DOCSLIB.ORG

Crystal Engineering Rescues a Solution Organic Synthesis in a Cocrystallization That Confirms the Configuration of a Molecular Ladder

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Crystal Engineering Rescues a Solution Organic Synthesis in a Cocrystallization That Confirms the Configuration of a Molecular Ladder Crystal engineering rescues a solution organic synthesis in a cocrystallization that confirms the configuration of a molecular ladder Manza B. J. Atkinsona, S. V. Santhana Mariappana,b, Dejan-Krešimir Bučara, Jonas Baltrusaitisa, Tomislav Friščića, Naif G. Sinadaa, and Leonard R. MacGillivraya,1 aDepartment of Chemistry, University of Iowa, Iowa City, IA 52242-1294; and bCentral NMR Facility, University of Iowa, Iowa City, IA 52242-1294 Edited by Jack Halpern, University of Chicago, Chicago, IL, and approved May 19, 2011 (received for review March 19, 2011) Treatment of an achiral molecular ladder of C2h symmetry com- posed of five edge-sharing cyclobutane rings, or a [5]-ladderane, with acid results in cis-totrans-isomerization of end pyridyl groups. Solution NMR spectroscopy and quantum chemical calcula- tions support the isomerization to generate two diastereomers. The NMR data, however, could not lead to unambiguous configura- tional assignments of the two isomers. Single-crystal X-ray diffrac- tion was employed to determine each configuration. One isomer readily crystallized as a pure form and X-ray diffraction revealed Scheme 1 the molecule as being achiral based on Ci symmetry. The second isomer resisted crystallization under a variety of conditions. Con- 2 þ 2 sequently, a strategy based on a cocrystallization was developed assemblies for [ ] photocycloadditions that generate [3]- and [5]-ladderanes (12). Cocrystallization of 5-methoxyresorcinol to generate single crystals of the second isomer. Cocrystallization trans of the isomer with a carboxylic acid readily afforded single crystals (5-OMe-res) with either an all- -4-pyridyl-substituted 1,4- that confirmed a chiral ladderane based on C symmetry. The chiral butadiene or 1,6-hexatriene yielded assemblies of composition 2 2ðtemplateÞ · 2ðpolyeneÞ. UV-irradiation produced the corre- ladderane and acid self-assembled to generate a five-component n hydrogen-bonded complex that packs to form large solvent-filled sponding end-functionalized C2h-symmetric ladderane 4-pyr[ ]- homochiral channels of nanometer-scale dimensions. Whereas co- lad stereospecifically, in quantitative yield, and in gram amounts. The ladderanes we generate in the solid state are cumbersome to crystallizations are frequently applied to structure determinations make using conventional solution methods of organic synthesis. of proteins, our study represents the first application of a cocrys- Difficulties are evidenced by the fact that ladderanes lacking in- tallization to confirm the relative configuration of a small-molecule ternal functional groups, such as those in the natural products, diastereomer generated in a solution-phase organic synthesis. are rare, with exceptions being ladderanes derived from intramo- lecular reactions of cyclophanes (14, 15). Recent reports by Corey supramolecular synthesis ∣ solid-state reactivity ∣ hydrogen bonding and coworkers on the first total and enantioselective syntheses of ladderane lipids in the form of (Æ)-pentacycloanammoxic acid, rystal engineering involves the rational design of solids with as well as attempted syntheses from polyenes in solution and the Cpredictable and/or tunable properties (1, 2). During the past solid state, highlight these difficulties (19–21). two decades, crystal engineering has undergone remarkable In this paper, we report an application of a cocrystallization to growth with applications in areas such as catalysis (3), energy sto- determine the relative configuration of a chiral ladderane gener- rage (4), electronics (5, 6), and pharmaceutics (7, 8). A burgeon- ated in a solution-phase isomerization. Our interests lie in using ing area in the field of crystal engineering involves the design and ladderanes synthesized in the solid state as precursors to the – properties of cocrystals (7 11). Cocrystals are multicomponent natural lipids. During experiments to treat 4-pyr-[5]-lad with solids with organic compounds assembled in combination to form acid, the terminal pyridyl groups were determined to undergo a a crystalline solid with properties different than the individual cis-totrans-isomerization that generates two isomers. Multidi- components (9–11). A cocrystal typically consists of a target mensional solution NMR spectroscopy—a tool commonly used molecule crystallized with