25.17 Carbohydrate Structure Determination Carbohydrate Structure Determination

Total Page:16

File Type:pdf, Size:1020Kb

25.17 Carbohydrate Structure Determination Carbohydrate Structure Determination 25.17 Carbohydrate Structure Determination Carbohydrate Structure Determination Spectroscopy X-Ray Crystallography Chemical Tests once used extensively; now superceded by spectroscopic methods and x-ray crystallography reactions of carbohydrates can involve either open-chain form, furanose, or pyranose form 25.18 Reduction of Carbohydrates Reduction of Carbohydrates Carbonyl group of open-chain form is reduced to an alcohol. Product is called an alditol. Alditol lacks a carbonyl group so cannot cyclize to a hemiacetal. Reduction of D-Galactose reducing agent: NaBH4, H2O (catalytic hydrogenation can also be used) CH O CH2OH a-D-galactofuranose H OH H OH b-D-galactofuranose HO H HO H a-D-galactopyranose HO H HO H b-D-galactopyranose H OH H OH CH2OH CH2OH D-Galactitol (90%) 25.19 Oxidation of Carbohydrates Benedict's Reagent O O + 2+ – – + RCH + 2Cu + 5HO RCO + Cu2O + 3H2O Benedict's reagent is a solution of the citrate complex of CuSO4 in water. It is used as a test for "reducing sugars." Cu2+ is a weak oxidizing agent. A reducing sugar is one which has an aldehyde function, or is in equilibrium with one that does. A positive test is the formation of a red precipitate of Cu2O. Examples of Reducing Sugars Aldoses: because they have an aldehyde function in their open-chain form. Ketoses: because enolization establishes an equilibrium with an aldose. CH2OH CHOH CH O C O C OH CHOH R R R oxidized by Cu2+ Examples of Reducing Sugars Disaccharides that have a free hemiacetal function. HOCH2 HOCH2 O O Maltose HO O OH HO OH HO OH Examples of Reducing Sugars Disaccharides that have a free hemiacetal function. HOCH2 HOCH2 O OH Maltose HO O CH O HO OH HO OH oxidized by Cu2+ Glycosides are not reducing sugars HOCH2 HO O HO OH OCH3 Methyl a-D-glucopyranoside lacks a free hemiacetal function; cannot be in equilibrium with a species having an aldehyde function Oxidation of Reducing Sugars The compounds formed on oxidation of reducing sugars are called aldonic acids. Aldonic acids exist as lactones when 5- or 6- membered rings can form. A standard method for preparing aldonic acids uses Br2 as the oxidizing agent. Oxidation of D-Xylose CH O CO2H H OH H OH Br HO H 2 HO H H O H OH 2 H OH CH2OH CH2OH D-Xylose D-Xylonic acid (90%) Oxidation of D-Xylose O HO CO H HO 2 OH O H OH + HO H H OH HOCH 2 O OH O CH2OH D-Xylonic acid (90%) OH Nitric Acid Oxidation Nitric acid oxidizes both the aldehyde function and the terminal CH2OH of an aldose to CO2H. The products of such oxidations are called aldaric acids. Nitric Acid Oxidation CH O CO2H H OH H OH HNO HO H 3 HO H H OH 60°C H OH H OH H OH CH2OH CO2H D-Glucose D-Glucaric acid (41%) Uronic Acids Uronic acids contain both an aldehyde and a terminal CO2H function. CH O OH H HO2C O HO H HO H OH HO OH H OH OH CO2H D-Glucuronic acid 25.20 Cyanohydrin Formation and Carbohydrate Chain Extension Extending the Carbohydrate Chain Carbohydrate chains can be extended by using cyanohydrin formation as the key step in C—C bond-making. The