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  • 2601.
    Zaccheus, Mona
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Pendrill, Robert
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Jackson, Trudy A.
    Wang, An
    Auzanneau, France-Isabelle
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Conformational Dynamics of a Central Trisaccharide Fragment of the LeaLex Tumor Associated Antigen Studied by NMR Spectroscopy and Molecular Dynamics Simulations2012In: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, no 25, p. 4705-4715Article in journal (Refereed)
    Abstract [en]

    Certain carbohydrate structures are recognized as cancer antigens, and identification of these and relevant epitopes are essential in fighting the disease. The trisaccharide beta-D-GlcpNAc-(1?3)-beta-D-Galp-(1?4)-beta-D-GlcpNAc-OMe represents a model for the central region of the LeaLex hexasaccharide and it has herein been investigated by 1D 1H,1H-NOESY experiments to obtain effective interresidue protonproton distances as well as by 2D J-HMBC experiments to determine transglycosidic 3JCH coupling constants. Molecular dynamics (MD) simulations using explicit water as solvent and three different carbohydrate force fields, namely, GLYCAM06, PARM22/SU01, and CHARMM2011, were employed for the interpretation of experimental data. Overall, the force field based MD simulations are able to reproduce the experimental data and the ? torsion angle at the beta-(1?3)-linkage is concluded to be flexible. In addition, different minor states were present for the three force fields with either anti-? or non-exo-anomeric conformations. Transitions between the exo-anomeric and the non-exo-anomeric conformations for the f torsion angle at the beta-(1?4)-linkage in one of the MD simulations were analyzed in detail. It was found that hydrogen-bonding water molecules, interresidue hydrogen bonds and the transitions between antiperiplanar and synperiplanar conformations for the tH torsion angle of an N-acetyl group were all essential in the description of the glycosidic transition process. In particular, the transition of tH may be a general way of regulating other transitions into less populated but biologically important conformational regions.

  • 2602.
    Zaccheus, Mona V.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ali, Tara
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Cloeckaert, Axel
    Zygmunt, Michel S.
    Weintraub, Andrej
    Iriarte, Maite
    Moriyon, Ignacio
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    The Epitopic and Structural Characterization of Brucella suis Biovar 2 O-Polysaccharide Demonstrates the Existence of a New M-Negative C-Negative Smooth Brucella Serovar2013In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 8, no 1, p. e53941-Article in journal (Refereed)
    Abstract [en]

    The brucellae are Gram-negative bacteria that cause an important zoonosis. Studies with the main Brucella species have shown that the O-antigens of the Brucella smooth lipopolysaccharide are alpha-(1 -> 2) and alpha-(1 -> 3)-linked N-formyl-perosamine polysaccharides that carry M, A and C (A = M, A>M and A<M) epitopes relevant in serodiagnosis and typing. We report that, in contrast to the B. suis biovar 1 O-antigen used as a reference or to all described Brucella O-antigens, B. suis biovar 2 O-antigen failed to bind monoclonal antibodies of C (A = M), C (M>A) and M specificities. However, the biovar 2 O-antigen bound monoclonal antibodies to the Brucella A epitope, and to the C/Y epitope shared by brucellae and Yersinia enterocolitica O:9, a bacterium that carries an N-formyl-perosamine O-antigen in exclusively alpha-(1 -> 2)-linkages. By C-13 NMR spectroscopy, B. suis biovar 1 but not B. suis biovar 2 or Y.enterocolitica O:9 polysaccharide showed the signal characteristic of alpha-(1 -> 3)-linked N-formyl-perosamine, indicating that biovar 2 may altogether lack this linkage. Taken together, the NMR spectroscopy and monoclonal antibody analyses strongly suggest a role for alpha-(1 -> 3)-linked N-formyl-perosamine in the C (A = M) and C (M>A) epitopes. Moreover, they indicate that B. suis biovar 2 O-antigen lacks some lipopolysaccharide epitopes previously thought to be present in all smooth brucellae, thus representing a new brucella serovar that is M-negative, C-negative. Serologically and structurally this new serovar is more similar to Y. enterocolitica O:9 than to other brucellae.

  • 2603.
    Zaccheus, Mona V.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Broeker, Nina K.
    Lundborg, Magnus
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Uetrecht, Charlotte
    Barbirz, Stefanie
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Structural studies of the O‐antigen polysaccharide from Escherichia coli TD2158 having O18 serogroup specificity and aspects of its interaction with the tailspike endoglycosidase of the infecting bacteriophage HK6202012In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 357, p. 118-125Article in journal (Refereed)
    Abstract [en]

    We have analyzed the O-antigen polysaccharide of the previously uncharacterized Escherichia coli strain TD2158 which is a host of bacteriophage HK620. This bacteriophage recognizes and cleaves the polysaccharide with its tailspike protein (TSP). The polysaccharide preparation as well as oligosaccharides obtained from HK620TSP endoglycosidase digests were analyzed with NMR spectroscopy. Additionally, sugar analysis was performed on the O-antigen polysaccharide and MALDI-TOF MS was used in oligosaccharide analysis. The present study revealed a heterogeneous polysaccharide with a hexasaccharide repeating unit of the following structure: α-D-Glcp-(1→6|) →2)-α-L-Rhap-91→6)-α-D-Glcp-(1→4)-α-D-Ga|lp-(1→3)-α-D-GlcpNAc-(1→ β-D-Glcp/β-D-GlcpNAc-(1→3) A repeating unit with a D-GlcNAc substitution of D-Gal has been described earlier as characteristic for serogroup O18A1. Accordingly, we termed repeating units with D-Glc substitution at D-Gal as O18A2. NMR analyses of the polysaccharide confirmed that O18A1- and O18A2-type repeats were present in a 1:1 ratio. However, HK620TSP preferentially bound the D-GlcNAc-substituted O18A1-type repeating units in its high affinity binding pocket with a dissociation constant of 140 μM and disfavored the O18A2-type having a β-D-Glcp-(1→3)-linked group. As a result, in hexasaccharide preparations, O18A1 and O18A2 repeats were present in a 9:1 ratio stressing the clear preference of O18A1-type repeats to be cleaved by HK620TSP.

  • 2604.
    Zain, Rula
    Stockholm University, Faculty of Science.
    Nucleoside H-phosphonothioates: synthesis, oxidation and ³¹P NMR studies1995Doctoral thesis, comprehensive summary (Other academic)
  • 2605.
    Zalubovskis, Raivis
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Flexibility – a tool for chirality control in asymmetric catalysis2006Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    This thesis deals with the design and synthesis of ligands for asymmetric catalysis: palladium catalyzed allylic alkylations, and rho-dium and iridium catalyzed hydrogenations of olefins.

