- Synthesis and Conformational Analysis of (6R)--1,2:3,4-Di-O-isopropylidene-α-D-galactopyranose. NMR and Molecular Modeling Studies
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The conformation preferences of 1,2:3,4-di-O-isopropylidene-α-D-galactopyranose have been determined using NMR and molecular modeling (conformational searching) techniques.The pyranose ring assumes a skew-boat conformation.Coupling constants for the C6 side chain and hydroxyl proton indicate that the predominant conformation places the oxygen anti to C4 (gt conformation) with the hydroxyl hydrogen aligned toward the pyranose oxygen in deuteriochloroform.A similar orientation of the C5-C6 bond was observed in water and toluene.In DMSO the C6 oxygen is anti to the pyranose oxygen (tg conformation) with the hydroxyl hydrogen anti to C5.A similar orientation of the C5-C6 bond was observed in methanol.
- Midland, M. Mark,Asirwatham, Gitanjali,Cheng, John C.,Miller, Jennifer A.,Morell, Luis A.
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- Synthesis and Biological Evaluation of 6-[(1 R)-1-Hydroxyethyl]-2,4a(R),6(S),8a(R)-tetrahydropyrano-[3,2- b]-pyran-2-one and Structural Analogues of the Putative Structure of Diplopyrone
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The phytotoxin diplopyrone is considered to be the main phytotoxin in a fungus that is responsible for cork oak decline. A carbohydrate-based synthesis of the enantiomer of the structure proposed for diplopyrone has been developed from a commercially available derivative of d-galactose. Key steps in the synthesis are a highly stereoselective pyranose chain-extension based on methyltitanium, preparation of a vinyl glycoside via Isobe C-alkynylation-rearrangement/reduction, and RCM-based pyranopyran construction. Crystallographic and NMR analysis confirms an earlier report that the structure originally proposed for diplopyrone may require revision. Structural analogues were prepared for biological evaluation, the most promising being a pyranopyran nitrile synthesized from tri-O-acetyl-d-galactal by Ferrier cyanoglycosidation, Wittig chain extension, and lactonization. Biological assays revealed potent antibacterial activity for the nitrile analogue against common bacterial pathogens Edwardsiella ictaluri and Flavobacterium columnare that cause enteric septicemia (ESC) and columnaris disease, respectively, in catfish. The IC50 value of 0.002 against E. ictaluri indicates approximately 100 times greater potency than the antibiotic florfenicol used commercially for this disease. Phytotoxic activity for all three target compounds against duckweed was also observed. The antibiotic and phytotoxic activities of the new pyranopyrans synthesized in this study demonstrate the potential of such compounds as antibiotics and herbicides.
- Lazzara, Nicholas C.,Rosano, Robert J.,Vagadia, Purav P.,Giovine, Matthew T.,Bezpalko, Mark W.,Piro, Nicholas A.,Kassel, Wm. Scott,Boyko, Walter J.,Zubris, Deanna L.,Schrader, Kevin K.,Wedge, David E.,Duke, Stephen O.,Giuliano, Robert M.
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- Synthesis and conformational properties of methyl 6,6-di-C-methyl-beta-D-galactopyranoside. Probes for the combining sites of D-galactosyl-binding proteins.
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The binding of D-galactopyranosyl groups by lectins and antibodies can involve the 5-hydroxymethyl group. In order to examine the nature of these binding reactions, it was of interest to synthesize 6,6-di-C-methyl-D-galactose which was found to exist, like D-galactose, extensively in the pyranose forms. 2,3,4,6-Tetra-O-acetyl-7-deoxy-6-C-methyl-alpha-D-galacto-heptopyranosyl bromide was prepared under standard conditions and converted into methyl 6,6-di-C methyl-beta-D-galactopyranoside (6). Evidence based on 13C-n.m.r. studies indicates that the favored conformer of 6 has O-4 and O-6 in syn-axial-like relationship. General comments are presented on the nature of the binding of oligosaccharides by proteins.
- Lough,Hindsgaul,Lemieux
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- The synthesis and conformational properties of the diastereoisomeric βDGal(1-4)βDGlcNAc(1-6)6-C-CH3-D-Gal trisaccharides
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The trisaccharide βDGal(1->4)βDGlcNAc(1->6)DGal was known to be bound strongly by the so-called anti-I Ma monoclonal antibody.In order to help assess the conformation about the 1->6 glycosidic linkage that is accepted by the antibody combining site, the conformationally well-defined βDGal(1->4)βDGlcNAc(1->6) derivatives of 7-deoxy-L-glycero-D-galacto-heptopyranose and 7-deoxy-D-glycero-D-galacto-heptopyranose were synthesized.The conformational preferences for these trisaccharides were estabished by 1H nmr spectroscopy and rationalized by computer-assisted molecular modelling.