classical version of this method is called the Kiliani-Fischer synthesis. The following example is a more modern modification. Extending the Carbohydrate Chain CN CH O a-L-arabinofuranose CHOH b-L-arabinofuranose H OH HCN H OH a-L-arabinopyranose HO H HO H b-L-arabinopyranose HO H HO H CH2OH CH2OH the resulting cyanohydrin is a mixture of two stereoisomers that differ in configuration at C-2; these two diastereomers are separated in the next step Extending the Carbohydrate Chain CN CN CN H OH HO H CHOH separate H OH H OH H OH H + H HO H HO H HO H HO H HO H HO H CH2OH CH2OH CH2OH L-Mannononitrile L-Gluconononitrile Extending the Carbohydrate Chain CN CH O H OH H OH H OH H2, H2O H OH HO H HO H Pd, BaSO4 HO H HO H CH2OH CH2OH L-Mannononitrile L-Mannose (56% from L-arabinose) Likewise... CN CH O HO H HO H H OH H2, H2O H OH HO H HO H Pd, BaSO4 HO H HO H CH2OH CH2OH L-Gluconononitrile L-Glucose (26% from L-arabinose) 25.21 Epimerization, Isomerization, and Retro-Aldol Reactions of Carbohydrates Enol Forms of Carbohydrates Enolization of an aldose scrambles the stereochemistry at C-2. This process is called epimerization. Diastereomers that differ in stereochemistry at only one of their stereogenic centers are called epimers. D-Glucose and D-mannose, for example, are epimers. Epimerization CH O CHOH CH O H OH C OH HO H HO H HO H HO H H OH H OH H OH H OH H OH H OH CH2OH CH2OH CH2OH D-Glucose Enediol D-Mannose This equilibration can be catalyzed by hydroxide ion. Enol Forms of Carbohydrates The enediol intermediate on the preceding slide can undergo a second reaction. It can lead to the conversion of D-glucose or D-mannose (aldoses) to D-fructose (ketose). Isomerization CH O CHOH CH2OH CHOH C OH C O HO H HO H HO H H OH H OH H OH H OH H OH H OH CH2OH CH2OH CH2OH D-Glucose or Enediol D-Fructose D-Mannose Retro-Aldol Cleavage The D-fructose 6-phosphate formed according to the preceding slide undergoes phosphorylation of its free CH2OH group to give D-fructose 1,6-diphosphate. D-Fructose 1,6-diphosphate is cleaved to two 3- carbon products by a reverse aldol reaction. This retro-aldol cleavage is catalyzed by the enzyme aldolase. Isomerization CH2OP(O)(OH)2 CH2OP(O)(OH)2 C O C O aldolase HO H CH2OH H OH H OH CH O H OH CH2OP(O)(OH)2 D-Fructose CH2OP(O)(OH)2 1,6-phosphate 25.22 Acylation and Alkylation of Hydroxyl Groups in Carbohydrates Reactivity of Hydroxyl Groups in Carbohydrates Hydroxyl groups in carbohydrates undergo reactions typical of alcohols. acylation alkylation Example: Acylation of a-D-glucopyranose O O HOCH2 HO O + 5 CH3COCCH3 HO OH OH Example: Acylation of a-D-glucopyranose O O HOCH2 HO O + 5 CH3COCCH3 HO OH OH pyridine O O CH 3COCH2 O CH3CO CH CO 3 (88%) CH CO O 3 OCCH3 O O Example: Alkylation of methyl a-D-glucopyranoside HOCH2 HO O + 4CH3I HO OH OCH3 Ag2O, CH3OH Example: Alkylation of methyl a-D-glucopyranoside HOCH2 HO O + 4CH3I HO OH OCH3 Ag2O, CH3OH CH3OCH2 O CH3O (97%) CH3O CH3O OCH3 Classical Method for Ring Size Ring sizes (furanose or pyranose) have been determined using alkylation as a key step. CH OCH HOCH2 3 2 O O HO O CH3O HO CH3O OH CH3O OCH OCH3 3 Classical Method for Ring Size Ring sizes (furanose or pyranose) have been determined