers of Structured Lipids with Lipases as Biocatalysts." In Structural Modified Food Fats, 46–72. AOCS Publishing, 1998. http://dx.doi.org/10.1201/9781439832103.ch3.

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Emken, E. A. "Absorption of Deuterium-Labeled cis- and trans-Octadecenoic Acid Positional Isomers in Man *." In Fat Absorption, 159–76. CRC Press, 2018. http://dx.doi.org/10.1201/9781351071994-5.

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Joarder, R. N. "The Molecular Conformations and Intermolecular Correlations in Positional Isomers 1- and 2- Propanols in Liquid State Through Neutron Diffraction." In Neutron Diffraction. InTech, 2012. http://dx.doi.org/10.5772/37488.

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"NMR Spectroscopic Differentiation of Diastereomeric Isomers Having Special Positions of Molecular Symmetry." In Symmetry, Spectroscopy, and Crystallography, 205–12. Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2015. http://dx.doi.org/10.1002/9783527684199.ch13.

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Glusker, Jenny Pickworth, and Kenneth N. Trueblood. "Anomalous scattering and absolute configuration." In Crystal Structure Analysis. Oxford University Press, 2010. http://dx.doi.org/10.1093/oso/9780199576340.003.0019.

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The concept of the carbon atom with four bonds extending in a tetrahedral fashion was put forward by van’t Hoff and Le Bel in 1874. It coincided with the realization that such an arrangement could be asymmetric if the four substituents were different, as shown in Figure 10.1a (van’t Hoff, 1874; Le Bel, 1874). Thus, for any compound containing one such asymmetric carbon atom, there are two isomers of opposite chirality (individually called enantiomers), for which threedimensional representations of their structural formulas are related by a mirror plane. Aqueous solutions of these enantiomers rotate the plane of polarized light in opposite directions. As discussed in Chapter 7, Pasteur showed that crystals of sodium ammonium tartrate had small asymmetrically located faces and that crystals with these so-called “hemihedral faces” rotated the plane of polarization of light clockwise, while crystals with similar faces in mirror-image positions rotated this plane of polarization counterclockwise. Thus the external form (that is, the morphology) of the crystals illustrated in Figure 10.1b was used to separate enantiomers (see Patterson and Buchanan, 1945). Pure enantiomers can only crystallize in noncentrosymmetric space groups unless both isomers are present. But even if the chemical formula and the three-dimensional structure of a molecule such as tartaric acid have been determined by standard X-ray diffraction methods, there is an ambiguity about the absolute configuration. Information about the absolute configuration is not contained in the diffraction pattern of the crystal as it is normally measured. Thus, although the substituents on the asymmetric carbon atoms have been identified, and even the detailed three-dimensional geometry of the molecule has been determined, it is not known which of the two enantiomers (mirror-image forms, analogous to those shown in Figure 10.1a) represents the three-dimensional structure of a particular individual molecule that has some distinguishing chiral property, such as the ability to rotate the plane of polarized light to the right. In other words, what is the absolute structure of the dextrorotatory form of the compound under study? A means of determining the absolute configurations of molecules was, however, provided by X-ray crystallographic studies.
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Poidevin, Robin Le. "Space and the Chiral Molecule." In Of Minds and Molecules. Oxford University Press, 2000. http://dx.doi.org/10.1093/oso/9780195128345.003.0016.

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According to classical stereochemistry, the molecules of some substances have doubles, in the sense of incongruent mirror-image counterparts. This is the phenomenon of optical isomerism, first identified 150 years ago by Pasteur. In some cases, the double occurs naturally; in others, it has to be artificially synthesized. These molecules thus share a geometrical feature with such familiar objects as our hands, and, indeed, it is this connection that gives the feature its technical name: chirality (from the Greek for hand, kheir). Instances of chirality in chemistry are numerous, especially in living things: examples of chiral molecules include adrenaline, glucose, and DNA. Optical isomerism is interesting, both historically—it played a crucial role in the emergence of structural chemistry and in the attempt to link chemistry with physics— and, I believe, philosophically. I should like to take this opportunity to revisit the scene of an earlier article of mine (Le Poidevin, 1994) in which I examined the implications optical isomerism has for a philosophical debate concerning the nature of space. In that article I argued that chirality in chemistry reinforces a conclusion that Graham Nerlich (1994), in a brilliant reconstruction of a famous argument of Kant’s, had derived from more visible instances of chirality: that we should be realists about the geometrical properties of space. I did not, however, want to follow Nerlich (and Kant) in drawing a more radical conclusion: that we should be realists about the existence of space. That may sound paradoxical, but it is possible (or so I thought) to regard space as a logical construction from its contents and still think of it, qua construction, as possessing certain intrinsic properties that we do not merely impose on it by convention. Since then, I have become more sympathetic to Nerlich’s position. Chirality is best understood by thinking of space as an entity in its own right. So chemistry has some lessons for the philosophy of space. But the pedagogical relation goes the other way, too: the philosophy of space has interesting implications for chemistry.
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Taber, Douglass. "Adventures in Alkaloid Synthesis: ( + )-α-Kainic Acid (Jung), 223AB (Ma), Pumiliotoxin 251F (Jamison), Spirotryprostatin B (Trost), (-)-Drupacine (Stoltz)." In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0058.