- Lemieux, Raymond U.,Wong, Ting C.,Thogersen, Henning
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- Biocatalytic Production of Amino Carbohydrates through Oxidoreductase and Transaminase Cascades
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Plant-derived carbohydrates are an abundant renewable resource. Transformation of carbohydrates into new products, including amine-functionalized building blocks for biomaterials applications, can lower reliance on fossil resources. Herein, biocatalytic production routes to amino carbohydrates, including oligosaccharides, are demonstrated. In each case, two-step biocatalysis was performed to functionalize d-galactose-containing carbohydrates by employing the galactose oxidase from Fusarium graminearum or a pyranose dehydrogenase from Agaricus bisporus followed by the ω-transaminase from Chromobacterium violaceum (Cvi-ω-TA). Formation of 6-amino-6-deoxy-d-galactose, 2-amino-2-deoxy-d-galactose, and 2-amino-2-deoxy-6-aldo-d-galactose was confirmed by mass spectrometry. The activity of Cvi-ω-TA was highest towards 6-aldo-d-galactose, for which the highest yield of 6-amino-6-deoxy-d-galactose (67 %) was achieved in reactions permitting simultaneous oxidation of d-galactose and transamination of the resulting 6-aldo-d-galactose.
- Aumala, Ville,Mollerup, Filip,Jurak, Edita,Blume, Fabian,Karppi, Johanna,Koistinen, Antti E.,Schuiten, Eva,Vo?, Moritz,Bornscheuer, Uwe,Deska, Jan,Master, Emma R.
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- ANALOGS OF CELL SURFACE CARBOHYDRATES. SYNTHESIS OF D-GALACTOSE DERIVATIVES HAVING AN ETHYNYL, VINYL OR EPOXY RESIDUE AT C-5
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Compounds derived from D-galactose having an ethynyl, vinyl, or epoxide residue at C-5, as well as 7,7-dibromo olefinic, isomeric 7,7-gem-bromofluoro olefinic, and 6,6-gem-difluoro derivatives were obtained from 1,2:3,4-di-O-isopropylidene-α-D-galacto-hexodialdo-1,5-pyranose.
- Lee, Ho H.,Hodgson, Philip G.,Bernacki, Ralph J.,Korytnyk, Walter,Sharma, Moheswar
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- Total Synthesis of β- D -ido-Heptopyranosides Related to Capsular Polysaccharides of Campylobacter jejuni HS:4
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The 6-deoxy-β-d-ido-heptopyranoside related to the capsular polysaccharides of C. jejuni HS:4 is very remarkable, owing to the unique, multifaceted structural features that have been combined into one molecule, which include (1) the rare ido-configuration, (2) the unusual 7-carbon backbone, and (3) the challenging β-(1→2)-cis-anomeric configuration. Two distinct strategies toward the total synthesis of this interesting target are reported. The first involved establishment of the β-d-idopyranosyl configuration from β-d-galactopyranosides, prior to a C-6-homologation extending the d-hexose to the desired 6-deoxy-d-heptose. However, this approach encountered difficulties due to the significantly reduced reactivity of the 6-position of the β-d-idopyranosides, so instead a second strategy was employed, which involved first carrying out a 6-homologation on the less flexible d-galactopyranose, followed by a very successful conversion to the desired β-d-ido-configuration found in the target heptopyranoside (2). This report is the first successful synthesis of the 6-deoxy-β-d-ido-heptopyranoside, which could possess interesting immunological properties.
- Zhang, Pengfei,Hevey, Rachel,Ling, Chang-Chun
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- Synthesis, characterization and cytotoxicity of cyclopentadienyl ruthenium(II) complexes containing carbohydrate-derived ligands Dedicated to Prof. Maria José Calhorda on the occasion of her 65th birthday.
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We here report the synthesis of new cyclopentadienyl ruthenium(II) complexes of general formula [(η5-C5H 5)Ru(PP)(L)]+ (PP = two triphenylphosphine, 1,2-diphenylphosphinoethane), isolated as PF6- salts, with L b
- Florindo, Pedro,Marques, Inês J.,Nunes, Carla D.,Fernandes, Ana C.
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- Multicomponent Approach to Homo-and Hetero-Multivalent Glycomimetics Bearing Rare Monosaccharides
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We applied a multicomponent approach to access a library of densely functionalized homo-and hetero-multivalent glycomimetics comprising aldehyde, amine, and isocyanide components related to isopropylidene-protected d-fructose, l-sorbose, d-galactose, and d-Allose. Passerini products were obtained in very good yields (up to 78%) and high diastereoselectivities (up to 98:2). Three types of products were obtained by the Ugi reaction; along with the "classical" four-component product, α-Acylaminoamides, a three-component α-Aminoamides, and a four-component α-Aminoacylamides were isolated. The presence of multiple pathways is rationalized by the structure of the imidate intermediate, mainly influenced by the amine component.