using alkylation as a key step. CH3OCH2 CH3OCH2 O O CH3O H2O CH3O CH3O CH3O H+ CH3O CH3O OH OCH3 (mixture of a + b) Classical Method for Ring Size Ring sizes (furanose or pyranose) have been determined using alkylation as a key step. CH O H OCH3 CH3OCH2 O CH3O H CH3O CH3O H OCH3 CH3O H OH OH (mixture of a + b) CH2OCH3 Classical Method for Ring Size Ring sizes (furanose or pyranose) have been determined using alkylation as a key step. CH O H OCH3 This carbon has OH CH3O H instead of OCH . 3 H OCH Therefore,its O was the 3 oxygen in the ring. H OH CH2OCH3 25.23 Periodic Acid Oxidation of Carbohydrates Recall Periodic Acid Oxidation Section 15.12: Vicinal diols are cleaved by HIO4. HIO4 C C C O + O C HO OH Cleavage of a vicinal diol consumes 1 mol of HIO4. Also Cleaved by HIO4 a-Hydroxy carbonyl compounds O R HIO4 RC C C O + O C OH HO Cleavage of an a-hydroxy carbonyl compound consumes 1 mol of HIO4. One of the products is a carboxylic acid. Also Cleaved by HIO4 Compounds that contain three contiguous carbons bearing OH groups O R C CH R2C CH CR'2 HIO4 R2C O + HCOH HO OH OH + R'2C O 2 mol of HIO4 are consumed. 1 mole of formic acid is produced. Structure Determination Using HIO4 Distinguish between furanose and pyranose forms of methyl arabinoside OH HOCH 2 OH O O HO OCH3 HO HO OCH3 2 vicinal OH groups; 3 vicinal OH groups; consumes 1 mol of HIO4 consumes 2 mol of HIO4.
Recommended publications
  • Pentose PO4 Pathway, Fructose, Galactose Metabolism.Pptx
    Pentose PO4 pathway, Fructose, galactose metabolism The Entner Doudoroff pathway begins with hexokinase producing Glucose 6 PO4 , but produce only one ATP. This pathway prevalent in anaerobes such as Pseudomonas, they doe not have a Phosphofructokinase. The pentose phosphate pathway (also called the phosphogluconate pathway and the hexose monophosphate shunt) is a biochemical pathway parallel to glycolysis that generates NADPH and pentoses. While it does involve oxidation of glucose, its primary role is anabolic rather than catabolic. There are two distinct phases in the pathway. The first is the oxidative phase, in which NADPH is generated, and the second is the non-oxidative synthesis of 5-carbon sugars. For most organisms, the pentose phosphate pathway takes place in the cytosol. For each mole of glucose 6 PO4 metabolized to ribulose 5 PO4, 2 moles of NADPH are produced. 6-Phosphogluconate dh is not only an oxidation step but it’s also a decarboxylation reaction. The primary results of the pathway are: The generation of reducing equivalents, in the form of NADPH, used in reductive biosynthesis reactions within cells (e.g. fatty acid synthesis). Production of ribose-5-phosphate (R5P), used in the synthesis of nucleotides and nucleic acids. Production of erythrose-4-phosphate (E4P), used in the synthesis of aromatic amino acids. Transketolase and transaldolase reactions are similar in that they transfer between carbon chains, transketolases 2 carbon units or transaldolases 3 carbon units. Regulation; Glucose-6-phosphate dehydrogenase is the rate- controlling enzyme of this pathway. It is allosterically stimulated by NADP+. The ratio of NADPH:NADP+ is normally about 100:1 in liver cytosol.
