Structural variations of N-acetylneuraminic acid, 24: Synthesis of the α-methylketoside of 8-oxo-N-acetylneuraminic acid and related derivatives

The synthesis of the sodium 5-acetamido-2,3,5-trideoxy-2,3 didehydro-D-galacto-2,8-nondiulopyranosidonate 8,8-dimethyl acetal (8) and of the methyl-5-acetamido-3,5-dideoxy--D-galacto-2,8-nondiulopyranosidonate 8,8 dimethyl acetal (11) as well as of the methyl-5-acetamido-3,5-dideoxy--D-galacto-2,8-nondiulopyranosidonic acid (12) is reported involving the easily accessible 8-oxoderivative5. Compounds11 and12, respectively, showed to have glycosidic bond with remarkable stability to acidic conditions.

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Strukturelle Variationen an N-Acetylneuraminsäure, 24. Mitt.: Synthese des -Methylketosids von 8-Oxo-N-acetylneuraminsäure und verwandten Derivaten

Zusammenfassung Es wird ein Zugang zu Natrium-(5-acetamido-2,3,5-trideoxy-2,3-didehydro-D-galacto-2,8-nondiulopyranosid)onat-8,8-dimethylacetal (8), Methyl-5-acetamido-3,5-dideoxy--D-galacto-2,8-nondiulopyranosidonat-8,8-dimethyl acetal (11) und Methyl-5-acetamido-3,5-dideoxy--D-galacto-2,8-nondiulopyranosidonsäure (12) über ein gemeinsames, leicht herzustellendes 8-Oxo-Sialinsäurederivat5 beschrieben. Die glycosidische Bindung der Verbindungen11 bzw.12 zeigt eine bemerkenswerte Stabilität gegenüber sauren Reaktionbedingungen, welche im Gegensatz zu Beobachtungen an anderen Neuraminsäuremethylketosiden steht.

     

Synthesis of both enantiomers of methylenolactocin,nephrosterinic acid and protolichesterinic acid via tandem aldol–lactonization reactions

Both forms of the enantiomerically pure methylenolactocin, nephrosterinic and protolichesterinic acid have been synthesized via tandem aldol–lactonization reactions from corresponding optically active itaconate–anthracene adducts.     

The design and synthesis of a novel organophosphorus compound containing the structure of both β-amino acid and β-aminophosphonate

<正>A novel organophosphorus compound containing the structure of bothβ-amino acid andβ-aminophosphonate is designed and synthesized.Arbuzov reaction with P(OEt)_3,the N-Boc protected iodide 3 cannot provide the desired product but 2-oxazolidinone 4 because of the neighboring-group participation of the Boc moiety.To avoid the intramolecular participation of the carbamates,the Ts protecting group is employed and the Ts-protected iodide 5 affords the target product successfully.     

Diastereo- and enantioselective preparation of β-alkylhomoallylic alcohols : Synthesis of serricornin and corynomycolic acid

A new and efficient method for the preparation of four possible stereoisomers of β-alkylhomoallylic alcohols 1 has been developed which is based on the diastereoselective addition of nucleophiles to optically active α-alkyl-β-trimethylsilyl-β,γ-unsaturated carbonyl compounds. The utility of this reaction is demonstrated by the synthesis of naturally occurring serricornin and corynomycolic acid.     

Synthesis of novel β2,2-amino acid from D-mannose and attempted synthesis of peptides from the amino acid

The study describes the synthesis of new α,α-disubstituted β-amino acid (β^2,2-Caa) and attempts the synthesis of peptides from it. The β^2,2-Caa was prepared from D-(+)-mannose, using crossed aldol and Cannizzaro reactions.     

Synthesis of new β- and γ-benzyloxy-S-glutamic acid derivatives and evaluation of their activity as inhibitors of excitatory amino acid transporters

An efficient stereoselective preparation of the two enantiomerically pure diasteroisomers of γ-benzyloxy-S-glutamic acid was performed using trans-4-hydroxy-l-proline as a source of chirality, while the erythro and threo isomers of β-benzyloxy-S-glutamic acid were prepared starting from (R)-Garner's aldehyde. All new derivatives were tested for their inhibitory activity against excitatory amino acid transporters in a rat synaptosomal preparation and their IC₅₀ values were compared to that of TBOA, a one carbon lower homologue commonly used as the reference blocker of glutamate transporters.     