- Jakas, Andreja,Jeri?, Ivanka,Vi?njevac, Aleksandar
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p. 3766 - 3787
(2020/03/30)
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- Methods Of Making Pyranopyrans Such As Pyranopyran Nitrile And Methods of Using Pyranopyrans Such As Pyranopyran Nitrile
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Disclosed herein are methods of making (4aR,6S,8aR)-6-((R)-1-hydroxyethyl)-6,8a-dihydropyrano[3,2-b]pyran-2-(4aH)-one (2) and methods of making (4aR,6S,8aR)-6-cyano-6,8a-dihydropyrano-[3,2-b]pyran-2(4aH)-one (4). Other pyranopyrans were also synthesized. Also compositions containing (4aR,6S,8aR)-6-cyano-6,8a-dihydropyrano-[3,2-b]pyran-2(4aH)-one (4) (or other pyranopyrans described herein) and optionally a carrier. In addition, methods for killing microorganisms or weeds on or in an object or area involving contacting the object or area with an effective microorganisms or weeds killing amount of a composition containing (4aR,6S,8aR)-6-cyano-6,8a-dihydropyrano-[3,2-b]pyran-2(4aH)-one (4) (or other pyranopyrans described herein) and optionally a carrier.
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Paragraph 0018; 0040; 0071
(2020/04/10)
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- N-Alkylated C-Glycosyl Amino Acid Derivatives: Synthesis by a One-Pot Four-Component Ugi Reaction
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C-glycosides represent an important group of naturally occurring glycosylation derivatives but are also efficient mimetics of native O-glycosides. Here, a one-pot four-component methodology is described toward a library of N-alkylated C-glycosyl amino acid derivatives comprising seven different isopropylidene-protected carbohydrate units. The applied methodology tolerates different amines and isocyanides and provides access to Ugi products in yields up to 85 %. X-ray analysis of selected products bearing three different carbohydrate motifs and comparison of their crystal structures with similar ones deposited in Cambridge Crystallographic Database revealed that four structures adopt different conformations, mostly not typical for peptide structures. This property opens the possibility to exploit here described N-alkylated C-glycosyl amino acid derivatives as templates to access different biotic and abiotic secondary structures.
- ?tefani?, Zoran,Jeri?, Ivanka,Vazdar, Katarina,Vlahovi?ek-Kahlina, Kristina
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p. 838 - 844
(2020/06/02)
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- Synthesis of reversed C-glycopeptide mimics monomer from galactose via passerini reaction
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C-glycopeptidomimetics are formed by the condensation of sugar unit and analogues of amino acid residue which generates a new carbon-carbon sigma bond. In glycopeptides, this condensation occurs in side chain of amino acid but introduction of isonitrile moiety on N-terminal of amino acid mimic unit can also be a route to produce such compounds. It is observed that C-glycopeptidomimetics are more stable than their N- and O-analogues under physiological conditions but their synthesis is a challenging task due to relatively less reactive C-6 position of hexose. In present work, synthesis of reversed C-glycopeptidomimetics (pseudoglycopeptides) was done by Passerini reaction protocol which is famous for peptide synthesis due to its mild conditions and easy workup. This paper discusses the use of α-D-galactose, a cheap and easily available monosaccharide to prepare reversed C-glycopeptidomimetics. The term reversed C-glycopeptidomimetics is derived for its analogy with reversed C-nucleosides, as in these reactions, instead of anomeric carbon i.e. more reactive site, C-6 undergoes to produce desired products.
- Jalib, Muhammad Atif,Nabeel, Muhammad,Ali, Firdous Imran,Bari, Ahmed,Musharraf, Syed Ghulam,Hashmi, Imran Ali
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p. 792 - 798
(2018/07/15)
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- Synthesis of 5-C-Methylated d -Mannose, d -Galactose, l -Gulose, and l -Altrose and Their Structural Elucidation by NMR Spectroscopy
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C5/C6-Spirocyclopropanation of exocyclic enol esters followed by alkali ring-opening of the three-membered ring was used for the diastereoselective preparation of 5-C-methylated d-mannose, d-galactose, l-gulose, and l-altrose. Extensive NMR studies demons
- K?llmann, Christoph,Jones, Peter G.,Werz, Daniel B.
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supporting information
p. 1220 - 1223
(2018/02/22)
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- Practical Aerobic Oxidation of Alcohols: A Ligand-Enhanced 2,2,6,6-Tetramethylpiperidine-1-oxy/Manganese Nitrate Catalyst System
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A highly efficient, ligand-enhanced 2,2,6,6-tetramethylpiperidine-1-oxy (TEMPO)/Mn(NO3)2 catalyst system for the aerobic oxidation of alcohols is described. From the series of coordinating ligands studied herein, 2-picolinic acid (PyCOOH) improves the catalytic activity of TEMPO/Mn(NO3)2 remarkably. Under ambient air at room temperature in acetic acid, the ligand-enhanced catalyst converts aliphatic and benzylic primary alcohols that bear various functional groups into their respective aldehydes with near quantitative conversions. The applicability of the catalyst for convenient preparative synthesis was demonstrated by conducting oxidations on a gram scale. A change of TEMPO to the sterically less demanding 9-azabicyclo[3.3.1]nonane N-oxyl results in a Mn catalyst that is also able to oxidize secondary alcohols to ketones. Mechanistic studies showed that alcohols are oxidized by the oxoammonium cation derived from the nitroxyl radical. The active oxidant is regenerated by Mn(NO3)2, and this process is greatly promoted by the coordination of PyCOOH to Mn.