    [Show full text]
  • MM# Modeling of Aldopentose Pyranose Rings Michael K
    Chemical and Biological Engineering Publications Chemical and Biological Engineering 2002 MM# Modeling of Aldopentose Pyranose Rings Michael K. Dowd United States Department of Agriculture William M. Rockey Iowa State University Alfred D. French United States Department of Agriculture See next page for additional authors Follow this and additional works at: http://lib.dr.iastate.edu/cbe_pubs Part of the Biochemical and Biomolecular Engineering Commons, and the Biological Engineering Commons The ompc lete bibliographic information for this item can be found at http://lib.dr.iastate.edu/ cbe_pubs/31. For information on how to cite this item, please visit http://lib.dr.iastate.edu/ howtocite.html. This Article is brought to you for free and open access by the Chemical and Biological Engineering at Iowa State University Digital Repository. It has been accepted for inclusion in Chemical and Biological Engineering Publications by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. MM# Modeling of Aldopentose Pyranose Rings Abstract MM3 (version 1992, ϵ=3.0) was used to study the ring conformations of d-xylopyranose, d-lyxopyranose and d-arabinopyranose. The nee rgy surfaces exhibit low-energy regions corresponding to chair and skew forms with high-energy barriers between these regions corresponding to envelope and half-chair forms. The lowest 4 energy conformer is C 1 for α- and β-xylopyranose and α- and β-lyxopyranose, and the lowest energy 1 conformer is C 4 for α- and β-arabinopyranose. Only α-lyxopyranose exhibits a secondary low-energy region 1 ( C 4) within 1 kcal/mol of its global minimum.
    [Show full text]
  • Fermentation of Glucose and Xylose to Hydrogen in the Presence of Long Chain Fatty Acids
    University of Windsor Scholarship at UWindsor Electronic Theses and Dissertations Theses, Dissertations, and Major Papers 2009 Fermentation of Glucose and Xylose to Hydrogen in the Presence of Long Chain Fatty Acids Stephen Reaume University of Windsor Follow this and additional works at: https://scholar.uwindsor.ca/etd Recommended Citation Reaume, Stephen, "Fermentation of Glucose and Xylose to Hydrogen in the Presence of Long Chain Fatty Acids" (2009). Electronic Theses and Dissertations. 92. https://scholar.uwindsor.ca/etd/92 This online database contains the full-text of PhD dissertations and Masters’ theses of University of Windsor students from 1954 forward. These documents are made available for personal study and research purposes only, in accordance with the Canadian Copyright Act and the Creative Commons license—CC BY-NC-ND (Attribution, Non-Commercial, No Derivative Works). Under this license, works must always be attributed to the copyright holder (original author), cannot be used for any commercial purposes, and may not be altered. Any other use would require the permission of the copyright holder. Students may inquire about withdrawing their dissertation and/or thesis from this database. For additional inquiries, please contact the repository administrator via email ([email protected]) or by telephone at 519-253-3000ext. 3208. Fermentation of Glucose and Xylose to Hydrogen in the Presence of Long Chain Fatty Acids by Stephen Reaume A Thesis Submitted to the Faculty of Graduate Studies through the Environmental Engineering Program in Partial Fulfillment of the Requirements for the Degree of Master of Applied Science at the University of Windsor Windsor, Ontario, Canada 2009 © 2009 Stephen Reaume AUTHORS DECLARATION OF ORIGINALITY I hereby certify that I am the sole author of this thesis and that no part of this thesis has been published or submitted for publication.