    Chirally flexible phosphepine ligands based on biphenyl were synthesized and their properties were studied. The rotation barrier for configurationally flexible phosphepines was determined by NMR spectroscopy. The ratio of the atropisomers was shown to depend on the group bound to phosphorus. Only complexes with two homochiral ligands bound to the metal center were observed upon complexation with Rh(I). It was shown that one diastereomer of the flexible ligand exhibits higher activity but lower selectivity than its diastereomer in the rhodium catalyzed hydrogenation of methyl alfa-acetamidocinnamate. These ligands were also tested in nickel catalyzed silabora-tions.

    Chiral P,N-ligands with pseudo-C2 and pseudo-CS symmetry based on pyrrolidines-phospholanes or azepines-phosphepines were synthesized and studied in palladium catalyzed allylic alkylations. Semi-flexible azepine-phosphepine based ligands were prepared and their ability to adopt pseudo-C2 or pseudo-CS symmetry depending on the substrate in allylic alkylations was studied. It was shown on model allyl systems with flexible N,N-ligands that the ligand prefers CS-symmetry in compexes with anti-anti as well as syn-syn allyl moieties, but that for the latter type of complexes, according to computations, the configuration of the ligand is R*,R* in the olefin complexes formed after addition of a nucleophile to the allylic group.

    A preliminary investigation of the possibilities to use a su-pramolecular approach for the preparation of P,N-ligands with pseudo-C2 and pseudo-S symmetry was made. An N,N-ligand with C2 symmetry was prepared and its activity in palladium catalyzed ally-lic alkylation was studied.

    Pyridine-based P,N-ligands were tested in iridium catalyzed hy-drogenations of unfunctionalized olefins with good activities and se-lectivities. In order to attempt to improve the selectivity, ligands with a chirally flexible phosphepine fragment were prepared and applied in catalysis with promising results.

  • 2606.
    Zalubovskis, Raivis
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Bouet, Alexis
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Fjellander, Ester
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Constant, Samuel
    University of Geneva.
    Linder, David
    University of Geneva.
    Andreas, Fischer
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry (closed 20110630).
    Lacour, Jérôme
    University of Geneva.
    Privalov, Timofei
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Self-adaptable Catalysts: Substrate-Dependent Ligand Configuration2008In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 130, no 6, p. 1845-1855Article in journal (Refereed)
    Abstract [en]

    Pd(II) allyl and Pd(0) olefin complexes containing the configurationally labile ligand 1,2-bis-[4,5dihydro-3H-dibenzo[c-e]azepino]ethane were studied as models for intermediates in Pd-catalyzed allylic alkylations. According to NMR and DFT studies, the ligand prefers C-s conformation in both eta(3)-1,3-diphenylpropenyl and eta(3)-cyclohexenyl Pd(II) complexes, whereas in Pd(0) olefin complexes it adopts different conformations in complexes derived from the two types of allyl systems in both solution and, as verified by X-ray crystallography, in the solid state. These results demonstrate that the Pd complex is capable of adapting its structure to the reacting substrate. The different structural preferences also provide an explanation for the behavior of 1,3-diphenyl-2-propenyl acetate and 2-cyclohexenyl acetate in Pd-catalyzed allylic alkylations using pseudo-C-2 and pseudo-C-s symmetric ligands.

  • 2607.
    Zalubovskis, Raivis
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Fjellander, Ester
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Szabó, Zoltán
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Stereochemical Control of Chirally Flexible Phosphepines2007In: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, Vol. 2007, no 1, p. 108-115Article in journal (Refereed)
    Abstract [en]

    The barriers to interconversion of the two enantiomeric atropisomers of 6-methoxy-6,7-dihydro-5H-dibenzo[c,e]phosphepine and that of the diastereomeric forms of 6-(-)menthoxy-6,7-dihydro-3H-dibenzo[c,e]phosphepine were determined by NMR spectroscopical methods to be 19.3 and 18.5 kcalmol(-1), respectively, at 298 K. The ratio of the atropisomers was shown to depend on the group bound to phosphorus. Only complexes with two homochiral ligands bound to the each metal center were obtained upon reaction with [Rh(COD)(2)](+) BF4-. The Rh complexes catalyzed the hydrogenation of alpha-acetamidocinnamate. The major isomer of 6-(-)-menthoxy-6,7-dihydro-5H-dibenzo[c,e]phosphepine was found to exhibit higher activity but to afford a product with lower ee than its diastereomer.

  • 2608.
    Zamaratski, Edouard
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Bioorganic Chemistry.
    Some Aspects of Nucleic Acids Chemistry2000Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is divided into two parts based on a total of 8 papers: Part 1: Synthesis, physicochemical and biochemical studies of chemically modified oligonucleotides and their duplexes and triplexes. Potency of the chromophore conjugated DNA oligonucleotides as antigene and antisense gene repressors was evaluated. The effect of geometry, bulk and ¥ð-electron density of a series of chromophores, tethered at the 5'-end of oligonucleotides, as well as the effect of the linker nature, length and the attachment site of the chromophore to the oligo were explored based on the stability of the duplexes and triplexes. A dramatic improvement in the triplex stability with ara-U linked phenazine oligo (potent antigene) was achieved (¥ÄTm = 16.5¢ª C). A number of selected phenazine and dipyridophenazine tethered antisense oligos (AONs) and their phosphorothioate analogues were shown to form the AON/RNA hybrid duplexes with enhanced thermal stability. CD experiments revealed that these duplexes have the global structure unaltered from that of the native counterpart. RNase H degradation studies on three RNA targets having different degrees of folded structures showed that tethering of phenazine and dipyridophenazine increases the hydrolysis rates (potent antisense) of the target RNA, and that chemical nature of the chromophore influences the RNase H cleavage pattern. Further investigation at the RNA saturated conditions revealed that 3'-tethered chromophores influence the substrate recognition, and the kinetics of the cleavage by RNase H. Conjugation of different chromophores, charged polyaromatic systems and metal complexes with polyaromatic ligands at different sites of the AON revealed that RNase H is very sensitive to any modifications in the middle region of the AON/RNA duplex. On the contrary, any modification at the 3'-end of the AON regardless of the bulk of the substituent or presence of positive charge can be easily tolerated by the enzyme. Sensitivity of the RNase H towards the local structural changes in the AON/RNA hybrid was probed with a number of AONs containing a single 1-(1',3'-O-anhydro-©¬-D-psicofuranosyl)thymine with locked 3'-endo sugar conformation at different sites of AON. RNase H degradation studies revealed that the local conformational changes brought by the constrained nucleoside, although invisible by CD, span in the hybrid as far as 5 nucleotides toward the 5'-end of the AONs (3'-end of RNA), showing the unique transmission of the structural distortion from a single modification site. The results also showed that the structural requirements for the substrate binding and substrate cleavage by RNase H appear to be different. Part 2: Preparation of biologically important isotope labelled oligo-RNAs for the NMR structure determination in solution. Synthesis of the non-uniformly 13C5 labelled 29mer HIV-1 TAR RNA was achieved by solid-phase synthesis using 13C5 labelled ribonucleosides from 13C6-D-glucose). Two hammerhead forming RNAs (16mer and 25mer) were synthesized according to the Uppsala NMR-window strategy, where the sugar residues of the nucleosides forming stem I, II and the loop of the stem III of the resulting hammerhead complex were deuterated. UV melting and high resolution NMR structural studies showed that the 16mer RNA under quasiphysiological condition folds to a very stable hairpin structure, which prevents formation of a hammerhead RNA with the 25mer, primarily owing to thermodynamic reasons.