- Lagerblom, Kalle,Lagerspets, Emi,Keskiv?li, Juha,Cook, Chris,Ekholm, Filip,Parviainen, Arno,Repo, Timo
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p. 3880 - 3887
(2017/09/28)
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- Covalent Lectin Inhibition and Application in Bacterial Biofilm Imaging
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Biofilm formation by pathogenic bacteria is a hallmark of chronic infections. In many cases, lectins play key roles in establishing biofilms. The pathogen Pseudomonas aeruginosa often exhibiting various drug resistances employs its lectins LecA and LecB as virulence factors and biofilm building blocks. Therefore, inhibition of the function of these proteins is thought to have potential in developing “pathoblockers” preventing biofilm formation and virulence. A covalent lectin inhibitor specific to a carbohydrate binding site is described for the first time. Its application in the LecA-specific in vitro imaging of biofilms formed by P. aeruginosa is also reported.
- Wagner, Stefanie,Hauck, Dirk,Hoffmann, Michael,Sommer, Roman,Joachim, Ines,Müller, Rolf,Imberty, Anne,Varrot, Annabelle,Titz, Alexander
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p. 16559 - 16564
(2017/12/04)
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- Highly enantioselective intermolecular hydroamination of allylic amines with chiral aldehydes as tethering catalysts
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Chirally LinkedIn: Chiral aldehydes are effective tethering catalysts for enantioselective intermolecular hydroamination, which provides access to vicinal diamine motifs in good yields and excellent enantioselectivities (see scheme). This work highlights simple chiral α-oxygenated aldehydes as effective organocatalysts capable of efficiently inducing asymmetry through transient intramolecularity. Copyright
- MacDonald, Melissa J.,Hesp, Colin R.,Schipper, Derek J.,Pesant, Marc,Beauchemin, André M.
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supporting information
p. 2597 - 2601
(2013/03/14)
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- Design, synthesis and antifibrotic activities of carbohydrate-modified 1-(substituted aryl)-5-trifluoromethyl-2(1H) pyridones
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Pirfenidone, a pyridone compound, is an effective and novel antifibrotic agent. In this article, we describe the design, synthesis and activity evaluation of novel antifibrotic agents, 1-(substituted aryl)-5-trifluoromethyl- 2(1H) pyridones modified with
- Lou, Qinghua,Meng, Xiangbao,Lao, Zhiqi,Xuan, Lingling,Bai, Jinye,Hou, Qi,Hu, Gaoyun,Luo, Renna,Tao, Lijian,Li, Zhongjun
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scheme or table
p. 884 - 896
(2012/03/09)
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- Intramolecular cyclization of alkoxyaminosugars: Access to novel glycosidase inhibitor families
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We report the synthesis of two novel families of iminosugars as glycosidase inhibitors involving an intramolecular cyclization between an N-alkoxyamino group and a latent aldehyde of a reducing sugar as the key step. Using this methodology we have prepare
- Martínez-Castro, Elisa,González-Benjumea, Alejandro,López, óscar,Maya, Inés,álvarez, Eleuterio,Fernández-Bola?os, José G.
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scheme or table
p. 4220 - 4228
(2012/07/14)
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- One-Pot Bi(OTf)catalyzed oxidative deprotection of tert -butyldimethyl silyl ethers with TEMPO and co-oxidants
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A sequential one-pot synthesis for the oxidation of primary and secondary tert-butyldimethylsilyl (TBDMS) ethers, using catalytic amounts of metal triflates and TEMPO in combination with PhIO or PhI(OAc)in THF or acetonitrile, is described. Acid-sensitive protecting groups such as methylidene, isopropylidene, acetals, and Boc are unaffected under the reaction conditions. Another feature of this procedure is its high selectivity for TBDMS ethers over tert-butyldiphenylsilyl ethers and of aliphatic TBDMS groups over phenolic TBDMS groups. Georg Thieme Verlag Stuttgart - New York.
