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  • 1.
    Alam, Rauful
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Pilarski, Lukasz T.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Pershagen, Elias
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabo, Kalman J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stereoselective intermolecular allylic C-H trifluoroacetoxylation of functionalized alkenes2012In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 134, no 21, p. 8778-8781Article in journal (Refereed)
    Abstract [en]

    Pd-catalyzed allylic C-H trifluoroacetoxylation of substituted alkenes was performed using PhI(OCOCF3)(2) as the oxidant and acyloxy source. Trifluoroacetoxylation of monosubstituted cyclopentenes and cyclohexenes proceeds with excellent regio- and diastereoselectivity. Studies with one of the possible (eta(3)-allyl)Pd(II) intermediates suggest that the reaction proceeds via stereoselective formation of Pd(IV) intermediates and subsequent stereo- and regioselective reductive elimination of the product.

  • 2.
    Cumpstey, Ian
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Frigell, Jens
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Pershagen, Elias
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Akhtar, Tashfeen
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Moreno-Clavijo, Elena
    Robina, Inmaculada
    Alonzi, Dominic S.
    Butters, Terry D.
    Amine-linked diglycosides: Synthesis facilitated by the enhanced reactivity of allylic electrophiles, and glycosidase inhibition assays2011In: Beilstein Journal of Organic Chemistry, ISSN 2195-951X, E-ISSN 1860-5397, Vol. 7, p. 1-9Article in journal (Refereed)
    Abstract [en]

    Diglycose derivatives, consisting of two monosaccharides linked at non-anomeric positions by a bridging nitrogen atom, have been synthesised. Conversion of one of the precursor monosaccharide coupling components into an unsaturated derivative enhances its electrophilicity at the allylic position, facilitating coupling reactions. Mitsunobu coupling between nosylamides and 2,3-unsaturated-4-alcohols gave the 4-amino-pseudodisaccharides with inversion of configuration as single regio- and diastereoisomers. A palladium-catalysed coupling between an amine and a 2,3-unsaturated 4-trichloroacetimidate gave a 2-amino-pseudodisaccharide as the major product, along with other minor products. Derivatisation of the C=C double bond in pseudodisaccharides allowed the formation of Man(N4-6)Glc and Man(N4-6)Man diglycosides. The amine-linked diglycosides were found to show weak glycosidase inhibitory activity.

  • 3. Cumpstey, Ian
    et al.
    Frigell, jens
    Pershagen, Elias
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Alonzi, D.S.
    Butters, T.D.
    N-linked neodisaccharides: Synthesis facilitated by the enhanced reactivity of allylic electrophiles, and glycosidase inhibitory activityManuscript (preprint) (Other academic)
    Abstract [en]

    Neodisaccharides consisting of two monosaccharides linked by a bridging nitrogen atom have been synthesised. Converting one of the monosaccharide coupling components into an unsaturated derivative enhances its electrophilicity at the allylic position, facilitating coupling reactions. Mitsunobu coupling between nosylamides and 2,3-unsaturated 4-alcohols gave the 4-amino pseudodisaccharides with inversion of configuration as single regio- and diastereoisomers. A palladium catalysed coupling between an amine and a 2,3-unsaturated 4-trichloroacetimidate gave a 2-amino pseudodisaccharide as the major product along with other minor products. Derivatisation of the C=C double bond in pseudodisaccharides allowed the formation of Man(N4–6)Glc and Man(N4–6)Man neodisaccharides. The inhibitory activity of some N-linked neodisaccharides against the enzyme α-Glucosidase II is reported.