Synthesis of the β2-Agonist Tulobuterol and Its Metabolite 4-Hydroxytulobuterol

Russian Journal of Organic Chemistry - Alternative methods have been developed for the synthesis of the β2-agonist tulobuterol and its metabolite 4-hydroxytulobuterol with a similar activity....     

Synthesis and Conformational Analysis of 1, 2-Anhydro-3, 4-di-O-benzyl-6-deoxy-α-D-glucopyranose

Abstract

The title 1, 2-anhydro sugar (10) was synthesized from methyl 4, 6-O-benzylidene-α-D-glucopyranoside or from 1, 2-O-ethylidene-α-D-glucopyranose. The key intermediate for the synthesis was 2-O-acetyl-3, 4-di-O-benzyl-6-deoxy-β-D-glucopyranosyl fluoride (8)which was transformed into the target compound by ring closure with potassium tert-butoxide. Calculations by the modified Karplus equation from vicinal coupling constants of 10 suggested that the conformation of 10 was almost an ideal ⁴ H ₅ for the pyranose ring. Conformational analysis for the 1, 2-O-(R)-ethylidene intermediates 17 and 20 revealed that their pyranose ring basically adopted a B₂,₅ conformation.     

Synthesis of β-functionalized ethyl polyfluoroaryl sulfides, sulfoxides, and sulfones underlain by pentafluorobenzoic acid

The reaction of pentafluorobenzoic acid with 2-mercaptoethanol followed by modification of the reaction product by oxidationm halohydroxylation and (or) decarboxylation led to the formation of β-halo- and β-oxyethyl polyfluoroaryl sulfides, sulfoxides, and sulfones, initial compounds for the synthesis of fluorinecontaining 2,3-dihydro-1,4-benzothiazines, 2,3-dihydro-1,4-benzoxathiynes, and 2,3-dihydro-1,4-benzodithiynes and also of their S-oxides and S-dioxides based on intramolecular nucleophilic sybstitution.     

Highly stereoselective reduction of chiral α-keto-β, γ-unsaturated acetals: Synthesis of both epimeric allyl alcohols by proper choice of additive

Highly stereoselective reduction of chiral α-keto-β, γ-unsaturated acetals (1a-3a) into each two epimeric optically active allyl alcohols (1b-3b and1c-3c) was attained by LiAlH₄ using additive (LiBr, MgBr₂).     

Reaction of CH acids with 2-arylidenecycloalkanones: Synthesis of β-keto acid anilide derivatives of naphthalene,indene, fluorene,and phenanthrene

Summary 2-Arylidene-cyclohexanone1, -cyclopentanone2, -1-indanone3 and-1-tetralone4 react with acetoacetanilide5 yielding 2-oxo-4-aryl-3-carboxylic acid anilides derivatives of naphthalene7, indene8, fluorene9 and phenanthrene10. Reaction of1 and3 with benzoylacetanilide6 yields the corresponding Michael adducts11 and12.

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Reaktion von CH-Säuren mit 2-Arylidencycloalkanonen. Synthese von -Ketosäureanilid-Derivaten von Naphthalin, Inden, Fluoren und Phenanthren

Zusammenfassung 2-Arylidencyclohexanone1, -cyclopentanone2, -1-indanone3 und -1-tetralone4 reagieren mit Acetoacetanilid5 unter Bildung von 2-Oxo-4-aryl-3-carbonsäureanilid-Derivaten von Naphthalin7, Inden8, Fluoren9 und Phenanthren10. Die Reaktion von1 und3 mit Benzoylacetanilid6 ergibt die entsprechenden Michael-Addukte11 und12.

     

Synthesis and resolution of β2,2-HBin,the first enantiomerically stable β-amino acid with chirality only due to axial dissymmetry