- Barnych, Bogdan,Vatèle, Jean-Michel
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experimental part
p. 2048 - 2052
(2011/10/19)
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- Diastereoselective synthesis of lincosamine precursors
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The stereoselective syntheses of the four aminodiol precursors of the diastereomers of lincosamine are reported. The procedure is based on the initial two-carbon elongationof 1,2;3,4-di-O-isopropylidene-α-D- galactohexodialdo-1,5-pyranose, followed by the stereocontrolled introduction of the amino group by nucleophilic amination. Two complementary approaches have been investigated and compared: The first one is the direct transformation of α-chloroglycidic ester into β-amino-α-keto ester. The second strategy is a three-step synthesis that is based on the treatment of the β-iodo-α-keto ester with dibenzylamine. Subsequent reduction of the β-amino-α-keto ester provides the pure D-erythro, L-threo, L-erythro, and D-threo aminodiols after chromatographic purification. Further classical transformations afford the N-acetyl derivatives, which are key precursors of the lincosamine diastereomers. Copyright
- Serra, Fiona,Coutrot, Philippe,Esteve-Quelquejeu, Melanie,Herson, Patrick,Olszewski, Tomasz K.,Grison, Claude
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p. 1841 - 1847
(2011/05/09)
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- Synthesis of fluorinated Thomsen-Friedenreich antigens: Direct deoxyfluorination of αgalNAc-threonine tert-butyl esters
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Selectively 6-fluorinated analogs of the tumor-associated TN antigen Fmoc-Thr(α-O-GalNAc)-OtBu can be efficiently prepared using DAST-mediated de(hydr)oxyfluorination reactions of preformed and orthogonally protected glycosyl amino esters witho
- Johannes, Manuel,Oberbillig, Thomas,Hoffmann-Roeder, Anja
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supporting information; experimental part
p. 5541 - 5546
(2011/08/21)
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- A one-pot oxidation/allylation/oxidation sequence for the preparation of β,γ-unsaturated ketones directly from primary alcohols
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A one-pot oxidation/allylation/oxidation procedure has been developed for the conversion of primary alcohols into β,γ-unsaturated ketones. The methodology has been applied to a range of alcohols, and in some cases, isomerisation to produce the corresponding α,β-unsaturated ketones has been carried out.
- Moody, Catherine L.,Pugh, David S.,Taylor, Richard J.K.
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experimental part
p. 2511 - 2514
(2011/05/09)
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- A green procedure for the regio- and chemoselective hydrophosphonylation of unsaturated systems using CaO under solventless conditions
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Diethyl phosphite and diphenylphosphine add to a series of unsaturated derivatives using environmentally-friendly calcium oxide as a basic promoter under solventless conditions at room temperature. The corresponding adducts are obtained in a totally regio
- Martinez-Castro, Elisa,Lopez, Oscar,Maya, Ines,Fernandez-Bolanos, Jose G.,Petrini, Marino
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scheme or table
p. 1171 - 1174
(2010/10/18)
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- Polymer-assisted dithane hydrolysis with minimum workup
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(Chemical Equation Presented) The first solid-phase-assisted protocol for the hydrolysis of dithioacetals is described using three different functionalized ion exchange resins. The hydrolysis and the purification proceed under milder conditions than common homogeneously employed reagents so that very reactive carbonyl compounds can be prepared.
- Luiken, Silke,Kirschning, Andreas
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p. 2018 - 2020
(2008/09/21)
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- A new versatile strategy for C-aryl glycosides
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(Chemical Equation Presented) A versatile strategy involving a sequential intermolecular enyne metathesis of C-alkynyl glycosides with ethylene, Diels-Alder, and aromatization reactions is successfully developed to provide a range of C-aryl glycosides.
- Kaliappan, Krishna P.,Subrahmanyam, Ayyagari V.
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p. 1121 - 1124
(2007/10/03)
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- Synthesis of octoses by brimacombe methodology; a hard proof for the structure of the anti-Kishi product of osmylation of unsaturated ester
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Reaction of 1,2:3,4-di-O-isopropylidene-α-D-galactopyranos-6-ulose with Ph3P=CH-CO2Me conducted in methanol afforded exclusively the Z-α,β-unsaturated ester, which was further reduced with DIBAL-H to the allylic alcohol. Osmylation o
- Jarosz,Osuch,Luboradzki
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p. 521 - 527
(2008/09/17)
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- Dihydroxyacetone variants in the organocatalytic construction of carbohydrates: Mimicking tagatose and fuculose aldolases
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Dihydroxyacetone variants have been explored as donors in organocatalytic aldol reactions with various aldehyde and ketone acceptors. The protected form of dihydroxyacetone that was chosen for in-depth study was 2,2-dimethyl-1,3- dioxan-5-one, 1. Among the catalysts surveyed here, proline proved to be superior in terms of yield and stereoselectivities in the construction of various carbohydrate scaffolds. In a fashion analogous to aldolase enzymes, the de novo preparation of L-ribulose, L-lyxose, D-ribose, D-tagatose, 1-amino-1-deoxy-D-lyxitol, and other carbohydrates was accomplished via the use of 1 and proline. In reactions using 2,2-dimethyl-1,3-dioxan-5-one 1 as a donor, (S)-proline can be used as a functional mimic of tagatose aldolase, whereas (R)-proline can be regarded as an organocatalytic mimic of fuculose aldolase.
- Suri, Jeff T.,Mitsumori, Susumu,Albertshofer, Klaus,Tanaka, Fujie,Barbas III, Carlos F.