a second molecule, or cocrystal former to elucidate the structures of organic molecules—supported the (CCF), employed to influence properties of the target (e.g., isomerization, along with quantum chemical calculations, to solubility, conductivity). The CCF interacts with the target via produce two diastereomers; namely, achiral 1a and chiral 1b intermolecular forces (e.g., hydrogen bonding) that serve to unite (Scheme 2). The NMR data, however, could not be used to un- and hold the components together. ambiguously determine the relative configuration of each isomer In this context, we have described a cocrystal approach to owing to close structural similarities of the two molecules. synthesize [n]-ladderanes (where: n ¼ 3 or 5) in the solid state (12, 13). The [n]-ladderanes are rod-shaped molecules composed of n edge-fused cyclobutane rings that define a molecular equiva- Author contributions: M.B.J.A., S.V.S.M., D.-K.B., J.B., and L.R.M. designed research; M.B.J.A., S.V.S.M., D.-K.B., J.B., and N.G.S. performed research; M.B.J.A., S.V.S.M., D.-K.B., lent of a macroscopic ladder (14, 15) (Scheme 1). Ladderanes J.B., T.F., and L.R.M. analyzed data; and M.B.J.A. and L.R.M. wrote the paper. are promising building blocks in optoelectronics and have been The authors declare no conflict of interest. recently discovered as building blocks of natural products, being This article is a PNAS Direct Submission. present as lipids in anammox (anaerobic ammonium oxidizing) – Data deposition: The crystallography, atomic coordinates, and structure factors have been marine bacteria (16 18). The ladderane lipids serve a structural deposited in the Cambridge Structural Database, Cambridge Crystallographic Data Centre role of providing extraordinary rigidity to internal membrane (CCDC), Cambridge CB2 1EZ, United Kingdom (CSD reference nos. 768180 and 768181). components. More specifically, we have shown that a CCF based 1To whom correspondence should be addressed. E-mail: [email protected]. on 1,3-dihydroxybenzene, or resorcinol (res), acts as a template This article contains supporting information online at www.pnas.org/lookup/suppl/ to assemble polyenes via hydrogen bonds into supramolecular doi:10.1073/pnas.1104352108/-/DCSupplemental. 10974–10979 ∣ PNAS ∣ July 5, 2011 ∣ vol. 108 ∣ no. 27 www.pnas.org/cgi/doi/10.1073/pnas.1104352108 Downloaded by guest on September 23, 2021 are difficult to obtain and structure cannot be confirmed using spectroscopic methods alone. Results and Discussion Our study begins with achiral C2h-symmetric 4-pyr-[5]-lad, which is obtained using 5-OMe-res as a template. Treatment of a related rctt-monocyclobutane was reported (28) to result in a cis-totrans- isomerization of pyridyl groups to give the rtct-stereoisomer in quantitative yield. Our goal was to determine if treatment of 4-pyr-[5]-lad with acid could generate more complex ladderanes as products. When 4-pyr-[5]-lad, upon removal from the template, was reacted with glacial acetic acid (AcOH) for 12 h at 50 °C, a 1H NMR spectrum suggested that the ladderane underwent an iso- Scheme 2 merization (Fig. 1). An isomerization was evidenced by the dis- appearance of peaks of 4-pyr-[5]-lad and multiplication of the 1H resonances in the pyridyl (7.00–8.50 ppm) and polycyclobutyl Thus, to confirm the structures of the two ladderanes, we turned (2.40–4.50 ppm) regions (Fig. 1A). A 1H-1H COSY spectrum of to single-crystal X-ray diffraction. Moreover, whereas one isomer the reaction mixture revealed 12 groups of resonances in the poly- readily crystallized and was confirmed as achiral 1a, the second cyclobutyl region with two sets of six groups being of the same isomer resisted crystallization under a variety of conditions. To relative intensity and correlated as two separate J-coupling net- circumvent difficulties to obtain single crystals, we revisited prin- works (Fig. 1B). The two coupling networks suggested the reac- tion generated two isomers in a 1∶1 ratio. When the reaction was ciples of crystal engineering by employing a cocrystallization 1 (Scheme 3). Cocrystallizations are often used to determine struc- conducted at 25 °C, the H NMR spectrum was more complex tures of biomolecules (e.g., proteins) (22), yet applications to par- with additional resonances in both the pyridyl and polycyclobutyl SI Text allel problems involving small molecules have been less explored, regions ( ). Collectively, our observations are consistent with absolute structure determinations of steroids (23, 24) and, with the terminal 4-pyridyl groups of 4-pyr-[5]-lad undergoing an acid-catalyzed cis-totrans-isomerization that initially generated more recently, separations