  • 4.
    Pershagen, Elias
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Development and applications of lanthanide-based luminescent probes2012Licentiate thesis, comprehensive summary (Other academic)
  • 5.
    Pershagen, Elias
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Nordholm, Johan
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Borbas, K. Eszter
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Luminescent Lanthanide Complexes with Analyte-Triggered Antenna Formation2012In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 134, no 24, p. 9832-9835Article in journal (Refereed)
    Abstract [en]

    A new strategy for accessing analyte-responsive luminescent probes is presented. The lanthanide luminescence of Eu and Tb centers is switched on by the analyte-triggered formation of a sensitizing antenna from a nonsensitizing caged precursor. As the cage can be freely varied, an array of probes for different analytes (pd(0/2+), H2O2, F-, beta-galactosidase) can be created from the same core structure. The probe design affords nanomolar to micromolar detection limits, provides the capability to detect two analytes in parallel, and can be utilized to monitor enzymatic activity in live cells.

  • 6. Szijjarto, Csongor
    et al.
    Pershagen, Elias
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Borbas, K. Eszter
    Functionalisation of lanthanide complexes via microwave-enhanced Cu(I)-catalysed azide–alkyne cycloaddition2012In: Dalton Transactions, ISSN 1477-9226, E-ISSN 1477-9234, Vol. 41, no 25, p. 7660-7669Article in journal (Refereed)
    Abstract [en]

    Cu-I-catalysed azide-alkyne cycloaddition reactions were used to functionalise lanthanide(III)-complexes (Ln; La, Eu and Tb) incorporating alkyne or azide reactive groups. Microwave irradiation significantly accelerated the reactions, enabling full conversion to the triazole products in some cases in 5 min. Alkyl and aryl azides and alkyl and aryl alkynes could all serve as coupling partners. These reaction conditions proved efficient for cyclen-tricarboxylates and previously unreactive cyclen-tris-primary amide chelates. The synthesis of heterobimetallic (Eu/Tb, EuTb17 and Eu/La, EuLa17) and heterotrimetallic (Eu/La/Eu) complexes was achieved in up to 60% isolated yield starting from coumarin 2-appended alkynyl complexes Tb16 or La16 and an azido-Eu complex Eu4, and bis-alkynyl La-complex La5 and Eu4, respectively. EuTb17 displayed dual Eu-III and Tb-III-emission upon antenna-centred excitation.

  • 7. Szijjarto, Csongor
    et al.
    Pershagen, Elias
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Uppsala University, Sweden.
    Ilchenko, Nadia O.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Borbas, K. Eszter
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Uppsala University, Sweden.
    A Versatile Long-Wavelength-Absorbing Scaffold for Eu-Based Responsive Probes2013In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 19, no 9, p. 3099-3109Article, review/survey (Refereed)
    Abstract [en]

    Coumarin-sensitized, long-wavelength-absorbing luminescent EuIII-complexes have been synthesized and characterized. The lanthanide binding site consists of a cyclen-based chelating framework that is attached through a short linker to a 7-hydroxycoumarin, a 7-B(OH)2-coumarin, a 7-O-(4-pinacolatoboronbenzyl)-coumarin or a 7-O-(4-methoxybenzyl)-coumarin. The syntheses are straightforward, use readily available building blocks, and proceed through a small number of high-yielding steps. The sensitivity of coumarin photophysics to the 7-substituent enables modulation of the antenna-absorption properties, and thus the lanthanide excitation spectrum. Reactions of the boronate-based functionalities (cages) with H2O2 yielded the corresponding 7-hydroxycoumarin species. The same species was produced with peroxynitrite in a x106107-fold faster reaction. Both reactions resulted in the emergence of a strong approximate to 407nm excitation band, with concomitant decrease of the 366nm band of the caged probe. In aqueous solution the methoxybenzyl caged Eu-complex was quenched by ONOO. We have shown that preliminary screening of simple coumarin-based antennae through UV/Vis absorption spectroscopy is possible as the changes in absorption profile translate with good fidelity to changes in EuIII-excitation profile in the fully elaborated complex. Taken together, our results show that the 7-hydroxycoumarin antenna is a viable scaffold for the construction of turn-on and ratiometric luminescent probes.

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