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p. 3822 - 3828
(2007/10/03)
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- Practical TEMPO-mediated oxidation of alcohols using different polymer-bound co-oxidants
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Hypochlorite and chlorite exchange resins are evaluated as co-oxidants or oxidants, respectively, for the oxidation of alcohols to the corresponding aldehydes, ketones or carboxylic acids. Polymer-bound hypochlorite can act as a co-oxidant in TEMPO-mediated oxidations of alcohols. The formation of aldehydes only works under weakly acidic conditions. However, the cheap hypochlorite exchange resin is less efficient as co-oxidant compared to the use of ionically immobilised bisacetoxybromate(I) anions. In contrast, the chlorite exchange resin is a highly potent co-oxidant for the preparation of carboxylic acids from the corresponding primary alcohols in the presence of TEMPO. It is demonstrated that in this case also the resin acts as a polymer-bound co-oxidant for both oxidation steps. Yields are commonly excellent as is also demonstrated for examples taken from natural product synthesis which include acid labile glycosides. In most cases, work-up of this heavy metal-free oxidation is kept to a minimum. It often includes filtration followed by removal of the solvent.
- Kloth, Katrin,Bruenjes, Marco,Kunst, Eike,Joege, Thomas,Gallier, Florian,Adibekian, Alexander,Kirschning, Andreas
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p. 1423 - 1434
(2007/10/03)
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- Stereoselective cycloaddition on carbohydrates for the synthesis of new bicyclic oxazolidines bearing a quaternary bridgehead
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A new carbohydrate nitrone intramolecular cycloaddition reaction is described for the enantioselective synthesis of bicyclic oxazolidines. By choice of the precursor, the products possess a chiral quaternary bridgehead aryl substitution. Also described is the diverse synthesis of 6-keto and 6-alkenyl carbohydrates by a general approach. The overall protocol provides versatility through the possibility of introducing diverse reagents at several entry points. Georg Thieme Verlag Stuttgart.
- Bashiardes, George,Cano, Céline,Mauzé, Bernard
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p. 1425 - 1428
(2007/10/03)
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- Use of lithium hexafluoroisopropoxide as a mild base for Horner-Wadsworth-Emmons olefination of epimerizable aldehydes
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(Chemical Equation Presented) The weak base lithium 1,1,1,3,3,3- hexafluoroisopropoxide (LiHFI) is shown to be highly effective as a reagent for intermolecular Horner-Wadsworth-Emmons (HWE) olefination of epimerizable aldehydes with trimethyl phosphonoace
- Blasdel, Landy K.,Myers, Andrew G.
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p. 4281 - 4283
(2007/10/03)
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- Diastereoselective synthesis of galactopyranosyl amino esters and their transformation into C-nucleosides
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Galactopyranosylated olefinic ester (4) on conjugate addition of amines yielded stereoselectively galactopyranosylated amino esters (5-18) in fair to good yield. The selected amino esters (5, 6, 13, and 15-17) on reaction with isocyanates resulted in urei
- Katiyar, Diksha,Mishra, Ram Chandra,Tripathi, Rama Pati
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- Polymer-Supported Bisacetoxybromate(I) Anion - An Efficient Co-Oxidant in the TEMPO-Mediated Oxidation of Primary and Secondary Alcohols
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A polymer-bound reagent for the efficient oxidation of primary alcohols to aldehydes and secondary alcohols to ketones in the presence of a catalytic amount of 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) is described. The oxidation process is particular mild and allows one to prepare aldehydes with α-chirality without racemization. This also includes the synthesis of α-aminoaldehydes. In most cases, work-up of this heavy metal-free oxidation is achieved by simple filtration followed by removal of the solvent. Insight into the role of the bromate(I) anion in the oxidation process was gained from the TEMPO-mediated oxidation of benzaldehyde in the presence of the hypochlorite anion loaded on an anion exchange resin.
- Bruenjes, Marco,Sourkouni-Argirusi, Georgia,Kirschning, Andreas
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p. 635 - 642
(2007/10/03)
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- Synthesis of amino-substituted hexo- and heptopyranoses from D-galactose
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After condensation of D-galactose with two equivalents of acetone, the last free hydroxy group was transformed into an acylated amino group by Swern oxidation, oxime formation, LiAlH4 reduction and acylation. The intermediate aldehyde was homol
- Streicher, Benedikt,Wuensch, Bernhard
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p. 2375 - 2385
(2007/10/03)
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- A New Polymer-attached Reagent for the Oxidation of Primary and Secondary Alcohols
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formula presented A new, polymer-bound reagent system for the efficient oxidation of primary alcohols to aldehydes and secondary alcohols to ketones in the presence of a catalytic amount of 2,2,6,6-tetramethyl-1-piperidinyloxyl (TEMPO) is described. In most cases, workup of this heavy metal-free oxidation is achieved by simple filtration followed by removal of the solvent. In selected examples this reagent was compared with the known polymer-bound permanganate and chromium(VI) reagents.
- Sourkouni-Argirusi, Georgia,Kirschning, Andreas
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p. 3781 - 3784
(2007/10/03)
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- Polyhydroxy amino acid derivatives via β-lactams using enantiospecific approaches and microwave techniques
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Enantiospecific synthesis has been developed for α-hydroxy β-lactams of predictable absolute configuration starting with readily available carbohydrates. Stereospecific approaches and microwave assisted chemical reactions have been utilized for the prepar
- Bose, Ajay K.,Banik, Bimal K.,Mathur, Chandra,Wagle, Dilip R.,Manhas, Maghar S.
