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  • 1.
    Buskas, Therese
    Stockholm University.
    Synthesis of lactosamine-containing carbohydrate structures and development for their easy assembly and conjugation1999Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is based on four publications. The first chapter describes preparation of anomerically pure thioethyl-, thiophenyl-, and n-pentenyl 2-azido-2-deoxy glycosyl building blocks from easily accessible per-acetylated glycosamines.

    In the second part, acetylated, benzylated and non-protected n-pentenyl glycosides are used as substrates for preparing various spacer functionalities, which are obtained by means of radical elongations, oxidations and reductions.

    The syntheses of a trisaccharide,a-D-GlcpNAc-(1-->4)-b-D-Galp-(1-->4)-b-D-GlcpNAc, and fragments thereof, linked to a long lipophilic aglycon, are described in the third part. For the formation of theb-D-Galp-(1-->4)-D-GlcpNAc bond, several differently protected glucosamine acceptors were prepared and their reactivity towards a disaccharide donor evaluated.

    Finally, lactosamine derivatives were prepared by regioselective galactosylation and used as building blocks in the chemical synthesis of various oligosaccharides. The syntheses of polylactosamine di-, tri- and tetramers were achieved by regioselective glycosylation. Also spacer containing sulfated N-acetyllactosamine and Lewis x structures were synthesised.

  • 2.
    Kers, Annika
    Stockholm University.
    Towards synthesis of biologically important phosphate analogues: exploring H-phosphonate and C-phosphonate chemistry1999Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is based on studies directed towards the development of methods for the preparation of phosphorus containing natural products, with the focus on C-phosphonate nucleic acid analogues.

    Mechanistic studies concerning formation of the phosphorus-carbon bond resulted in development of two efficient protocols for the synthesis of C-phosphonates from the corresponding H-phosphonate derivatives. These were applied, inter alia, to the synthesis of a novel type of nucleotide analogue containing the 4-pyridylphosphonate internucleotide bond. Also, synthesis of new nucleoside 5'-methylenephosphonate building blocks, suitable for incorporation into oligonucleotides or their conjugates, and a new method for the preparation of alkyl H-phosphonates, are discussed. Finally, mechanistic investigations related to C-phosphonates formation via N->C phosphorus migration in certain complexes of DBU with chlorophosphates, are presented.

  • 3.
    Kers, Inger
    Stockholm University.
    Nucleoside phosphoramidates and related compounds: development of synthetic methods based on H-phosphonate chemistry1999Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis, studies directed towards development of new synthetic methods for the preparation of nucleotide analogues of potential medical value as antisense, antigene or antiviral agents, are described.

    Two methods for synthesis of N3'->P5' and P3'->N5' phosphoramidate analogues with the nitrogen atom in bridging position of the internucleotide linkage was developed. Both of them make use of the readily available H-phosphonate monoesters as starting materials and permit the introduction of multiple modifications at the phosphorus center. In conjunction with these, a simple and efficient method for the preparation of nucleoside H-phosphonothioates, as a starting material for various phosphate analogues was also developed. As part of theses studies, base-induced disproportionation of aryl H-phosphonates was investigated.

    A new type of prodrugs for AZT, symmetrical phosphoramidates, have been synthesised as potential anti-retroviral agent.

  • 4.
    Lindström, Ulf M.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Somfai, Peter
    Microwave-assisted aminolysis of vinylepoxides1999In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 40, no 52, p. 9273-9276Article in journal (Refereed)
    Abstract [en]

    Di- and trisubstituted vinyl epoxides in NH4OH were subjected to microwave irradn. affording the corresponding vicinal amino alcs. in high yields. The reaction is stereospecific and highly regioselective for addn. at the allylic carbon. [on SciFinder(R)]

  • 5.
    Linnerborg, Malin
    Stockholm University.
    Structural elucidation of the O-antigen polysaccharides of five Escherichia coli strains1999Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The cell walls of bacteria are composed to a large extent of different polysaccharides. In order to understand and thereby, be able to utilise the physical, biological and immunological properties of polysaccharides, it is important to determine their structures. In the present thesis, structural investigations of the O-antigen polysaccharides from five strains of Escherichia coli, serogroups O138, O164, O167, O173 and O159, are described.

    Nuclear Magnetic Resonance (NMR) spectroscopy was the primary technique employed. Fast Atom Bombardment Mass Spectrometry (FAB-MS) and Electrospray Mass Spectrometry (ESI-MS) together with chemical degradations of the polysaccharides were also utilised.

    The possibilities, advantages and disadvantages of certain available methods for such studies are discussed.