and structure determinations of natur- partially isomerized unsymmetrical ladderanes that converted to al products (25, 26) and a bicyclobutyl being the only examples two symmetrical isomers in equal amounts. (27). Here, a cocrystallization of the second isomer with 3,5-dini- In principle, a cis-totrans-conversion of the end groups of trobenzoic acid (3,5-DNBA) readily afforded single crystals that 4-pyr-[5]-lad can generate two stereoisomers. One isomer 1a enabled the relative configuration of chiral 1b to be confirmed. contains pyridyl groups that point in opposite directions at the The isomer 1b details a unique case wherein chirality of a ladder- top and bottom halves of the molecule. The isomer 1a is achiral, ane is generated from the dispositions of identical end substitu- being based on inversion symmetry (Ci symmetry). The second CHEMISTRY ents. The components of the cocrystal form a hydrogen-bonded complex that packs to give a homochiral solid with solvent-filled channels of nanometer-scale dimensions. We expect the cocrystal approach described here to be applicable to similar problems of structure determination in organic chemistry where single crystals Fig. 1. NMR spectra of reaction of 4-pyr-[5]-lad with AcOH.
Load more

Recommended publications
  • Manhattan, KS
    Acknowledgements General Chair Daniel A. Higgins Program Chair J. Vincent Ortiz Symposia Chairs Crystal Engineering – Supramolecular Chemistry Christer Aakeröy Drug Discovery and Bioorganic Chemistry Duy H. Hua Environmental Chemistry Larry E. Erickson Methods of Electronic Structure Theory J. Vincent Ortiz Nanostructured Materials and Air Quality Kenneth J. Klabunde Sol-Gel Chemistry Maryanne M. Collinson Undergraduate Research Stefan Kraft Treasurer Yasmin Patell Exposition Chair Earline Dikeman Undergraduate Program Janie Salmon Audio/Video Resources James R. Hodgson Program Book Ruth Hathaway Printing/Publicity Ellen Stauffer KSU Div. of Continuing Education Website KSU Div. of Continuing Education Program Book Art Jessa Talamentez KSU Div. of Continuing Education Midwest Award Leah O’Brien ACS Regional Meeting Planner John Michael Sophos Welcome to the 39th Midwest Regional Meeting of the American Chemical Society October 20-22, 2004 Manhattan Holiday Inn Holidome Manhattan, KS Hosted by the Kansas State University Section Local Sections of the Midwest Region Of the American Chemical Society Ames Iowa Kansas City Kansas State University Mark Twain Mo-Kan-Ok Nebraska Omaha Ozark Sioux Valley South Central Missouri Southern Illinois St. Louis University of Kansas University of Missouri University of Arkansas Wichita MWRM 2004 39th Midwest Regional Meeting October 20-22, 2004 Table of Contents Acknowledgements inside front cover Welcome 1 Local Sections of the Midwest Region 2 Table of Contents 3 Special Greeting Brad Everett, Mayor,
    [Show full text]
  • 51Th International Mendeleev Olympiad, 2017 Astana 1St Theoretical Tour Problems
    51th International Mendeleev Olympiad, 2017 Astana 1st theoretical tour Problems Problem 1 “I’ll be back” Terminator T-800 Paying tribute to my constant co-author Plastic pollution is defined as accumulation of plastic products in the environment producing a negative impact on animal and human habitats. This problem is among the most vital challenges facing humanity nowadays. Surprisingly, sometimes nature itself offers assistance, such as bioremediation. Thus, Japanese researchers have recently discovered that the bacterium Ideonella sakaiensis can use polyethylene terephthalate (PET), a polymer with an extremely high resistance towards biodegradation, as the major source of carbon and energy. O O O O n PET biodegradation involves two enzymatic steps catalyzed by hydrolases and leading to three low molecular weight (М<600 g/mole) aromatic products A, B, and C with the number of types of hydrogens of 2, 4, and 6, respectively. After penetration inside Ideonella sakaiensis cells, C is metabolized into А, which turns out to be the only source of carbon for the bacterium. 1. Show the chemical bonds (use arrows) in the PET formula that are cleaved in the process of its hydrolase-catalyzed biodegradation. 2. Draw all possible structures of A, B, and C, which are in agreement with the given data. A undergoes a three-step enzyme catalyzed metabolic transformation (all chemical equations): O 2 CO2 O2 O A A1 A2 X OH X + + + + A3 NADPH + H NADP NADP NADPH + H X is a functional group in A3, NADP+ and NADPH are oxidized and reduced co-enzyme forms, respectively. 3. Deduce the structural formula of A3 if its molar fractions of oxygen and hydrogen are equal and lower than that of carbon.