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p. 5603 - 5619
(2007/10/03)
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- An olefin metathesis route for the preparation of (1 → 6)-linked C-disaccharide glycals. A convergent and flexible approach to C-saccharide synthesis
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A convergent route to a variety of C-1-disaccharide glycals based on the olefin metathesis reaction of enol ethers and alkenes is described. The DCC-mediated coupling reaction of a variety of pentose enitols (1a-c) with a number of C-5- and C-6-monosaccharide carboxylic acids (2a-e) gave the corresponding esters 3a-1 in good yield. Methylenation of these compounds was followed by ring-closing metathesis, mediated by the Schrock molybdenum catalyst 8 in warm toluene, to provide the target C-disaccharide glycals 5a-1. The formed enol ether double bond in 5a was then transformed, via standard manipulations, into a variety of C-disaccharide derivatives 21-25.
- Postema, Maarten H. D.,Calimente, Daniel,Liu, Lei,Behrmann, Tonja L.
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p. 6061 - 6068
(2007/10/03)
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- New method of in situ generation of nitrile oxides by MnO2 oxidation of aldoximes
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Manganese(IV) oxide (MnO2) was found to oxidize aldoximes to nitrile oxides. Nitrile oxides were trapped in situ with dipolarophiles to furnish 2- oxazolines. The best results were obtained with hydroximinoacetates as nitrile oxide precursors.
- Kiegiel, Jaroslaw,Poplawska, Magdalena,Jozwik, Julita,Kosior, Malgorzata,Jurczak, Janusz
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p. 5605 - 5608
(2007/10/03)
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- Asymmetric nucleophilic acylation of aldehydes via 1,1-heterodisubstituted alkenes
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Aldehydes are asymmetrically acylated by a two step sequence that is initiated by a homologation step to 1,1-heterodisubstituted alkenes followed by asymmetric dihydroxylation. Thus, ketene O,S-acetals are efficiently prepared from aldehydes by a Peterson olefination with lithiated methoxy-phenylthiotrimethylsilyl methane 14 as the C-1 source. Although they are dihydroxylated with the Sharpless catalyst with moderate to good enantioselectivity (62-80% ee), the process is not efficient owing to the low chemical yields of the desired α-hydroxy methyl esters (7-37%). Use of the corresponding sulfoxide 24 or sulfon 25 led to an improved chemical yield of α-hydroxy methyl ester 19, but the stereoselectivity was diminished. In contrast, intermediate ketene O,O-acetals are prepared by a Horner-Wittig reaction with phosphine oxide 31 and are dihydroxylated both with good chemical and stereochemical yield. The concept is applicable to aromatic, aliphatic, and chiral aldehydes. For example, this short sequence allows exclusive and independent preparation of both diastereomeric heptoses 69 a and 69 b.
- Monenschein, Holger,Draeger, Gerald,Jung, Alexander,Kirschning, Andreas
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p. 2270 - 2280
(2007/10/03)
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- Chemoenzymic approaches to the preparation of 5-C- (hydroxymethyl)hexoses
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Synthesis of 5-C-(hydroxymethyl)hexoses, carbohydrates resistant to metabolism, is described. These compounds are obtained in the reaction of hexose 6-aldehydes with formaldehyde. 5-C-(Hydroxymethyl)-L-arabino- hexopyranoses can be efficiently obtained from D-galactosides by a two-step chemoenzymic synthesis using galactose oxidase for the preparation of required hexose 6-aldehydes. This method is an example of carbohydrate synthesis without use of protecting groups. Other 5-C-(hydroxymethyl)hexoses are prepared by a typical chemical methodology requiring specific protection of the hexose hydroxyl groups.
- Mazur,Hiler II
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p. 4471 - 4475
(2007/10/03)
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- Diastereoselectivity in the synthesis of D-glycero-D-aldoheptoses by 2-trimethylsilylthiazole homologation from hexodialdo-1,5-pyranose derivatives
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An exploration of the synthesis of D-glycero-D-altro-heptose, a constitutent of O antigen chains in lipopolysaccharides from Campylobacter jejuni serotypes O:23 and O:36 led to a study of the 2-trimethylsilylthiazole homologation procedure for heptose syn
- Khare,Sood,Aspinall
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p. 237 - 246
(2007/10/02)
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- CHIRAL β-LACTAMS AS SYNTHONS. STEREOSPECIFIC SYNTHESIS OF A 6-EPI-LINCOSAMINE DERIVATIVE
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A derivative of 6-epi-lincosamine has been prepared by a sequence of stereospecific steps from an optically active, cis-α-hydroxy-β-lactam.This β-lactam was obtained by an enantiospecific cycloaddition reaction between methoxyacetyl chloride, triethylamin
- Bose, Ajay K.,Mathur, Chandra,Wagle, Dilip R.,Naqvi, Raza,Manhas, Maghar S.,Urbanczyk-Lipkowska, Zofia
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p. 491 - 496
(2007/10/02)
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- Practical hydroxymethylation of aldehydes and ketones via pinacol cross-coupling reactions with paraformaldehyde
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A general and practical method for the direct hydroxymethylation of aldehydes and ketones via pinacol cross-coupling with paraformaldehyde is described. The reaction is promoted by vanadium(II) ions which are conveniently generated from the reduction of VCl3(THF)3 with zinc dust. Excellent yields of terminal diols are obtained and stereoselective coupling is observed with some chiral aldehydes and ketones.