The first gem-disubstituted β^2,2-amino acid possessing only axial chirality, was synthesized by bis-alkylation of methyl or ethyl cyanoacetate with both racemic and enantiomerically pure (R)-2,2′-bis-(bromomethyl)-1,1′-binaphthyl, followed by NaBH₄/CoCl₂ reduction of the cyano group, treatment of the resulting amino esters with Boc₂O and finally saponification of the ester function, to afford the C- and/or N-protected derivatives of 2′,1′:1,2;1′′,2′′:3,4-dinaphthcyclohepta-1,3-diene-6-aminomethyl-6-carboxylic acid: (RS)- and (R)-X-β^2,2-HBin-OR (X=Boc; H) (R=Me, Et or H). For the medium-scale resolution of β^2,2-HBin, the racemic amino esters (RS)-H-β^2,2-HBin-OR (R=Me, Et) were treated with benzoic anhydride and the resulting derivatives (RS)-Bz-β^2,2-HBin-OR were saponified. The obtained (RS)-Bz-β^2,2-HBin-OH was coupled with l-phenylalanine cyclohexylamide by the EDC/HOBt method to afford the dipeptide diastereoisomers Bz-(R)-Bin-l-Phe-NH-C₆H₁₁ and Bz-(S)-Bin-l-Phe-NH-C₆H₁₁, which were separated by chromatography. Complete hydrolysis under acidic conditions, followed by esterification of the resulting free amino acid enantiomers, N-protection and saponification, led to the enantiomerically pure derivatives (R)- and (S)-X-β^2,2-HBin-OR (X=Boc; H) (R=Me, H).     

Synthesis of Substituted γ-Butyrolactones: β-Hydroxymethyl-, β-Methylene and Cyclopropane Derivatives

A β-hydroxymethyl-γ-butyrolactone, which is a useful intermediate for the synthesis of several natural products with biological activity, was synthesized with good yield and a reduced number of steps from simple commercially available starting materials. Model compounds of natural products containing the unsaturated γ-butyrolactone unit, such as butenolides and β-methylene-γ-butyrolactones, were also conveniently synthesized from this hydroxymethyl-lactone.     

Synthesis of a Novel Core-shell Type Acrylic-polyurethane Hybrid Emulsion Containing Siloxane and Fluorine as well as Water and the Oil Resistances of Cured Film

Aqueous acrylic-polyurethane dispersions have become one of the major types of materials used in coating, paint and adhesive industries, because of excellent properties and environmental advantages1-5. However, some properties for cured film such as water…     

Synthesis, Structure and Transesterification of the Derivatives of β-Alkoxycarbonylethyltin Trichlorides with Diethyldithiocarbamate

o-Alkoxycarbonylethyltintrichlorides,RoCOCH2CH,SnCl,l,anovelmpeofmono-organotincompoundscontainingestergroup,havereceivedconsiderableattentionsinceHuttonetalreportedtheirSynthesis"'.Theirspectr8ldareshowedthatthecentCrtinatomwaspenta-coordinatedwithintramolecularestCrcarbonyloxygentotincoordinationandtheintramolecularcoordinationcanbebrokenbyextemalbidentatedonor,suchas2,2'-bipyridyI,l,1o-phenanthroline,etc.'-'.TheaddqctSoflwithneutraldonor,forexample,dimethylsulfoxide,hexamethylphosphor…     

Synthesis, characterisation and photo-stability of a folate-modified β-cyclodextrin as a functional food additive

A novel two-step synthetic route was developed and gave the mono-substituted derivative 6-deoxy-6-[(1-(2-amino)ethylamino)folate]-β-cyclodextrin (CDEnFA) with high yield (60?%). Elemental analysis, mass spectrometry, ¹H and ¹³C NMR, FTIR and Raman spectroscopies demonstrated the successful synthesis of the γ isomer only with no evidence of the presence of other isomers or free folic acid. Electronic absorption spectroscopy was used to study the photochemical properties of CDEnFA and showed that in both the solid state and aqueous solution CDEnFA is considerably more photo-stable than free folic acid.     

Synthesis and characterization of a novel Fe3O4@SiO2/bipyridinium dichloride nanocomposite and its application as a magnetic and recyclable phase-transfer catalyst in the preparation of β-azidoalcohols, β-cyanohydrins,and β-acetoxy alcohols

β-Azidoalcohols, β-cyanohydrins, and β-acetoxy alcohols have been synthesized in the presence of a Fe₃O₄@SiO₂/bipyridinium nanocomposite (Fe₃O₄@SiO₂/BNC) as a novel magnetic and recyclable phase-transfer catalyst (PTC) in water. The catalyst was characterized with FT–IR, SEM, XRD, VSM, and TGA. This methodology offers several advantages, including easy work-up procedure, excellent regioselectivity, high yields, short reaction times, recyclable catalyst, easy separation of the catalyst through an external magnet and eco-friendly procedure.