  • 6.
    Pettersson, Ethel
    Stockholm University.
    Mechanism Studies of Catalytic RNA, and RNA and DNA Model Compounds1999Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes mechanism studies of transesterifications of phosphate esters. The aim of the studies concerns two fields. First, the catalytic mechanism that group I introns use in self-splicing. The focus was on metal ion coordinating groups at the catalytic site. Studies were performed on a (almost) full-length group I intron. A 2'-amino modification was introduced in the co-substrate and metal ion switch experiments were carried out. In the presence of magnesium ions the reaction rate decreased but introducing nitrogen preferring metal ions as for example manganese, this negative trend could be reversed. Further studies of the catalytic mechanism were performed on the same group I intron but converted to a ribozyme by deleting the substrate site. We introduced a 2'-amino group in the leaving group nucleoside, in a chemical synthesized substrate and metal ion switch experiments were carried out. At most we could study the cleavage reaction with two 2'-amino modifications at the catalytic site, in the co-substrate and in the substrate. In the presence of two 2'-amino modifications we obtained more than additive effects on the rate, in the presence of manganese ions. These experiments showed how one catalytic metal ion coordinated to the 2'-position in the co-substrate and a second one to the 2'-position in the leaving sugar nucleoside. An alternative model of the earlier proposed two metal ion mechanism used by group I introns, is presented.

    Five RNA model compounds, methyl furanosides with a 5-diphenyl phosphate group were synthesized. The metal ion promoted intramolecular cyclisation reaction, where the 3-hydroxyl attacks the 5-diphenyl phosphate was studied in the presence of different divalent metal ions. Two derivatives contained a 2-amino group and higher reaction rates were obtained in experiments with nitrogen preferring metal ions. These studies showed the effect of an adjacent position, on the hydroxy nucleophile, via coordination of a metal ion and also give data supporting the mechanism model for the catalytic RNA. The other field in this thesis concerns investigations on why ethylene oxide causes more DNA damages, than propylene oxide. To exclude that the intramolecular phosphate transesterification reaction was responsible for the observed differences, two dithymidine alkyl phosphates were synthesized and studied. Further, to see that the respective epoxide did not have different alkylation rates toward a phosphate center, the alkylation rate for the respective epoxide was studied. Neither of these events could be ascribed to be responsible for the earlier observations concerning ethylene oxide and propylene oxide.

  • 7.
    Söderman, Peter
    Stockholm University.
    Synthesis of oligosaccharides for structural, conformational and molecular recognition investigations1999Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Carbohydrates are involved cell-cell interaction. Synthesis of small and medium sized oligosaccharides is important to gain more understanding about the their physical properties that are crucial for their action in molecular recognition events. The first paper describes the synthesis, structural and conformational analysis of four different trisaccharides. The second paper describes a stereospecific synthesis of methyl a-(4-2H)-cellobioside, applying a regioselective oxidation stereospecific reduction sequence. In the third paper investigation of 1,3-dibromo-5,5-dimethylhydantoin in regioselective oxidation of stannylene acetals of different monosaccharide diols is described. The fourth study describes the synthesis of three different trisaccharides related to Escherichia coli O35 and Salmonella arizona O62, where the selective oxidation of a hydroxymethyl group using TEMPO is the key step. The last work summarize the synthesis of a model hexasaccharide from the core region of a Haemonchus contortus glycoprotein. The key steps in this synthesis are regioselective glucosidation to form a trisaccharide core followed by trifucosylation and conversion of a b-glucoside to the corresponding b-mannoside.

  • 8.
    Wachtmeister, Johanna
    Stockholm University.
    Synthesis of Potential Inhibitors Against HIV1999Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis describes the syntheses of various potential inhibitors of HIV, e.g. some 3´-hydroxymethyl-substituted carbocyclic nucleoside analogues as reverse transcriptase inhibitors and some symmetry-based peptidomimetics as protease inhibitors.

    Enantiomerically pure (3S,4S)-bis-(hydroxymethyl)cyclopentanone ethylene glycol ketal was used in the syntheses of eight functionalized cyclopentanol intermediates. These were either condensed with 6-chloropurine bases using the Mitsunobu reaction or converted into the corresponding cyclopentylamines, on which the purine bases were built up.

    The influence of the central hydroxyl groups on the anti-viral activity of L-mannaric acid based HIV-1 protease inhibitors was investigated. L-Iditol was used as the chiral precursor in the synthesis of the inhibitors with inverted configuration at C-3 and C-4.

    All target compounds described in this thesis were evaluated for anti-viral activity against the human immunodeficiency virus.

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