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Enantiomerically-pure natural amino acids can serve as starting materials for alkaloid synthesis. In his synthesis (J. Org. Chem. 2007, 72, 10114) of (-)-α-kainic acid 3, Kyung Woon Jung of the University of Southern California prepared the diazo sulfone 1 from (L)-glutamic acid. Rh-mediated intramolecular C-H insertion proceeded with the predicted high diastereoselectivity, to give the lactam 2, containing seven of the ten carbon atoms and two of the three stereogenic centers of (-)-α-kainic acid 3. The absolute configuration of the nitrogen ring system(s) can also be established by chiral catalysis. Dawei Ma of the Shanghai Institute of Organic Chemistry has developed (J. Am. Chem. Soc. 2007, 129, 9300) a chiral Cu catalyst that mediated the addition of alkynyl esters and ketones to the prochiral acylated pyridine 4 in high enantiomeric excess. The dihydro-pyridines (e.g. 5) so produced will be versatile starting materials both for alkaloid synthesis, as illustrated by the preparation of the Dendrobatid alkaloid 223AB 6, and for the production of pharmaceuticals. In his synthesis of the Dentrobatid alkaloid pumiliotoxin 251D 9, Timothy F. Jamison took (J. Org. Chem. 2007, 72, 7451) as his starting material another amino acid, proline. Ni-mediated cyclization of the epoxide 8 proceeded with high geometric and regiocontrol, to give 9. The chemistry to convert 7 into 8 with high diastereocontrol and without racemization is a substantial contribution that will have many other applications. In his synthesis (Organic Lett. 2007, 9, 2763) of spirotryprostatin B 12, Barry M. Trost of Stanford University also started with proline, which was readily elaborated to the oxindole 10. The question was, could the Pd-catalyzed decarboxylation of 10 be induced to provide specifically 11? Counting geometric isomers of the trisubstituted alkene, and allylic regioisomers, as well as diastereomers, there were sixteen possible products from this prenylation. Using chiral Pd control, the rearrangement proceeded with 14:1 regiocontrol, and 16:1 diasterocontrol. Oxidative cyclization of 11 then delivered spirotryprostatin B 12. The Cephalotaxus alkaloid (-)-drupacine 19 has five stereogenic centers, including four of the five positions on the cyclopentane ring.
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Conference papers on the topic "Positional isomers"

1

Gan, Zong Yuan, Ravinder Kodela, Satindra Goswami, Mitali Chattopadhyay, Daniel Boring, James A. Crowell, and Khosrow Kashfi. "Abstract 5560: All three positional isomers of acetyl salicylic acids are equally potent in inhibiting colon cancer cell growth: Differences in mode of COX inhibition." In Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL. American Association for Cancer Research, 2011. http://dx.doi.org/10.1158/1538-7445.am2011-5560.

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2

Eschbach, Erin K., Andrew C. MacKessack-Leitch, Federica Vannini, Ravinder Kodela, Mitali Chattopadhyay, and Khosrow Kashfi. "Abstract 4556: NOSH-aspirin is a potent inhibitor of colon cancer cell growth: effects of positional isomerism." In Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC. American Association for Cancer Research, 2013. http://dx.doi.org/10.1158/1538-7445.am2013-4556.

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3

Du, Yong, Guohui Hao, Rongjiao Zhao, and Zhi Hong. "Investigating the position isomerism effect of dihydroxybenzoic acid compounds by terahertz time-domain spectroscopy." In Photonics and Optoelectronics Meetings 2011, edited by Jianquan Yao, X. C. Zhang, Dapeng Yan, and Jinsong Liu. SPIE, 2012. http://dx.doi.org/10.1117/12.918851.

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