  • 2609.
    Zeng X., Thibblin A.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry.
    Competing base-promoted E2 and E1 reactions of an acidic tertiary substrate2002In: J. Chem. Soc., Perkin Trans 2, p. 1352-Article in journal (Refereed)
  • 2610.
    Zeng, Xiaofeng
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry, Organic Chemistry.
    Mechanisms for Solvolytic Elimination and Substitution Reactions Involving Short-lived Carbocation Intermediates2002Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Solvolysis reactions of a range of tertiary substrates in largely aqueous solvents were studied in such respects as β-deuterium kinetic isotope effects, linear free energy relationships and stereochemistry.

    Solvolysis of the fluorene derivatives 9-methyl–9-(2´-X-2´-propyl)fluorene (1-X, X = Cl, Br, OOCCF3) involves a very short-lived carbocation intermediate. The fraction of alkene is increased by addition of general bases, which can be expressed by a Brφnsted parameter β = 0.07. The kinetic deuterium isotope effects vary with solvent composition in a way which is not consistent with a common carbocation intermediate which has time to choose between dehydronation and addition of a solvent water molecule.

    In the absence of bases, the reaction of 4-chloro-4-(4´-nitrophenyl)pentan-2-one (2-Cl) proceeds through a short-lived carbocation intermediate yielding 4-(4´-nitrophenyl)-2-oxopent-4-ene (2-t-ne)as the main elimination product. Addition of acetate ion and other weak bases results in the base-promoted E2 (or E1cb) reaction to give (E)-4-(4´-nitrophenyl)-2-oxopent-3-ene (2-E-ne) and (Z)-4-(4´-nitrophenyl)-2-oxopent-3-ene(2-Z-ne). There is no evidence for a water-promoted E2 (or E1cb) reaction.

    The stereochemistry studies of elimination from (R,S and S,R)-[1-(3´-fluoro)phenyl-2-methyl]cyclopentyl-p-nitrobenzoate (3-PNB) and its (R,R and S,S)isomer 3´-PNB and (R,S and S,R)-[1´-(3´´-fluoro)phenyl-2´-methylcyclopentyl]-2,2,2-trifluoroacetate(3-OOCCF3) exclude the concerted pericyclic elimination mechanism for formation of the alkene 1-(3´-fluoro)phenyl-2-methylcyclopentene(3-m-ne). The effects of added thiocyanate ion and halide ions on the solvolysis reaction are discussed.

    Mass spectrometry analysis showed complete incorporation of the labeled oxygen from solvent water into the product 2-hydroxy-2-phenyl-3-butene (4-OH), confirming that it is the tertiary carbon-oxygen bond that is broken in the acid-catalyzed solvolysis of 2-methoxy-2-phenyl-3-butene (4-OMe). The mechanism for the dominant formation of the less stable 4-OH is discussed.

  • 2611.
    Zetterström, Susanna
    Linköping University, Department of Physics, Chemistry and Biology, Organic Chemistry. Linköping University, The Institute of Technology.
    Isolation and synthesis of curcumin2012Independent thesis Basic level (degree of Bachelor), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    The aim of this thesis was to evaluate pre-existing methods for isolation and synthesis of curcumin. Two different isolation methods were used, where only the extraction step differs from each other. To obtain pure curcumin, column chromatography was needed to separate the compound from its analogues. As for the isolation the synthesis was also carried out by two different methods, the first in a conventional way and the second one by using irradiation of microwaves.

    The result of the experiments shows that by comparing the effectiveness and expense of the methods, the synthesis would probably be the easiest way of obtaining pure compound. Because of the more straightforward method, without cumbersome separation steps from the curcumin analogues, the synthesis was a faster way of obtaining the compound and gave more pure curcumin than the isolation procedures from turmeric.

  • 2612.
    Zhang, Jin
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Kamstra, Jorke H.
    Ghorbanzadeh, Mehdi
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Weiss, Jana M.
    Hamers, Timo
    Andersson, Patrik L.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    In Silico Approach To Identify Potential Thyroid Hormone Disruptors among Currently Known Dust Contaminants and Their Metabolites2015In: Environmental Science and Technology, ISSN 0013-936X, E-ISSN 1520-5851, Vol. 49, no 16, p. 10099-10107Article in journal (Refereed)
    Abstract [en]

    Thyroid hormone disrupting chemicals (THDCs) interfere with the thyroid hormone system and may induce multiple severe physiological disorders. Indoor dust ingestion is a major route of THDCs exposure in humans, and one of the molecular targets of these chemicals is the hormone transporter transthyretin (TTR). To virtually screen indoor dust contaminants and their metabolites for THDCs targeting TTR, we developed a quantitative structure activity relationship (QSAR) classification model. The QSAR model was applied to an in-house database including 485 organic dust contaminants reported from literature data and their 433 in silico derived metabolites. The model predicted 37 (7.6%) dust contaminants and 230 (53.1%) metabolites as potential TTR binders. Four new THDCs were identified after testing 23 selected parent dust contaminants in a radio-ligand TTR binding assay; 2,2',4,4'-tetrahydroxybenzophenone, perfluoroheptanesulfonic acid, 3,5,6-trichloro-2-pyridinol, and 2,4,5-trichlorophenoxyacetic acid. These chemicals competitively bind to TTR with 50% inhibition (IC50) values at or below 10 mu M. Molecular docking studies suggested that these THDCs interacted similarly with TTR via the residue Ser117A, but their binding poses were dissimilar to the endogenous ligand T4. This study identified new THDCs using an in silico approach in combination with bioassay testing and highlighted the importance of metabolic activation for TTR binding.

  • 2613. Zhang, Kai
    et al.
    Wei, Pingchun
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Xie, Yongshu
    Oxidative Ring Closure and Metal Triggered Ring Opening: Syntheses of Macrocyclic and Linear Hexapyrroles2014In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 16, no 24, p. 6354-6357Article in journal (Refereed)
    Abstract [en]

    A C6F5-substituted hexapyrrane (1) was synthesized in one step. Oxidative cyclization of 1 with DDQ afforded a phlorindipyrrin conjugate (2), and subsequent FeCl3-assisted oxidative cleavage of 2 afforded a terminally di-a-methoxy substituted hexapyrrin (3). On the other hand, oxidation of 1 with FeCl3 afforded 3, a hexapyrrinone Fe3+ complex (4), and a hexaphyrin (1,1,1,1,1,0) (5). These results indicate that the oxidation of hexapyrranes may be developed as an effective approach for the syntheses of novel linear and macrocyclic hexapyrroles.