    [Show full text]
  • Polyacetylene: Myth and Reality
    materials Review Polyacetylene: Myth and Reality Bruce S. Hudson Department of Chemistry, Syracuse University, Syracuse, NY 13244-4100, USA; [email protected]; Tel.: +1-315-443-5805 Received: 31 December 2017; Accepted: 31 January 2018; Published: 6 February 2018 Abstract: Polyacetylene, the simplest and oldest of potentially conducting polymers, has never been made in a form that permits rigorous determination of its structure. Trans polyacetylene in its fully extended form will have a potential energy surface with two equivalent minima. It has been assumed that this results in bond length alternation. It is, rather, very likely that the zero-point energy is above the Peierls barrier. The experimental studies that purport to show bond alternation are reviewed and shown to be compromised by serious experimental inconsistencies or by the presence, for which there is considerable evidence, of finite chain polyenes. In this view, addition of dopants results in conductivity by facilitation of charge transport between finite polyenes. The double minimum potential that necessarily occurs for polyacetylene, if viewed as the result of elongation of finite 1 1 chains, originates from admixture of the 1 Ag ground electronic state with the 2 Ag excited electronic singlet state. This excitation is diradical (two electron) in character. The polyacetylene limit is an 1 equal admixture of these two Ag states making theory intractable for long chains. A method is outlined for preparation of high molecular weight polyacetylene with fully extended chains that are prevented from reacting with neighboring chains. Keywords: polyacetylene; double-minimum potential; Peierls barrier; zero-point level; cross-linking 1. Introduction/Background History Polyacetylene is selected for review because of its relative simplicity; the small periodic repeat permits polyacetylene to be treated by sophisticated computational methods.
    [Show full text]
  • Noah Burns CV 2019
    Noah Z. Burns, Ph.D. Curriculum Vitae Stanford University office: 335 Lokey Department of Chemistry phone: (650) 723-2961 333 Campus Drive [email protected] Stanford, CA 94305 burnschemistry.com APPOINTMENT Associate Professor 2019 Stanford University, Stanford CA Assistant Professor 2012–2019 Stanford University, Stanford CA EDUCATION AND TRAINING Postdoctoral Fellow (NIH) 2009–2012 Harvard University, Cambridge MA Advisor: Eric N. Jacobsen Doctor of Philosophy 2004–2009 The Scripps Research Institute, La Jolla CA Advisor: Phil S. Baran Thesis: Total Syntheses of Haouamine A Bachelor of Arts, Chemistry 2000–2004 Columbia University, New York NY Advisor: James L. Leighton AWARDS AND HONORS 2019 Eli Lilly Young Investigator Award 2019: NSF CAREER Award 2018: Kavli Fellow 2017: Dean's Award for First Years of Teaching at Stanford 2017: Amgen Young Investigator Award 2013–present: Stanford Terman Fellow 2012: Thieme Chemistry Journal Award 2009–2012: NIH NRSA Postdoctoral Fellow 2006–2008: ARCS Foundation Scholarship 2006: Roche Excellence in Chemistry Award 2005–2006: TSRI Dean’s Fellow 2004: Graduated Summa Cum Laude, Columbia University 2004: Phi Beta Kappa 2003: Barry M. Goldwater Scholarship 2002: NSF Summer Undergraduate Research Fellowship PEER-REVIEWED PUBLICATIONS INDEPENDENT CAREER Smith, M. W.; Falk, I. D.; Ikemoto, H.; Burns, N. Z. “A Convenient C–H Functionalization Platform for Pyrroloiminoquinone Alkaloid Synthesis,” Tetrahedron 2019, 75, 3366–3370. [Invited contribution in honor of Professor Ryan Shenvi, recipient of the 2019 Tetrahedron Young Investigator Award.] Landry, M. L.; McKenna, G. M.; Burns, N. Z. “Enantioselective Synthesis of Azamerone,” J. Am. Chem. Soc. 2019, 141, 2867–2871. Kearney, S. E. et al. “Canvass: A Crowd-Sourced, Natural-Product Screening Library for Exploring Biological Space,” ACS Central Science 2018, 4, 1727–1741.
