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  • 1. Belda, O.
    et al.
    Lundgren, S.
    Moberg, Christina
    KTH, Superseded Departments, Chemistry.
    Recoverable resin-supported pyridylamide ligand for microwave-accelerated molybdenum-catalyzed asymmetric allylic alkylations: Synthesis of baclofen2003In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 5, no 13, p. 2275-2278Article in journal (Refereed)
    Abstract [en]

    The syntheses of a series of 4-monosubstituted pyridylamides and a resin-supported pyridylamide are described. The ligands were evaluated in the microwave-accelerated molybdenum-catalyzed asymmetric allylic alkylation. The reaction afforded the product in high yield and with high regio- and enantioselectivity. The heterogeneous ligand could be reused several times with no change in the reaction outcome. The asymmetric allylic alkylation was employed as the key step in the enantioselective synthesis of (R)-baclofen.

  • 2.
    Frölander, Anders
    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.
    Ag+-Assisted Hydrosilylation: Complementary Behavior of Rh and Ir Catalysts (Reversal of Enantioselectivity)2007In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 9, no 7, p. 1371-1374Article in journal (Refereed)
    Abstract [en]

    The presence of a suitably situated hydroxy function in a PHOX ligand leads to an enhancement of the enantioselectivity in Rh-catalyzed hydrosilylations of prochiral ketones in the presence of AgBF4 (95% ee for acetophenone as compared to 75% using i-Pr-phosphinooxazoline (PHOX)). Exchanging Rh for Ir affords the product with the opposite absolute configuration (78% ee).

  • 3.
    Gerdin, Martin
    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.
    Ni-Catalyzed Si-B Addition to 1,3-Dienes: Disproportionation in Lieu of Silaboration2006In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 8, no 14, p. 2929-2932Article in journal (Refereed)
    Abstract [en]

    Upon attempted silaboration of acyclic 1- and 1,4-substituted 1,3-dienes, a new disproportionation reaction was discovered, yielding 1:1 mixtures of allylsilanes and dienylboranes. It was demonstrated that, as a key step in this new catalytic process, hydrogen is being transferred from one diene moiety to another.

  • 4. Holmquist, M.
    et al.
    Berglund, Per
    KTH, School of Biotechnology (BIO), Biochemistry (closed 20130101).
    Creation of a synthetically useful lipase with higher than wild-type enantioselectivity and maintained catalytic activity1999In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 1, no 5, p. 763-765Article in journal (Refereed)
    Abstract [en]

    Formula presented Wild type I: 89.9% ee (E=32) Wild type II: 79.8% ee (E=10) Lipase hybrid: 95.4% ee (E=54) We have found that two Geotrichum candidum lipase isozymes have remarkably different abilities to differentiate between enantiomers of ethyl 2-methyldecanoate. By rational recombination of selected portions of the two isozymes, we have created a novel lipase with an enantioselectivity superior to that of the best wild-type parent isozyme. Site-directed mutagenesis identified two key amino acid residues responsible for the improved enantioselectivity without compromised total activity of the reengineered enzyme.

  • 5.
    Hsieh, Yves S. Y.
    et al.
    University of Sydney, Australia.
    Wilkinson, Brendan L.
    O'Connell, Mitchell R.
    Mackay, Joel P.
    Matthews, Jacqueline M.
    Payne, Richard J
    Synthesis of the bacteriocin glycopeptide sublancin 168 and S-glycosylated variants2012In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 14, no 7, p. 1910-3Article in journal (Refereed)
    Abstract [en]

    The synthesis of sublancin 168, a unique S-glucosylated bacteriocin antibiotic, is described. The natural product and two S-glycosylated variants were successfully prepared via native chemical ligation followed by folding. The synthetic glycopeptides were shown to possess primarily an α-helical secondary structure by CD and NMR studies.

  • 6. Kong, Jiahui
    et al.
    Zhang, Qiong
    Savage, Mathew
    Li, Minzhi
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Yang, Sihai
    Liang, Xu
    Zhu, Weihua
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Xie, Yongshu
    Tetra- and Octapyrroles Synthesized from Confusion and Fusion Approaches2016In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 18, no 19, p. 5046-5049Article in journal (Refereed)
    Abstract [en]

    By oxidation of an alternately N-confused bilane in CH2Cl2, a C-N fused tetrapyrrin was synthesized that bears a 5.5.5-tricyclic ring generated from an intramolecular C-N linkage. When CH3CN was used as the reaction medium, a multiply C-N-fused octapyrrolic dimer was also obtained that contained two 5.5.5.7.5-pentacyclic moieties and a bipyrrole unit generated from the intramolecular C-N linkage and intermolecular C-C linkage, respectively. This could be coordinated with Ni(acac)(2) to afford a mixed-ligand complex.

  • 7. Kumar, Sangit
    et al.
    Johansson, Henrik
    Kanda, Takahiro
    Engman, Lars
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Müller, Thomas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Jonsson, Mats
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Nuclear Chemistry.
    Pedulli, Franco
    Petrucci, Silvia
    Valgimigli, Luca
    Catalytic Chain-Breaking Pyridinol Antioxidants2008In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 10, no 21, p. 4895-4898Article in journal (Refereed)
    Abstract [en]

    When assayed for their capacity to inhibit azo-initiated peroxidation of linoleic acid in a water/chlorobenzene two-phase system, tellurium-containing 3-pyridinols were readily regenerable by N-acetylcysteine contained in the aqueous phase. The best inhibitors quenched peroxyl radicals more efficiently than alpha-tocopherol, and the duration of inhibition was limited only by the availability of the thiol reducing agent. The compounds were also found to catalyze reduction of hydrogen peroxide in the presence of thiol reducing agent.