    [Show full text]
  • Acute and Chronic Effects of Dietary Lactose in Adult Rats Are Not Explained by Residual Intestinal Lactase Activity
    Nutrients 2015, 7, 5542-5555; doi:10.3390/nu7075237 OPEN ACCESS nutrients ISSN 2072-6643 www.mdpi.com/journal/nutrients Article Acute and Chronic Effects of Dietary Lactose in Adult Rats Are not Explained by Residual Intestinal Lactase Activity Bert J. M. van de Heijning *, Diane Kegler, Lidewij Schipper, Eline Voogd, Annemarie Oosting and Eline M. van der Beek Danone Nutricia Research, PO Box 80141, TC Utrecht 3508, The Netherlands; E-Mails: [email protected] (D.K.); [email protected] (L.S.); [email protected] (E.V.); [email protected] (A.O.); [email protected] (E.M.B.) * Author to whom correspondence should be addressed; E-Mail: [email protected]; Tel.: +31-30-2095-000. Received: 5 June 2015 / Accepted: 30 June 2015 / Published: 8 July 2015 Abstract: Neonatal rats have a high intestinal lactase activity, which declines around weaning. Yet, the effects of lactose-containing products are often studied in adult animals. This report is on the residual, post-weaning lactase activity and on the short- and long-term effects of lactose exposure in adult rats. Acutely, the postprandial plasma response to increasing doses of lactose was studied, and chronically, the effects of a 30% lactose diet fed from postnatal (PN) Day 15 onwards were evaluated. Intestinal lactase activity, as assessed both in vivo and in vitro, was compared between both test methods and diet groups (lactose vs. control). A 50%–75% decreased digestive capability towards lactose was observed from weaning into adulthood. Instillation of lactose in adult rats showed disproportionally low increases in plasma glucose levels and did not elicit an insulin response.
    [Show full text]
  • Xylose Fermentation to Ethanol by Schizosaccharomyces Pombe Clones with Xylose Isomerase Gene." Biotechnology Letters (8:4); Pp
    NREL!TP-421-4944 • UC Category: 246 • DE93000067 l I Xylose Fermenta to Ethanol: A R ew '.) i I, -- , ) )I' J. D. McMillan I ' J.( .!i �/ .6' ....� .T u�.•ls:l ., �-- • National Renewable Energy Laboratory II 'J 1617 Cole Boulevard Golden, Colorado 80401-3393 A Division of Midwest Research Institute Operated for the U.S. Department of Energy under Contract No. DE-AC02-83CH10093 Prepared under task no. BF223732 January 1993 NOTICE This report was prepared as an account of work sponsored by an agency of the United States government. Neither the United States government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, com­ pleteness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily con­ stitute or imply its endorsement, recommendation, or favoring by the United States government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States government or any agency thereof. Printed in the United States of America Available from: National Technical Information Service U.S. Department of Commerce 5285 Port Royal Road Springfield, VA22161 Price: Microfiche A01 Printed Copy A03 Codes are used for pricing all publications. The code is determined by the number of pages in the publication. Information pertaining to the pricing codes can be found in the current issue of the following publications which are generally available in most libraries: Energy Research Abstracts (ERA); Govern­ ment Reports Announcements and Index ( GRA and I); Scientific and Technical Abstract Reports(STAR); and publication NTIS-PR-360 available from NTIS at the above address.
    [Show full text]
  • Enhanced Trehalose Production Improves Growth of Escherichia Coli Under Osmotic Stress† J
    APPLIED AND ENVIRONMENTAL MICROBIOLOGY, July 2005, p. 3761–3769 Vol. 71, No. 7 0099-2240/05/$08.00ϩ0 doi:10.1128/AEM.71.7.3761–3769.2005 Copyright © 2005, American Society for Microbiology. All Rights Reserved. Enhanced Trehalose Production Improves Growth of Escherichia coli under Osmotic Stress† J. E. Purvis, L. P. Yomano, and L. O. Ingram* Department of Microbiology and Cell Science, Box 110700, University of Florida, Gainesville, Florida 32611 Downloaded from Received 7 July 2004/Accepted 9 January 2005 The biosynthesis of trehalose has been previously shown to serve as an important osmoprotectant and stress protectant in Escherichia coli. Our results indicate that overproduction of trehalose (integrated lacI-Ptac-otsBA) above the level produced by the native regulatory system can be used to increase the growth of E. coli in M9-2% glucose medium at 37°C to 41°C and to increase growth at 37°C in the presence of a variety of osmotic-stress agents (hexose sugars, inorganic salts, and pyruvate). Smaller improvements were noted with xylose and some fermentation products (ethanol and pyruvate). Based on these results, overproduction of trehalose may be a useful trait to include in biocatalysts engineered for commodity chemicals. http://aem.asm.org/ Bacteria have a remarkable capacity for adaptation to envi- and lignocellulose (6, 7, 10, 28, 30, 31, 32, 45). Biobased pro- ronmental stress (39). A part of this defense system involves duction of these renewable chemicals would be facilitated by the intracellular accumulation of protective compounds that improved growth under thermal stress and by increased toler- shield macromolecules and membranes from damage (9, 24).