  • 2614. Zhang, Kai
    et al.
    Zhang, Junda
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Guo, Rui
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ou, Zhongping
    Ishida, Masatoshi
    Furuta, Hiroyuki
    Xie, Yongshu
    Synthesis of a Neo-Confused Octaphyrin and the Formation of Its Mononuclear Complexes2015In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 17, no 19, p. 4806-4809Article in journal (Refereed)
    Abstract [en]

    Novel neo-confused octaphyrin(1.1.1.1.1.1.1.0) (1) was synthesized by oxidative ring closure of an octapyrrane bearing two terminal "confused" pyrroles. Crystal structures of its Zn(II) and Cu(II) complexes (2 and 3) show a figure-of-eight conformation with unique mononuclear coordination structures. Photophysical data and theoretical calculations suggest that the neo-confused octaphyrin 1 is a 34 pi electron conjugated species showing nonaromaticity. Coordination of pocopper and zinc ions results in the further narrowing of the HOMO-LUMO gaps.

  • 2615. Zhang, Meiling
    et al.
    Song, Ce
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Yao, Zhi
    Ji, Qiang
    Theoretical Studies of the Structure and Properties of Anticancer Drug Taxol2012In: Current organic chemistry, ISSN 1385-2728, E-ISSN 1875-5348, Vol. 16, no 19, p. 2321-2331Article in journal (Refereed)
    Abstract [en]

    In the present study, prior MD investigation or Monte-Carlo search, our step-by-step search for the real lowest energy conformers and the properties of taxol (Also called paclitaxel) is presented theoretically. The paper completes the old paper of Ballone and Marchi (JPC A 1999) which carried out LDA calculations on taxol. A total of 216 initial trial structures were generated by all combinations of internal single-bond rotamers and optimized at the B3LYP/3-21G* level and further optimized at the B3LYP/6-311G* level. A total of 12 unique conformers are found, and their relative energies, dipole moments, rotational constants, zero point vibrational energy, and harmonic frequencies are determined. Their relative electronic energies were determined at the M06L/6-311G(2df,p) level. Combined with statistical mechanics principles, conformational distributions at various temperatures are computed. Characteristic H-bonding types are classified and demonstrated in the taxol structure. It is found that various hydrogen bonds (red shift H-bonding, blue-shifted H-bonding and dihydrogen bond) coexist in the title compound. The NBO analysis was performed showing the change of the charge and stereoelectronic effect of different radicals. The UV spectra of the lowest-lying conformer of taxol in methanol are investigated with the TD CAM-B3LYP/6-311+G(2df,p)calculations. The S0-S1, S0-S2, and S0-S3 excitations of taxol are mixed pi pi*/pi sigma*/n pi* transitions at 4.32, 5.02, and 5.13 eV, respectively. The theoretical IR spectrum and UV absorption spectrum of the taxol agree with the available experimental data of taxol very well. Calculations in the solution using SCRF/CPCM method at the M06L/6-311G(2df,p) level showing the hydrophobic nature of taxol.

  • 2616.
    Zhang, Suode
    et al.
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I. Avd för organisk kemi.
    Govender, Thavendran
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I. Avd för organisk kemi.
    Norström, Thomas
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I. Avd för organisk kemi.
    Arvidsson, Per
    Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Chemistry, Department of Chemistry. Department of Biochemistry and Organic Chemistry, Organic Chemistry I. Avd för organisk kemi.
    An Improved Synthesis of Fmoc-N-methyl-a-amino Acids2005In: J. Org. Chem., no 70, p. 6918-6920Article in journal (Refereed)
  • 2617.
    Zhang, Wei
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Bah, Juho
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Wohlfarth, Andreas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Franzen, Johan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    A Stereodivergent Strategy for the Preparation of Corynantheine and Ipecac Alkaloids, Their Epimers, and Analogues: Efficient Total Synthesis of ()- Dihydrocorynantheol, ()-Corynantheol, ()-Protoemetinol, ()- Corynantheal, ()-Protoemetine, and Related Natural and Nonnatural Compound2011In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 17, no 49, p. 13814-13824Article in journal (Refereed)
    Abstract [en]

    Abstract: Here we present a general and common catalytic asymmetric strategy for the total and formal synthesis of a broad number of optically active natural products from the corynantheine and ipecac alkaloid families, for example, indoloACHTUNGTRENUNG[2,3-a]- and benzo[a]quinolizidines. Construction of the core alkaloid skeletons with the correct absolute and relative stereochemistry relies on an enantioselective and diastereodivergent one-pot cascade sequence followed by an additional diastereodivergent reaction step. This allows for enantio- and diastereoselective synthesis of three out of four possible epimers of the quinolizidine alkaloids that begin from common and easily accessible starting materials by using a common synthetic route. Focus has been made on excluding protecting groups and limiting isolation and purification of synthetic intermediates. This methodology is applied in the total synthesis of the natural products ()-dihydrocorynantheol, ()-hirsutinol, ()-corynantheol, ()-protometinol, ()-dihydrocorynantheal, ()-corynantheal, ()-protoemetine, ()-(15S)-hydroxydihydrocorynantheol, and an array of their nonnatural epimers. The potential of this strategy is also demonstrated in the synthesis of biologically interesting natural product analogues not accessible through synthetic elaboration of alkaloid precursors available from nature, for example, thieno[3,2-a]quinolizidine derivatives. We also report the formal synthesis of (+)-dihydrocorynantheine, ()-emetine, ()-cephaeline, ()-tubulosine, and ()-deoxytubulosine.

  • 2618.
    Zhang, Wei
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Franzen, Johan.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Applied Physical Chemistry.
    Asymmetric catalytic synthesis of corynanthe and ipecac alkaloids2012In: Targets in Heterocyclic Systems: Chemistry and Properties / [ed] Orazio A. Attanasi; Domenico Spinelli, Societa Chimica Italiana , 2012, p. 31-55Chapter in book (Refereed)
    Abstract [en]

    Corynanthe and ipecac alkaloids constitute a large group of natural occurring alkaloids that demonstrate a vast variety of bioactivity and have a long history of usage as herbal drugs. Both the corynanthe and ipecac alkaloids share a common structural unit with a quinolizidine ring fused with a benzo- or indolo-group and three stereocentres wherein one is a ring-junction stereocentre. From synthetic point of view, these natural products represent an intriguing challenge and over the years several strategies toward the asymmetric total synthesis of corynanthe and ipecac alkaloids have been devised and the majority of these are target specific natural-pool based strategies. However, during the last few years, several efficient and diverse strategies based on asymmetric catalysis and one-pot cascade protocols as the key-steps have emerged. In this mini-review the attention is to give an overview of these strategies.