    [Show full text]
  • Structural Identification of Ladderane and Other Membrane Lipids Of
    Structural identification of ladderane and other membrane lipids of planctomycetes capable of anaerobic ammonium oxidation (anammox) Jaap S. Sinninghe Damste´ 1, W. Irene C. Rijpstra1, Jan A. J. Geenevasen2, Marc Strous3 and Mike S. M. Jetten3 1 Royal Netherlands Institute for Sea Research (NIOZ), Department of Marine Biogeochemistry and Toxicology, Texel, the Netherlands 2 van ‘t Hoff Institute for Molecular Science (HIMS), University of Amsterdam, the Netherlands 3 Department of Microbiology, Institute of Water and Wetland Research, Radboud University Nijmegen, the Netherlands Keywords The membrane lipid composition of planctomycetes capable of the an- ether lipids; fatty acids; mass spectrometry; aerobic oxidation of ammonium (anammox), i.e. Candidatus ‘Brocadia mixed glycerol ester/ether lipids; NMR anammoxidans’ and Candidatus ‘Kuenenia stuttgartiensis’, was shown to be composed mainly of so-called ladderane lipids. These lipids are com- Correspondence J. S. Sinninghe Damste´ , Royal Netherlands prised of three to five linearly concatenated cyclobutane moieties with cis Institute for Sea Research (NIOZ), ring junctions, which occurred as fatty acids, fatty alcohols, alkyl glycerol Department of Marine Biogeochemistry and monoethers, dialkyl glycerol diethers and mixed glycerol ether ⁄ esters. The Toxicology, PO Box 59, 1790 AB Den Burg, highly strained ladderane moieties were thermally unstable, which resulted the Netherlands in breakdown during their analysis with GC. This was shown by isolation Fax: +31 222 319 674 of a thermal product of these ladderanes and subsequent analysis with Tel: +31 222 369 550 two-dimensional NMR techniques. Comprehensive MS and relative retent- E-mail: [email protected] ion time data for all the encountered ladderane membrane lipids is repor- (Received 26 May 2005, revised 23 June ted, allowing the identification of ladderanes in other bacterial cultures and 2005, accepted 1 July 2005) in the environment.
    [Show full text]
  • Short Chain Ladderanes: Oxic Biodegradation Products of Anammox Lipids
    UvA-DARE (Digital Academic Repository) Short chain ladderanes: oxic biodegradation products of anammox lipids Rush, D.; Jaeschke, A.; Hopmans, E.C.; Geenevasen, J.A.J.; Schouten, S.; Sinninghe Damsté, J.S. DOI 10.1016/j.gca.2011.01.013 Publication date 2011 Document Version Final published version Published in Geochimica et Cosmochimica Acta Link to publication Citation for published version (APA): Rush, D., Jaeschke, A., Hopmans, E. C., Geenevasen, J. A. J., Schouten, S., & Sinninghe Damsté, J. S. (2011). Short chain ladderanes: oxic biodegradation products of anammox lipids. Geochimica et Cosmochimica Acta, 75(6), 1662-1671. https://doi.org/10.1016/j.gca.2011.01.013 General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. UvA-DARE is a service provided by the library of the University of Amsterdam (https://dare.uva.nl) Download date:29 Sep 2021 Available online at www.sciencedirect.com Geochimica et Cosmochimica Acta 75 (2011) 1662–1671 www.elsevier.com/locate/gca Short chain ladderanes: Oxic biodegradation products of anammox lipids Darci Rush a,⇑, Andrea Jaeschke a,1, Ellen C.