    [Show full text]
  • Carbohydrates: Structure and Function
    CARBOHYDRATES: STRUCTURE AND FUNCTION Color index: . Very important . Extra Information. “ STOP SAYING I WISH, START SAYING I WILL” 435 Biochemistry Team *هذا العمل ﻻ يغني عن المصدر المذاكرة الرئيسي • The structure of carbohydrates of physiological significance. • The main role of carbohydrates in providing and storing of energy. • The structure and function of glycosaminoglycans. OBJECTIVES: 435 Biochemistry Team extra information that might help you 1-synovial fluid: - It is a viscous, non-Newtonian fluid found in the cavities of synovial joints. - the principal role of synovial fluid is to reduce friction between the articular cartilage of synovial joints during movement O 2- aldehyde = terminal carbonyl group (RCHO) R H 3- ketone = carbonyl group within (inside) the compound (RCOR’) 435 Biochemistry Team the most abundant organic molecules in nature (CH2O)n Carbohydrates Formula *hydrate of carbon* Function 1-provides important part of energy Diseases caused by disorders of in diet . 2-Acts as the storage form of energy carbohydrate metabolism in the body 3-structural component of cell membrane. 1-Diabetesmellitus. 2-Galactosemia. 3-Glycogen storage disease. 4-Lactoseintolerance. 435 Biochemistry Team Classification of carbohydrates monosaccharides disaccharides oligosaccharides polysaccharides simple sugar Two monosaccharides 3-10 sugar units units more than 10 sugar units Joining of 2 monosaccharides No. of carbon atoms Type of carbonyl by O-glycosidic bond: they contain group they contain - Maltose (α-1, 4)= glucose + glucose -Sucrose (α-1,2)= glucose + fructose - Lactose (β-1,4)= glucose+ galactose Homopolysaccharides Heteropolysaccharides Ketone or aldehyde Homo= same type of sugars Hetero= different types Ketose aldose of sugars branched unBranched -Example: - Contains: - Contains: Examples: aldehyde group glycosaminoglycans ketone group.
    [Show full text]
  • Structural Features
    1 Structural features As defined by the International Union of Pure and Applied Chemistry gly- cans are structures of multiple monosaccharides linked through glycosidic bonds. The terms sugar and saccharide are synonyms, depending on your preference for Arabic (“sukkar”) or Greek (“sakkēaron”). Saccharide is the root for monosaccha- rides (a single carbohydrate unit), oligosaccharides (3 to 20 units) and polysac- charides (large polymers of more than 20 units). Carbohydrates follow the basic formula (CH2O)N>2. Glycolaldehyde (CH2O)2 would be the simplest member of the family if molecules of two C-atoms were not excluded from the biochemical repertoire. Glycolaldehyde has been found in space in cosmic dust surrounding star-forming regions of the Milky Way galaxy. Glycolaldehyde is a precursor of several organic molecules. For example, reaction of glycolaldehyde with propenal, another interstellar molecule, yields ribose, a carbohydrate that is also the backbone of nucleic acids. Figure 1 – The Rho Ophiuchi star-forming region is shown in infrared light as captured by NASA’s Wide-field Infrared Explorer. Glycolaldehyde was identified in the gas surrounding the star-forming region IRAS 16293-2422, which is is the red object in the centre of the marked square. This star-forming region is 26’000 light-years away from Earth. Glycolaldehyde can react with propenal to form ribose. Image source: www.eso.org/public/images/eso1234a/ Beginning the count at three carbon atoms, glyceraldehyde and dihydroxy- acetone share the common chemical formula (CH2O)3 and represent the smallest carbohydrates. As their names imply, glyceraldehyde has an aldehyde group (at C1) and dihydoxyacetone a carbonyl group (at C2).