  • 2619.
    Zhang, Wei
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Franzén, Johan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Diverse Asymmetric Quinolizidine Synthesis: A Stereodivergent One-Pot Approach2010In: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 352, no 2-3, p. 499-518Article in journal (Refereed)
    Abstract [en]

    A diverse stereodivergent organocatalytic one-pot addition/cyclization/annulation sequence to optically active quinolizidine derivatives from easily available starting materials is presented. The one-pot sequence relies on a pyrrolidine-catalyzed enantioselective Conjugate addition of electron-deficient amide alpha-carbons to alpha,beta-unsaturated aldehydes, spontaneous hemiaminal formation and acid-catalyzed/mediated N-acyliminium ion cyclization to give the quinolizidine framework. Simple tuning of the reaction conditions in the N-acyliminuim ion cyclization step provides a diastereomeric switch, which gives access to both of the two bridgehead epimers through kinetic, thermodynamic or chelation control. The methodology display a broad substrate scope that is demonstrated by the stereoselective formation of indolo-, thieno-, benzofuro-, furo- and different benzoquinolizidine derivatives with high atom efficiency, up to >99% ee and up to >95:5 dr. Due to its efficiency, synthetic diversity and operational simplicity, this protocol has the potential to find important use as a key step in natural product Synthesis, biochemistry and pharmaceutical science. The stereochemical Outcome of the one-pot sequence was investigated. and the mechanism and origin of stereoselectivity of the different steps is discussed.

  • 2620.
    Zhang, Yan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Chemoenzymatic Resolution in Dynamic Systems: Screening, Classification and Asymmetric Synthesis2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This  thesis  is  divided  into  four  parts,  all  centered  around  Constitutional Dynamic  Chemistry  (CDC)  and  Dynamic  Kinetic  Resolution  (DKR)  using biocatalysts for selective transformations, and their applications in screening of bioactive compounds, organic synthesis, and enzyme classification.   

    In  part  one,  an  introduction  to  CDC  and  DKR  is  presented,  illustrating  the basic  concepts,  practical  considerations  and  potential  applications  of  such dynamic systems, thus providing the background information for the studies in the following chapters.  

    In part two, Dynamic Systemic Resolution (DSR), a concept based on CDC is exemplified.  With  enzyme-catalyzed  transformations  as  external  selection pressure,  optimal  structures  can  be  selected  and  amplified  from  the  system. This  concept  is  expanded  to  various  types  of  dynamic  systems  containing single, double cascade/parallel, and multiple reversible reactions. In addition, the  substrate  selectivity  and  catalytic  promiscuity  of  target  enzymes  are  also investigated.  

    In   part   three,   DKR   protocols   using   reversible   reactions   for   substrate racemizations  are  illustrated.  Biocatalysts  are  here  employed  for  asymmetric transformations,  resulting  in  efficient  synthetic  pathways  for  enantioenriched organic compounds.  

    Part  four  demonstrates  two  unique  applications  of  CDC:  one  resulting  in enzyme  classification  by  use  of  pattern  recognition  methodology;  the  other involving  enzyme  self-inhibition  through  in  situ  transformation  of  stealth inhibitors employing the catalytic activity of the target enzyme.

  • 2621.
    Zhang, Yan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Hu, Lei
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Double parallel dynamic resolution through lipase-catalyzed asymmetric transformation2013In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 49, no 18, p. 1805-1807Article in journal (Refereed)
    Abstract [en]

    Dynamic systems based on double parallel reactions have been generated and resolved in situ by secondary lipase-catalyzed asymmetric transformation, resulting in high chemo- and enantioselectivities.

  • 2622.
    Zhang, Yan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Jayawardena, H. Surangi N.
    Yan, Mingdi
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. University of Massachusetts Lowell, MA, United States.
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Enzyme classification using complex dynamic hemithioacetal systems2016In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 52, no 28, p. 5053-5056Article in journal (Refereed)
    Abstract [en]

    A complex dynamic hemithioacetal system was generated for the evaluation of lipase reactivities in organic media. In combination with pattern recognition methodology, twelve different lipases were successfully classified into four distinct groups following their reaction selectivities and reactivities. A probe lipase was further categorized using the training matrix with predicted reactivity.

  • 2623. Zhang, Yan
    et al.
    Sakulsombat, Morakot
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Vongvilai, Pornrapee
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Hu, Lei
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Lipase-mediated dynamic systemic resolution based on single or double reversible reactions2012In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 244Article in journal (Other academic)
  • 2624.
    Zhang, Yan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Schaufelberger, Fredrik
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Sakulsombat, Morakot
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Liu, Chelsea
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Asymmetric synthesis of 1,3-oxathiolan-5-one derivatives through dynamic covalent kinetic resolution2014In: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 70, no 24, p. 3826-3831Article in journal (Refereed)
    Abstract [en]

    The asymmetric synthesis of 1,3-oxathiolan-5-one derivatives through an enzyme-catalyzed, dynamic covalent kinetic resolution strategy is presented. Dynamic hemithioacetal formation combined with intramolecular, lipase-catalyzed lactonization resulted in good conversions with moderate to good enantiomeric excess (ee) for the final products. The process was evaluated for different lipase preparations, solvents, bases, and reaction temperatures, where lipase B from Candida antarctica (CAL-B) proved most efficient. The substrate scope was furthermore explored for a range of aldehyde structures, together with the potential access to nucleoside analog inhibitor core structures.

  • 2625.
    Zhang, Yan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Zhang, Yang
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ren, Yansong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Synthesis of chiral oxazolidinone derivatives through lipase-catalyzed kinetic resolution2015In: Journal of Molecular Catalysis B: Enzymatic, ISSN 1381-1177, E-ISSN 1873-3158, Vol. 122, p. 29-34Article in journal (Refereed)
    Abstract [en]

    The synthesis of enantioenriched oxazolidinone derivatives through lipase-catalyzed kinetic resolution is described. The synthesis comprised a two-step, cascade acylation in one pot, resulting in a range of oxazolidinone derivatives in good yields and excellent enantiopurities.