    [Show full text]
  • On Anammox Activity at Low Temperature: Effect of Ladderane Composition, Process
    bioRxiv preprint doi: https://doi.org/10.1101/2019.12.15.873869; this version posted December 15, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission. 1 On anammox activity at low temperature: effect of ladderane composition, process 2 conditions and dominant anammox population 3 Kouba V1†, Hurkova K2, Navratilova K2, Vejmelkova D1, Benakova A1, Laureni M3, Vodickova P1,5, 4 Podzimek T5, Lipovova P5, van Niftrik L4, Hajslova J*2, van Loosdrecht MCM*3, Weissbrodt DG*3, 5 Bartacek J.*1 6 1 University of Chemistry and Technology Prague, Department of Water Technology and 7 Environmental Engineering, Technická 5, 166 28 Prague, Czechia 8 2 University of Chemistry and Technology Prague, Department of Food Analysis and Nutrition, 9 Technická 5, 166 28 Prague, Czechia 10 3 Delft University of Technology, Department of Biotechnology, Building 58, Van der Maasweg 9, 11 2629 HZ, Delft 12 4 Radboud University, Department of Microbiology, Institute for Water and Wetland Research, 13 1Heyendaalseweg 135, 6525 ED AJ Nijmegen, The Netherlands 14 5 University of Chemistry and Technology Prague, Department of Biochemistry and Microbiology, 15 Technická 5, 166 28 Prague, Czechia 16 *these co-authors contributed equally 17 †corresponding author, [email protected] 18 1 bioRxiv preprint doi: https://doi.org/10.1101/2019.12.15.873869; this version posted December 15, 2019. The copyright holder for this preprint (which was not certified by peer review) is the author/funder. All rights reserved. No reuse allowed without permission.
    [Show full text]
  • An Intracytoplasmic Compartment in Anammox Bacteria
    FEMS Microbiology Letters 233 (2004) 7–13 www.fems-microbiology.org MiniReview The anammoxosome: an intracytoplasmic compartment in anammox bacteria Laura A. van Niftrik a, John A. Fuerst b, Jaap S. Sinninghe Damste c, J. Gijs Kuenen a, Mike S.M. Jetten a,d, Marc Strous d,* a Department of Biotechnology, Delft University of Technology, Julianalaan 67, 2628 BC Delft, The Netherlands b Department of Microbiology and Parasitology, University of Queensland, Brisbane, Qld. 4072, Australia c Department of Marine Biogeochemistry and Toxicology, Royal Netherlands Institute for Sea Research (NIOZ), P.O. Box 59, 1790 AB Den Burg, The Netherlands d Department of Microbiology, University of Nijmegen, Toernooiveld 1, 6525 ED Nijmegen, The Netherlands Received 14 November 2003; received in revised form 26 January 2004; accepted 26 January 2004 First published online 15 February 2004 Abstract Anammox bacteria belong to the phylum Planctomycetes and perform anaerobic ammonium oxidation (anammox); they oxidize ammonium with nitrite as the electron acceptor to yield dinitrogen gas. The anammox reaction takes place inside the anam- moxosome: an intracytoplasmic compartment bounded by a single ladderane lipid-containing membrane. The anammox bacteria, first found in a wastewater treatment plant in The Netherlands, have the potential to remove ammonium from wastewater without the addition of organic carbon. Very recently anammox bacteria were also discovered in the Black Sea where they are responsible for 30–50% of the nitrogen consumption. This review will introduce different forms of intracytoplasmic membrane systems found in prokaryotes and discuss the com- partmentalization in anammox bacteria and its possible functional relation to catabolism and energy transduction.