    [Show full text]
  • Fall 2014 HO OH O OH O OH
    Fall 2014! HO OH O OH O OH HO OH HO OH !-D-ribofuranose (Haworth) HO HO O O HO OH OH HO HO OH !-D-mannopyranose HO OH (Haworth) anomeric anomeric carbon carbon The anomeric monosaccharides, α-D-glucopyranose and β-D-glucopyranose, drawn as Fischer and Haworth projections, and as ball-and-stick models Upon cyclization, the carbonyl carbon becomes chiral and is referred to as the anomeric carbon. In the α-form, the anomeric OH (O1) is on the opposite side of the ring from the CH2OH group, and in the β-form, O1 is on the same side. The α- and β-forms are referred to as anomers or anomeric pairs, and they interconvert in aqueous solution via the acyclic (“linear”) form (anomerization). Aqueous solutions of D-glucose contain ~64% β-pyranose and ~36% α-pyranose. OH OH O HO HO H O HO OH OH CHO OH OH !-D-glucopyranose OH OH 37.6 % !-D-glucofuranose HO 0.11 % OH OH OH OH OH O HO H HO D-glucose O OH HO OH acyclic aldehyde OH 0.006 % OH "-D-glucopyranose OH 62.0 % "-D-glucofuranose -H2O +H2O 0.28 % CH(OH)2 OH HO OH OH OH D-glucose acyclic hydrate 0.004 % Monosaccharides that are capable of assuming a form in solution that contains a free carbonyl group can be oxidized by relatively mild oxidizing agents such as Fe+3 or Cu+2 (Fehling’s reaction). The saccharide is oxidized and the reagent is reduced.! CHO COO- OH OH HO cyclic and hydrate HO forms of D-glucose OH OH 2Cu+2 2Cu+ OH OH OH OH D-glucose D-gluconate acyclic aldehyde q " Phosphorylation can restrict the types of cyclization reactions of the acyclic carbonyl form.
    [Show full text]
  • Furanosic Forms of Sugars: Conformational Equilibrium of Methyl B-D-Ribofuranoside† Cite This: Chem
    ChemComm View Article Online COMMUNICATION View Journal | View Issue Furanosic forms of sugars: conformational equilibrium of methyl b-D-ribofuranoside† Cite this: Chem. Commun., 2016, 52,6241 Patricia E´cija,a Iciar Uriarte,a Lorenzo Spada,ab Benjamin G. Davis,c Received 5th February 2016, Walther Caminati,b Francisco J. Basterretxea,a Alberto Lesarri*d and Accepted 1st April 2016 Emilio J. Cocinero*a DOI: 10.1039/c6cc01180b www.rsc.org/chemcomm The investigation of an isolated ribofuranose unit in the gas phase reveals the intrinsic conformational landscape of the biologically active sugar form. We report the rotational spectra of two conformers of methyl b-D-ribofuranoside in a supersonic jet expansion. Both 3 conformers adopt a near twisted ( T2) ring conformation with the methoxy and hydroxymethyl substituents involved in various intra- molecular hydrogen bonds. Scheme 1 The pyranose (1) and furanose (2) constitutional isomers of ribose, together with methyl-b-D-ribofuranoside (3), in Haworth projection. Sugars are flexible polymorphic species, exhibiting complex con- stitutional, configurational and conformational isomerism. The intramolecular reaction between carbonyl (typically reducing (RNA), as substrates (ATP or sugar-diphospho-nucleosides), or as terminus) and hydroxyl groups gives rise to cyclic hemiacetal/ cofactors (NAD(P) or NAD(P)H).7 Remarkably, their roles are often ketals, particularly stable for five- or six-membered ring forms critical: DNA analogues in which thefuranoseringsareexchanged (furanose or pyranose, respectively, Scheme 1). Large amplitude by pyranoses produce double helices with much stronger base motions, like ring puckering, inversion or pseudorotation, com- pairing, but are unsuitable to replace DNA.8 The biochemical bine with the internal rotation of the hydroxyl groups to produce a functionality in ribose-based biomolecules probably relies on Published on 01 April 2016.