  • 2626.
    Zhang, Yang
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Karalius, Antanas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Yan, Mingdi
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Kinetics and Thermodynamics of Dynamic Nitroaldol Systems in Neutral Aqueous MediaManuscript (preprint) (Other academic)
  • 2627.
    Zhang, Yang
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Xie, Sheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Yan, Mingdi
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Dynamic Covalent Chemistry of Aldehyde Enamines: Bi(III) and Sc(III) catalysis of amine-enamine exchangeManuscript (preprint) (Other academic)
  • 2628.
    Zhang, Yang
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Xie, Sheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Yan, Mingdi
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Enzyme- and Ruthenium-Catalyzed Dynamic Kinetic Resolution Involving Cascade Alkoxycarbonylations for Asymmetric Synthesis of 5-Substituted N-AryloxazolidinonesManuscript (preprint) (Other academic)
  • 2629.
    Zhang, Yang
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Zhang, Yan
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Xie, Sheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Yan, Mingdi
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Lipase-Catalyzed Kinetic Resolution of 3-Phenyloxazolidin-2-one Derivatives: CascadeO‐ and N‐AlkoxycarbonylationsManuscript (preprint) (Other academic)
  • 2630.
    Zhang, Yi
    et al.
    Capital Med Univ, Beijing Hosp Tradit Chinese Med, Dept Oncol, Beijing 100010, Peoples R China..
    Zhang, Gan-Lin
    Capital Med Univ, Beijing Hosp Tradit Chinese Med, Dept Oncol, Beijing 100010, Peoples R China..
    Sun, Xu
    Capital Med Univ, Beijing Hosp Tradit Chinese Med, Dept Oncol, Beijing 100010, Peoples R China..
    Cao, Ke-Xin
    Capital Med Univ, Beijing Hosp Tradit Chinese Med, Dept Oncol, Beijing 100010, Peoples R China..
    Shang, Ya-Wen
    Capital Med Univ, Sch Tradit Chinese Med, Beijing 100069, Peoples R China..
    Gong, Mu-Xin
    Capital Med Univ, Sch Tradit Chinese Med, Beijing 100069, Peoples R China..
    Ma, Cong
    Capital Med Univ, Beijing Hosp Tradit Chinese Med, Dept Oncol, Beijing 100010, Peoples R China..
    Nan, Nan
    Capital Med Univ, Beijing Hosp Tradit Chinese Med, Dept Oncol, Beijing 100010, Peoples R China..
    Li, Jin-Ping
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology. Capital Med Univ, Beijing Hosp Tradit Chinese Med, Dept Oncol, Beijing 100010, Peoples R China..
    Yu, Ming-Wei
    Capital Med Univ, Beijing Hosp Tradit Chinese Med, Dept Oncol, Beijing 100010, Peoples R China..
    Yang, Guo-Wang
    Capital Med Univ, Beijing Hosp Tradit Chinese Med, Dept Oncol, Beijing 100010, Peoples R China..
    Wang, Xiao-Min
    Capital Med Univ, Beijing Hosp Tradit Chinese Med, Dept Oncol, Beijing 100010, Peoples R China..
    Gubenyiliu II Inhibits Breast Tumor Growth and Metastasis Associated with Decreased Heparanase Expression and Phosphorylation of ERK and AKT Pathways2017In: Molecules, ISSN 1420-3049, E-ISSN 1420-3049, Vol. 22, no 5, article id 787Article in journal (Refereed)
    Abstract [en]

    Gubenyiliu II (GYII), a Traditional Chinese Medicine (TCM) formula used in our hospital, has shown beneficial effects in cancer patients. In this study, we investigated the molecular mechanisms underlying the beneficial effects of GYII on murine breast cancer models. GYII showed significant inhibitory effects on tumor growth and metastasis in the murine breast cancer model. Additionally, GYII suppressed the proliferation of 4T1 and MCF-7 cells in a dose-dependent manner. A better inhibitory effect on 4T1 cell proliferation and migration was found in the decomposed recipes (DR) of GYII. Moreover, heparanase expression and the degree of angiogenesis were reduced in tumor tissues. Western blot analysis showed decreased expression of heparanase and growth factors in the cells treated with GYII and its decomposed recipes (DR2 and DR3), and thereby a reduction in the phosphorylation of extracellular signal-regulated kinase (ERK) and serine-threonine kinase (AKT). These results suggest that GYII exerts anti-tumor growth and anti-metastatic effects in the murine breast cancer model. The anti-tumor activity of GYII and its decomposed recipes is, at least partly, associated with decreased heparanase and growth factor expression, which subsequently suppressed the activation of the ERK and AKT pathways.

  • 2631. Zhao, Dongbin
    et al.
    Fei, Zhaofu
    Ohlin, C. André
    Laurenczy, Gábor
    Dyson, Paul J.
    Dual-functionalised ionic liquids: synthesis and characterisation of imidazolium salts with a nitrile-functionalised anion2004In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, no 21, p. 2500-2501Article in journal (Refereed)
    Abstract [en]

    A series of ‘dual-functionalised’ ionic liquids, comprising imidazolium cations with various functionalities and the nitrile functionalised anion [CH3H(BF3)CH2CN](-) have been prepared; some exhibit very low viscosities-a highly valuable property in many applications.

  • 2632.
    Zhao, Gui-Ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Catalytic asymmetric Baylis–Hillman reactions and surroundings2010In: Catalytic Asymmetric Conjugate Reactions / [ed] Armando Córdova, Weinheim: Wiley-VCH Verlag GmbH & Co. KGaA , 2010, 1, p. 393-438Chapter in book (Other academic)
  • 2633.
    Zhao, Gui-Ling
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    ECAs of organolithium reagents, Grignard reagents, and examples of Cu-catalyzed ECAs2010In: Catalytic Asymmetric Conjugate Reactions / [ed] Armando Córdova, Weinheim: Wiley-VCH Verlag GmbH & Co. KGaA , 2010, 1, p. 145-167Chapter in book (Other academic)
  • 2634. Zhao, Gui-Ling
    et al.
    Córdova, Armando
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    ECAs of Organolithium reagents, Grignard reagents and Examples of Cu-Catalyzed ECAs2010In: Catalytic Asymmetric Conjugate Reactions, Wiley-VCH Verlagsgesellschaft, 2010Chapter in book (Refereed)
  • 2635.
    Zhao, Gui-Ling
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dziedzic, Pawel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ullah, Farman
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Department of Structural Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Organocatalytic enantioselective domino synthesis of highly functionalized cyclohexanes with an all-carbon quaternary stereocenter2009In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 50, no 26, p. 3458-3462Article in journal (Refereed)
    Abstract [en]

    A highly enantioselective organocatalytic domino Michael/aldol reaction is presented. The reaction is catalyzed by chiral amines and gives access to highly functionalized cyclohexanes with one all-carbon quaternary stereocenter and multiple chiral stereocenters in high yields and 83–98% ee.

  • 2636. Zhao, Gui-Ling
    et al.
    Hafrén, Jonas
    Deiana, Luca
    Córdova, Armando
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Heterogeneous “Organoclick” Derivatization of Polysaccharides: Photochemical Thiol-Ene Click Modification of Solid Cellulose2010In: Macromolecular rapid communications, ISSN 1022-1336, E-ISSN 1521-3927, Vol. 31, no 8, p. 740-744Article in journal (Refereed)
  • 2637.
    Zhao, Gui-Ling
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hafrén, Jonas
    Deiana, Luca
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Heterogeneous "organoclick" derivatization of polysaccharides: Photochemical thiol-ene click modification of solid cellulose2010In: Macromolecular rapid communications, ISSN 1022-1336, E-ISSN 1521-3927, Vol. 31, no 8, p. 740-744Article in journal (Refereed)
    Abstract [en]

    A simple and direct method for derivatization of solid polysaccharides is presented. The novel methodology is based on the combination of organic acid-catalyzed esterification or etherification and photochemical thiol-ene click derivatization of a heterogeneous polysaccharide. The solid cellulose was “organoclick” modified with aryl, alkyl and polyester groups, respectively. The modification allows for a highly modular and metal free surface modification of solid polysaccharides.