    [Show full text]
  • 46Th National Organic Chemistry Symposium Poster Sessions Indiana University Alumni Hall & Solarium: IMU
    46th National Organic Chemistry Symposium Poster Sessions Indiana University Alumni Hall & Solarium: IMU For each night’s poster sessions, prizes for the two best graduate student/ post doc posters and one for the best undergraduate poster will be awarded. On Thursday we will also present three journal subscription prizes for superior posters from chosen from all poster sessions. Sunday: Poster Awards will be presented Monday morning by Jeffery Aubé (DOC Chair), University of North Carolina, Chapel Hill Monday: Poster Awards will be presented Tuesday morning by Silas Cook (NOS Local Co-Organizer), Indiana University—Bloomington Tuesday: Poster Awards will be presented Wednesday morning by Cristina Nevado (Senior Editor, ACS Central Science), University of Zürich Wednesday: Poster Awards will be presented Thursday morning by Paul Hanson (NOS Co- Executive Officer), University of Kansas Sunday, June 23, 2019 8-11PM Poster # Title Authors (Presenting*) Affiliation(s) Middle Aurone : Possible anti-fungal dyeing Shrijana Bhattarai*, Mary S- 1 Tennessee agent for fabric B. Farone, Scott T. Handy State University Panagiotis D. Alexakos*, Tetrazole-Mediated Ring Expansion: University of Mariana C. F. C. B. S- 2 A Mild Approach to Strained Illinois at Damião, Duncan J. Cyclooctynes Chicago Wardrop University of Site-Selective Copper-Catalyzed Sung-Eun Suh*, Si-Jie S- 3 Wisconsin– Azidation of Benzylic C–H Bonds Chen, Shannon S. Stahl Madison DevelopMent of Long Wavelength Gloria Ortiz*, Pei Liu, University of S- 4 Voltage Sensitive Dyes for IMaging Ashley Nensel, Evan W. California, Neuronal Activity Miller Berkeley Yaroslav D. Boyko*, University of Total Synthesis of Isomalabaricanes Christopher J. Huck, Illinois at S- 5 and a Blueprint for StereocheMically Alexander S.
    [Show full text]
  • Chemical Synthesis and Self-Assembly of a Ladderane
    Chemical Synthesis and Self-Assembly of a Ladderane Phospholipidf! Mercer, J. A. M.; Cohen, C. M.; Shuken, S. R.; Wagner, A. M.; Smith, M. W.; Moss, F. R.; Smith, M.D.;! Vahala, R.; Gonzalez-Martinez, A.; Boxer, S.G.; Burns, N. Z. J. Am. Chem. Soc. 2016, 138, 15854. O H H H H H O O Me N+ 3 O P O H H H H O- O H H H H H H H ! Michael Houghton Wipf Group 12/24/16 1 Michael Houghton@ Wipf Group Page 1 of 12 12/25/2016 General Uses and Types of Lipids - Lipids are used to provide and store energy, absorb vitamins, cell membrane and general cell health, signaling, and numerous other biological activities. OH H H H H H H H HO O Cholesterol Testosterone O HO Linoleic acid O O O O O O Triglceride (coconut oil) HO O Elaidic acid 2 Michael Houghton@ Wipf Group Page 2 of 12 12/25/2016 Ladderane Phospholipid is Found in Anammox Bacteria - Anammox- Anaerobic Ammonium Oxidizing - These bacteria convert ammonia and nitrite into dinitrogen and water - This process takes place in a unique organelle, the anammoxosome, which is composed of ~ 90 % ladderane phospholipds. - These densely packed phospholipds are believed to keep hydrazine and hydroxylamine waste products from damaging the rest of the cell. - There are five types of known anammox bacteria: Brocadia, Keunenia, Anammoxoglobus, Jettenia and Scalindua. - Anammox bacteria are used industrially to purify ammonia rich, contaminated water. - Purification difficulties have prohibited the isolation of pure material and useful quantities of material.