- Park, Jeonghan,Pedersen, Steven F.
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p. 2069 - 2080
(2007/10/02)
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- Dihydropyridines chirales modeles de NADH: preparation d'esters de Hantzsch substitues par des monosaccharides
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The 1,4-dihydropyridine ring of Hantzsch esters (HEH) was chosen as NADH models to perform chemical reductions; chiral HEH were prepared for the sake of asymmetric reductions and, for that purpose, sugar substituents were introduced on the 4- or both 3- and 5- position of the HEH ring by means of a one pot cyclisation reaction using suitable monosaccharides derivatives.
- Zehani, Sadek,Llauro, Marie-France,Gelbard, Georges
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p. 104 - 113
(2007/10/02)
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- APPLICATION OF THE BUCHERER REACTION TO CARBOHYDRATE DERIVATIVES
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The Bucerer reaction of carbohydrate derivatives having a free carbonyl group proceeds normally, giving mainly the expected spiro-hydantoin derivatives.With derivatives having a free aldehydo group attached to an acetal ring in an α-position, the acetal ring is opened via an elimination reaction yielding unsaturated hydantoin derivatives.These reactions were studied using 1,2:5,6-di-O-isopropylidene-α-D-ribo-hexofuranos-3-ulose, 2,3:4,5-di-O-isopropylidene-D-arabinose, -D-ribose, and -D-xylose, 2,3:5,6-di-O-isopropylidene-α-D-mannofuranose, 1,2-O-isopropylidene-3-O-methyl-α-D-xylo-pentodialdo-1,4-mannofuranose, 1,2:3,4-di-O-isopropylidene-α-D-galacto-hexodialdo-1,5-pyranose, and 2,3:4,5-di-O-isopropylidene-β-D-arabino-hexosulo-2,6-pyranose.
- Kuszmann, Jaanos,Maatron-Mereesz, Magdolna,Jerkovich, Gyula
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p. 249 - 264
(2007/10/02)
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- Convenient One-Pot Conversion of Alcohols into Esters via Hemiacetal Intermediates
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A simple and efficient one-pot oxidative procedure, adaptable to a large scale, is described for the preparation of methyl esters from either primary alcohols or vic-diols.The aldehyde is generated by Swern or periodate oxidation, followed by bromine oxidation of the methyl hemiacetal formed in aqueous methanolic solution.
- Lichtenthaler, Frieder W.,Jarglis, Pan,Lorenz, Klaus
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p. 790 - 792
(2007/10/02)
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- Preparation of (4R,5S)-(5-methyl-2,2-dimethyl-1,3-dioxolane-4-ylmethyl)-phosphonium iodide. A synthetic approach to olguine: further model studies
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The enantiomerically pure title compound ((4R,5S)-(5-methyl-2,2-dimethyl-1,3-dioxolane-4-ylmethyl)-phosphonium iodide) has been synthesized starting from (R,R)-(+)-tartaric acid.The synthesis of an oliguine analog has been carried out.Attempts have been made to improve the stereoselectivity and yield of key steps.
- Valverde, Serafin,Herradon, Bernardo,Rabanal, Rosa M.,Martin-Lomas, Manuel
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p. 332 - 338
(2007/10/02)
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- A Mechanistic Study of the Photoreactions of Deoxy Iodo Sugars
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Quantum yields of 0.31, 3.7, and 1.1 have been determined for the photochemical disappearance in heptane of 6-deoxy-6-iodo-1,2:3,4-di-O-isopropylidene-α-D-galactopyranose (1), 3-deoxy-3-iodo-1,2:5,6-di-O-isopropylidene-α-D-allofuranose (2), and 3-deoxy-3-iodo-1,2:3,4-di-O-isopropylidene-α-D-glucofuranose (3), respectively.The major reaction for compounds 2 and 3 is epimerization at C-3, a reaction not observable for compound 1.Photochemical epimerization takes place in at least two ways.First, carbon-iodine bond homolysis followed by recombination of the radicalsproduced either regenerates the starting iodide or gives its C-3 epimer.Second, a chain reaction takes place in which the propagation step involves transfer of an iodine atom from the deoxy iodo sugar (2 or 3) to the carbon radical produced by carbon-iodine bond homolysis.In the presence of oxygen a new set of photoproducts is formed.These include enol esters, alcohols, and carbonyl compounds.
- Roth, Richard C.,Binkley, Roger W.
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p. 690 - 693
(2007/10/02)
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