  • 2638.
    Zhao, Gui-Ling
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lin, Shuangzheng
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Korotvicka, Ales
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Deiana, Luca
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kullberg, Martin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Asymmetric synthesis of Maraviroc (UK-427,857)2010In: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 352, no 13, p. 2291-2298Article in journal (Refereed)
    Abstract [en]

    The asymmetric synthesis of Maraviroc (UK-427,857), a chemochine receptor 5 (CCR-5) receptor antagonist, based on an expeditious organocatalytic enantioselective assembly of the chiral β-amino aldehyde key fragment is presented. The reactions were performed on a gram-scale and allow for the rapid construction of new Maraviroc analogues.

  • 2639. Zhao, Gui-Ling
    et al.
    Ullah, Farman
    Deiana, Luca
    Lin, Shuangzheng
    Zhang, Qiong
    Sun, Junliang
    Ibrahem, Ismail
    Department of Organic Chemistry, The Arrhenius Laboratory, Stockholm University,.
    Dziedzic, Pawel
    Córdova, Armando
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Dynamic kinetic asymmetric transformation (DYKAT) by combined amine and transition metal catalyzed enantioselective cycloisomerization2010In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765Article in journal (Refereed)
  • 2640.
    Zhao, Gui-Ling
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ullah, Farman
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Luca, Deiana
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lin, Shuangzheng
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhang, Qiong
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Structural Chemistry.
    Ibrahem, Ismail
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dziedzic, Pawel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dynamic kinetic asymmetric transformation (DYKAT) by combined amine- and transition-metal-catalyzed enantioselective cycloisomerization2010In: Chemistry: a European Journal, ISSN 0947-6539, Vol. 16, no 5, p. 1585-1591Article in journal (Refereed)
  • 2641. Zhao, Jianghua
    et al.
    Yang, Xichuan
    Cheng, Ming
    Wang, Weihan
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. KTH, School of Chemical Science and Engineering (CHE), Centres, Centre of Molecular Devices, CMD.
    Influence of different methylene units on the performance of rhodanine organic dyes for dye-sensitized solar cells2014In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 4, no 10, p. 4811-4816Article in journal (Refereed)
    Abstract [en]

    In D-p-A structured organic dyes, rhodanine acetic acid and its derivates have served as electron acceptors successfully. In this work, two single rhodanine organic dyes with different methylene units have been synthesized and applied in dye-sensitized solar cells (DSSCs). The photophysical, electrochemical and photovoltaic properties have been studied systematically. The results show that dye with double methylene units produces a higher photon-to-electron conversion efficiency (eta) of 4.5% than that of a single methylene unit dye with a eta of 4.1%. Also, it is interesting to notice that the lengthened distance between electron acceptor and TiO2 surface does not decrease the short-circuit current density (J(sc)) and IPCE response for both structured dyes. On the contrary, rhodanine dye bearing double methylene units exhibits a better J(sc) and IPCE response than the single methylene unit. The explanation for this trend is probably due to the fact that increased methylene units could suppress regeneration between the injected electron and the oxidized dye effectively.

  • 2642.
    Zhao, Tony
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of functionalized allylic, propargylic and allenylic compounds: Selective formation of C–B, C–C, C–CF3 and C-Si bonds2015Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is focused on the development of new palladium and copper- mediated reactions for functionalization of alkenes and propargylic alcohol derivatives. The synthetic utility of the 1,2-diborylated butadienes synthesized in one of these processes has also been demonstrated.

    We have developed an efficient procedure for the synthesis of allenyl boronates from propargylic carbonates and acetates. This was achieved by using a bimetallic system of palladium and copper or silver as co-catalyst. The reactions were performed under mild conditions for the synthesis of a variety of allenyl boronates. Furthermore, the synthesis of 1,2-diborylated butadienes was achieved with high diastereoselectivity from propargylic epoxides. The reactivity of the 1,2-diborylated butadienes with aldehydes was studied. It was found that the initial allylboration reaction proceeds via an allenylboronate intermediate. The allenylboronate reacts readily with an additional aldehyde to construct 2-ethynylbutane-1,4-diols with moderate to high diastereoselectivity.

    We have also studied the copper-mediated trifluoromethylation of propargylic halides and trifluoroacetates. It was also shown that a transfer of chirality occurred when an enantioenriched starting material was used.

    In the last part of the thesis, we have described a method for palladium-catalyzed functionalization of allylic C-H bonds for the selective synthesis of allylic silanes. The protocol only works under highly oxidative conditions which suggest a mechanism involving high oxidation state palladium intermediates.

  • 2643.
    Zhao, Tony S. N.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Copper and Palladium-Mediated Transformationsof Allylic and Propargylic Substrates2014Licentiate thesis, monograph (Other academic)
    Abstract [en]

    This thesis is focused on the development of new palladium and copper-mediated reactions for functionalization of alkenes and propargylic alcohol derivatives. We have developed an efficient procedure for the synthesis of allenyl and propargyl boronate from propargylic carbonates and acetates. The reactions were performed under mild conditions for the synthesis of a variety of allenyl boronates. We have also observed a switch of regioselectivity for the formation of propargylic boronates using CuCl as a co-catalyst. This is, as far as we know, the first metal-catalyzed reaction for the synthesis of propargylic boronates. Furthermore, the synthesis of 1,2-diborylated butadienes was achieved with high diastereoselectivity from propargylic epoxides. A wide variety of propargylic epoxides could be converted to the corresponding dienes and this is the first catalytic protocol to form 1,2-diborylated butadienes.

    We have also studied the copper-mediated trifluoromethylation of propargylic halides and trifluoroacetates. Depending on the temperature, two different regioselective outcomes were observed. It was also shown that a transfer of chirality occurred when an enantioenriched starting material was used.

    In the last part of the thesis, we have described a method for palladium-catalyzed functionalization of allylic C-H bonds for selective synthesis of allylic silanes. The reaction is regioselective and gives only the linear allylic silane. The protocol only works under highly oxidative conditions which suggest a mechanism involving high oxidation state palladium intermediates.

  • 2644.
    Zhao, Tony S. N.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Trifluoromethylation of Propargylic Halides and Trifluoroacetates Using (Ph3P)(3)Cu(CF3) Reagent2012In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 14, no 15, p. 3966-3969Article in journal (Refereed)
    Abstract [en]

    A copper-mediated trifluoromethylation of propargylic halides and trifluoroacetates was performed with high allenyl or propargyl selectivity. The reaction proceeds smoothly with aliphatic and aromatic substituents bearing either electron-withdrawing or -supplying groups. Preliminary mechanistic results indicate an ionic mechanism involving nucleophilic transfer of the CF3 group from the Cu complex to the propargylic substrate.