    [Show full text]
  • Mechanisms of the Thermal Cyclotrimerizations of Fluoro
    ARTICLE pubs.acs.org/JACS Mechanisms of the Thermal Cyclotrimerizations of Fluoro- and Chloroacetylenes: Density Functional Theory Investigation and Intermediate Trapping Experiments Zhong-Ke Yao and Zhi-Xiang Yu* Beijing National Laboratory for Molecular Sciences, Key Laboratory of Bioorganic Chemistry and Molecular Engineering of the Ministry of Education, College of Chemistry, Peking University, Beijing 100871, China bS Supporting Information ABSTRACT: Theoretical studies of the mechanisms of the thermal cyclotrimerization of fluoro- and chloroacetylenes, which were reported by Viehe and Ballester, respectively, were conducted with the aid of density functional theory calculations of the (U)B3LYP functional, indicating that the thermal cyclotrimerizations of fluoro- and chloroacetylenes involve tandem processes of regioselectively stepwise [2þ2] and stepwise [4þ2] cycloadditions. These tandem processes generate 1,2,6-trihalo-Dewar benzenes and 1,2,4-trihalo- Dewar benzenes, which then isomerize to the corresponding benzenes when heated. The rate-determining step of the cyclotri- merizations of haloacetylenes is the dimerization step involving open-shell singlet diradical transition states and intermediates. The substituent effects in the thermal cyclotrimerization of haloacetylenes have been rationalized using frontier molecular orbital theory. The higher reactivity of fluoroacetylenes compared to that of chloroacetylenes is due to the fact that fluoroacetylenes have lower singletÀtriplet gaps than chloroacetylenes and more easily undergo dimerization and cyclotrimerization. In this report, additional experiments were performed to verify the theoretical prediction about the cyclotrimerization of chloroacetylene and to trap the proposed 1,4-dichlorocyclobutadiene intermediate. Experiments revealed that the thermal reaction of phenylchloroacetylene at 110 °C gave 1,2,3-triphenyltrichlorobenzene and 1,2,4-triphenyltrichlorobenzene together with a tetramer, cis-1,2,5,6-tetrachloro- 3,4,7,8-tetraphenyltricyclo[4.2.0.02,5]octa-3,7-diene.
    [Show full text]
  • Scientific Publications of Roald Hoffmann May 2006
    Scientific Publications of Roald Hoffmann May 2006 BOOKS 1. The Conservation of Orbital Symmetry, R. B. Woodward and R. Hoffmann, Verlag Chemie and Academic Press, Weinheim and New York, 1970. 2. Solids and Surfaces: A Chemist's View of Bonding in Extended Structures, R. Hoffmann, VCH, New York, 1988. Translated into Russian by A. L. Tchougreev, Mir, Moscow, 1990. Translated into Chinese by H.-Y. Guo and Jing Li, J. China Chemical Industry Press, 1995. Translated into Japanese by Hiroshi Kobayashi, Youkoh Kaizu, and Toshiaki Enoki , Maruzen, 1993. ARTICLES 1. Heats of Formation of Hexacalcium Dialumino Ferrite and Dicalcium Ferrite, E. S. Newman and R. Hoffmann, J. Res. NBS, 56, 313 (1956). 2. Efficient Low-Level Counting System for C11, J. B. Cumming and R. Hoffmann, Rev. Sci. Inst., 29, 1104 (1958). 3. Theory of Polyhedral Molecules. I. Physical Factorizations of the Secular Equation, R. Hoffmann and W. N. Lipscomb, J. Chem. Phys., 36, 2179 (1962). 4. Theory of Polyhedral Molecules. II. A Crystal Field Model, R. Hoffmann and M. P. Gouterman, J. Chem. Phys., 36, 2189 (1962). 5. Theory of Polyhedral Molecules. III. Population Analyses and Reactivities for the Carboranes, R. Hoffmann and W. N. Lipscomb, J. Chem. Phys., 36, 3489 (1962). 6. The Boron Hydrides; LCAO-MO and Resonance Studies, R. Hoffmann and W. N. Lipscomb, J.Chem. Phys., 37, 2872 (1962). 7. The Excited States of Helical Polymers (in Russian), R. Hoffmann, Vestn. Moskov. Univ. Ser. Fiz. Astr., 69, (1962). -2 -2 8. Sequential Substitution Reactions on B10H10 and B12H12 , R. Hoffmann and W. N. Lipscomb, J.
    [Show full text]