    [Show full text]
  • Part 1 in Our Series of Carbohydrate Lectures. in This Section, You Will Learn About Monosaccharide Structure
    Welcome to Part 1 in our series of Carbohydrate lectures. In this section, you will learn about monosaccharide structure. The building blocks of larger carbohydrate polymers. 1 First, let’s review why learning about carbohydrates is important. Carbohydrates are used by biological systems as fuels and energy resources. Carbohydrates typically provide quick energy and are one of the primary energy storage forms in animals. Carbohydrates also provide the precursors to other major macromolecules within the body, including the deoxyribose and ribose required for nucleic acid biosynthesis. Carbohydrates can also provide structural support and cushioning/shock absorption, as well as cell‐cell communication, identification, and signaling. 2 Carbohydrates, as their name implies, are water hydrates of carbon, and they all have the same basic core formula (CH2O)n and are always found in the ratio of 1 carbon to 2 hydrogens to 1 oxygen (1:2:1) making them easy to identify from their molecular formula. 3 Carbohydrates can be divided into subcategories based on their complexity. The simplest carbohydrates are the monosaccharides which are the simple sugars required for the biosynthesis of all the other carbohydrate types. Disaccharides consist of two monosaccharides that have been joined together by a covalent bond called the glycosidic bond. Oligosaccharides are polymers that consist of a few monosaccharides covalently linked together, and Polysaccharides are large polymers that contain hundreds to thousands of monosaccharide units all joined together by glycosidic bonds. The remainder of this lecture will focus on monosaccharides 4 Monosaccharides all have alcohol functional groups associated with them. In addition they also have one additional functional group, either an aldehyde or a ketone.
    [Show full text]
  • Chem 352 - Lecture 5 Carbohydrates
    Chem 352 - Lecture 5 Carbohydrates Question for the Day: Unlike amino acids, which owe their diversity to a diverse array of functional groups, monosaccharides feature primarily two functional groups, hydroxyl groups and either a ketone or aldehyde group. What, then, do monosaccharides owe their diversity to? Introduction to Carbohydrates Carbohydrates are included as one of the major classes of biological molecules: ✦ Proteins ✦ Nucleic acids ✦ Carbohydrates ✦ Lipids Chem 352, Lecture 5 - Carbohydrates 2 Introduction to Carbohydrates ✦ Carbohydrates provide a major source of energy for living organisms. ✦ They also play major structural, protective and communication roles. Chem 352, Lecture 5 - Carbohydrates 3 Introduction to Carbohydrates ✦ Carbohydrates provide a major source of energy for living organisms. ✦ They also play major structural, protective and communication roles. Chem 352, Lecture 5 - Carbohydrates 3 Introduction to Carbohydrates ✦ Carbohydrates provide a major source of energy for living organisms. ✦ They also play major structural, protective and communication roles. Chem 352, Lecture 5 - Carbohydrates 3 Introduction to Carbohydrates Carbohydrates are chemically simple, but structurally complex ✦ (CH2O)n Like amino acid, simple sugars (monosaccharides) can combine to form polymers. ✦ monosaccharides (monomer) ✦ oligosaccharides (several monomers linked together) ✦ polysaccharides (many monomers linked together Chem 352, Lecture 5 - Carbohydrates 4 Monosaccharides Monosaccharides are ✦ either Aldoses ‣ polyhydroxylaldehydes
    [Show full text]