  • 2645.
    Zhao, Tony S. N.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Yang, Yuzhu
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lessing, Timo
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Borylation of Propargylic Substrates by Bimetallic Catalysis. Synthesis of Allenyl, Propargylic, and Butadienyl Bpin Derivatives2014In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 136, no 21, p. 7563-7566Article in journal (Refereed)
    Abstract [en]

    Bimetallic Pd/Cu and Pd/Ag catalytic systems were used for borylation of propargylic alcohol derivatives. The substrate scope includes even terminal alkynes. The reactions proceed stererospecifically with formal S(N)2' pathways to give allenyl boronates. Opening of propargyl epoxides leads to 1,2-diborylated butadienes probably via en allenylboronate intermediate.

  • 2646. Zhou, Haitao
    et al.
    Huang, Wei
    Ding, Li
    Cai, Shengyun
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Li, Bo
    Su, Jianhua
    New cyano-substituted organic dyes containing different electrophilic groups: aggregation-induced emission and large two-photon absorption cross section2014In: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 70, no 39, p. 7050-7056Article in journal (Refereed)
    Abstract [en]

    Three aggregation-induced emission active dyes (3a-c) were synthesized and their one- and two-photon absorption properties have been investigated. They were all found to be weakly fluorescent in THF solution, while they exhibited dramatic fluorescence enhancement in water/THF mixtures. The solid fluorescence of 3a-c was recorded and their fluorescence quantum efficiency (Phi(F)) values were determined to be 8.0%, 8.1%, and 16.4%, respectively. Moreover, the two-photon absorption (2PA) cross-sections (sigma) of 3a-c were measured and 3a showed the highest value of 702 GM. The excellent aggregation-induced emission and 2PA properties provide a promising alternative for biophotonic materials.

  • 2647.
    Zhou, Hui
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Tunable cross coupling of silanols: Selective synthesis of heavily substituted allenes and butadienes2012In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 134, no 38, p. 15992-15999Article in journal (Refereed)
    Abstract [en]

    1,3-Dienyl-2-silanols with a wide range of substitution patterns are readily obtained by palladium-catalyzed silaboration of 1,3-enynes followed by Suzuki-Miyaura cross coupling with aryl bromides. Subsequent Hiyama-Denmark cross coupling with aryl iodides provides either 1,3- or 1,2-dienes in high yields. The site selectivity can be fully controlled by the choice of activator used in the coupling reaction. In the presence of strong bases such as NaOt-Bu, KOt-Bu, and NaH, clean formation of 1,2-dienes takes place via allylic rearrangement. In contrast, stereo- and site-selective formation of tetra- and trisubstituted 1,3-dienes results from use of Ag 2O and Bu 4NF·3H 2O, respectively, as activators. Under microwave heating at 100 °C the base-mediated cross couplings are largely accelerated and are completed within one hour or less. The ratio of diastereomeric allenes varies depending on the substitution pattern of the silanol and ranges from &gt;99:1 to 52:48.

  • 2648.
    Zhou, Juan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Butchosa, Núria
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Jayawardena, H. Surangi N.
    University of Massachusetts, United States .
    Park, JaeHyeung
    University of Massachusetts, United States .
    Zhou, Qi
    KTH, School of Chemical Science and Engineering (CHE), Centres, Wallenberg Wood Science Center. KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Yan, Mingdi
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. University of Massachusetts, United States .
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Synthesis of Multifunctional Cellulose Nanocrystals for Lectin Recognition and Bacterial Imaging2015In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 16, no 4, p. 1426-1432Article in journal (Refereed)
    Abstract [en]

    Multifunctional cellulose nanocrystals have been synthesized and applied as a new type of glyconanomaterial in lectin binding and bacterial imaging. The cellulose nanocrystals were prepared by TEMPO-mediated oxidation and acidic hydrolysis, followed by functionalization with a quinolone fluorophore and carbohydrate ligands. The cellulose nanocrystals were subsequently applied in interaction studies with carbohydrate-binding proteins and in bacterial imaging. The results show that the functional cellulose nanocrystals could selectively recognize the corresponding cognate lectins. In addition, mannosylated nanocrystals were shown to selectively interact with FimH-presenting E. coli, as detected by TEM and confocal fluorescence microscopy. These glyconanomaterials provide a new application of cellulose nanocrystals in biorecognition and imaging.

  • 2649.
    Zhou, Juan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Jayawardana, Kalana
    University of Massachusetts, United States .
    Kong, Na
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ren, Yansong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Hao, Nanjing
    Yan, Mingdi
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry. University of Massachusetts, United States .
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Trehalose-Conjugated Mesoporous Silica Nanoparticles for Efficient Delivery of Isoniazid into MycobacteriaManuscript (preprint) (Other academic)
  • 2650.
    Zhou, Taigang
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Synthetical Organic Chemistry.
    Asymmetric Hydrogenation of Functionalized Olefins Using N,P-Ligated Iridium Complexes2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Transition-metal-catalyzed asymmetric hydrogenation is one of the most efficient, straightforward, and well-established methods for preparing enantiomerically enriched compounds. Over the past decades, significant progress has been made with iridium, rhodium and ruthenium complexes to asymmetric hydrogenate a selection of olefins, such as, α,β-unsaturated carboxylic acid derivatives, ketones, imines and phosphonates. Although these metals have been applied successfully in the hydrogenation of olefins, they differ in their substrate tolerance.  Ruthenium and rhodium based catalysts require a coordinating group in the vicinity of the C=C bond. However, iridium based catalysts do not require this coordinating group, hence, asymmetric hydrogenation with iridium catalysts has been widely used for both functionalized and unfunctionalized olefin substrates. This thesis focuses on expanding the substrate scope for asymmetric hydrogenation using chiral N,P-ligated iridium catalysts. Papers I and II investigate the asymmetric hydrogenation of prochiral N-heterocyclic compounds prepared by ring-closing metathesis using the iridium catalysts developed in our group.  These substrates are interesting as they bear resemblance to pharmaceutically active compounds and therefore have tremendous value in medicinal chemistry.  Excellent enantioselectivities, up to >99% ee and conversions were obtained. In papers III and IV we synthesized many unsaturated acyclic and cyclic sulfones with varying substitution patterns.  The sulfones were subjected to hydrogenation using our N,P-ligated iridium catalysts, producing the chiral sulfone products in high enantiomeric excess (up to 99% ee). This methodology was combined with the Ramberg-Bäcklund reaction, offering a novel route to chiral allylic and homoallylic compounds. In addition to obtaining these chiral compounds in good yields, no decrease in enantiomeric excess was observed after the Ramberg-Bäcklund reaction. This strategy has been applied in the preparation of the chiral building block for renin inhibitors.

5051525354 2601 - 2650 of 2694
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