  • 8.
    Kärkäs, Markus D.
    et al.
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Organic chemistry. Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States.
    Bosque, Irene
    Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States.
    Matsuura, Bryan S.
    Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States.
    Stephenson, Corey R. J.
    Department of Chemistry, University of Michigan, Ann Arbor, Michigan 48109, United States.
    Photocatalytic Oxidation of Lignin Model Systems by Merging Visible-Light Photoredox and Palladium Catalysis2016In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 18, no 19, p. 5166-5169Article in journal (Refereed)
    Abstract [en]

    Lignin valorization has long been recognized as a sustainable solution for the renewable production of aromatic compounds. Two-step oxidation/reduction strategies, whereby the first oxidation step is required to “activate” lignin systems for controlled fragmentation reactions, have recently emerged as viable routes toward this goal. Herein we describe a catalytic protocol for oxidation of lignin model systems by combining photoredox and Pd catalysis. The developed dual catalytic protocol allowed the efficient oxidation of lignin model substrates at room temperature to afford the oxidized products in good to excellent yields.

  • 9. Li, Hong
    et al.
    Li, Xin
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Ågren, Hans
    KTH, School of Biotechnology (BIO), Theoretical Chemistry and Biology.
    Qu, Da-Hui
    Two Switchable Star-Shaped [1](n)Rotaxanes with Different Multibranched Cores2014In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 16, no 18, p. 4940-4943Article in journal (Refereed)
    Abstract [en]

    Two novel star-shaped [1](n)rotaxanes with three and four identical [1]rotaxane arms but different multibranched cores were designed, synthesized, and well-characterized. In the two systems, external base acid stimuli result in the uniform relative mechanical movement of the macrocydic rings and threads of their [1]rotaxane arms. The energy-minimized structures of the two rotaxanes in different states were obtained using molecular dynamics simulations in acetone solution, suggesting the construction of more sophisticated molecular machines mimicking the extension and contraction motions.

  • 10.
    Linder, Mats
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Johansson, Adam Johannes
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Brinck, Tore
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Physical Chemistry.
    Mechanistic Insights into the Stepwise Diels-Alder Reaction of 4,6-Dinitrobenzofuroxan2012In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 14, no 1, p. 118-121Article in journal (Refereed)
    Abstract [en]

    The stepwise Diels-Alder reaction between 1-trimethylsiloxy-1,3-butadiene and 4,6-dinitrobenzofuroxan is explored using state-of-the-art computational methods. The results support a stepwise mechanism via a persistent Intermediate, however, not the one previously reported (Lakhdar et al., Chem. Eur. J. 2007, 16,5681) but a heterocyclic adduct. The novel OFT functional M062X and the SCS-MP2 method were essential to reproduce a reasonable potential energy surface for this challenging system.

  • 11. Luken, Christian
    et al.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Silaborations of 1,3-enynes - Substrate controlled allene/1,3-diene selectively2008In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 10, no 12, p. 2505-2508Article in journal (Refereed)
    Abstract [en]

    Silaboration of 1,3-enynes catalyzed by group 10 metal complexes affords 1,3-dienes with vinylborane and vinylsilane functions or 1,2-dienes with allylborane and vinylsilane functions. The type of product formed is determined by the size of the alkyne substituent.

  • 12.
    Lundgren, Stina
    et al.
    KTH, Superseded Departments, Chemistry.
    Lutsenko, S.
    KTH, Superseded Departments, Chemistry.
    Jönsson, C.
    KTH, Superseded Departments, Chemistry.
    Moberg, Christina
    KTH, Superseded Departments, Chemistry.
    Polymer-Supported Pyridine-Bis(oxazoline). Application to Ytterbium Catalyzed Silylcyanation of Benzaldehyde2003In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 5, no 20, p. 3663-3665Article in journal (Refereed)
    Abstract [en]

    Terminal acetylenes containing hydroxy and carboxylic acid groups were subjected to Sonogashira coupling with 4-bromo-2,6-bis[(R)-4-phenyloxazolin-2-yl]pyridine and the resulting pybox derivatives were immobilized on Tentagel resins. Ytterbium(ill) chloride complexes of the polymeric ligands catalyzed the addition of trimethylsilyl cyanide to benzaldehyde with 80-81% ee. The ligands were reused more than 30 times without any loss in selectivity or activity, and the metal complexes could be recovered and reused at least four times, although with slightly decreasing activity.

  • 13. Olofsson, B.
    et al.
    Khamrai, U.
    Somfai, Peter
    KTH, Superseded Departments, Chemistry.
    A regio- and stereodivergent synthesis of vic-amino alcohols2000In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 2, no 25, p. 4087-4089Article in journal (Refereed)
    Abstract [en]

    [GRAPHICS] A regio- and stereodivergent synthesis of vic-amino alcohols starting from vinylepoxides is described. The developed strategy focuses on the propensity of vinylepoxides and vinylaziridines to be ring-opened at the allylic position by suitable nucleophiles and makes use of reactions that perform such tasks selectively with either retention or inversion of configuration.

  • 14.
    Prathap, Kaniraj Jeya
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Wu, Qiong
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Olsson, Richard T.
    KTH, School of Chemical Science and Engineering (CHE), Fibre and Polymer Technology.
    Dinér, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Catalytic Reductions and Tandem Reactions of Nitro Compounds Using in Situ Prepared Nickel Boride Catalyst in Nanocellulose Solution2017In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 19, no 18, p. 4746-4749Article in journal (Refereed)
    Abstract [en]

    A mild and efficient method for the in situ reduction of a wide range of nitroarenes and aliphatic nitrocompounds to amines in excellent yields using nickel chloride/sodium borohydride in a solution of TEMPO-oxidized nanocellulose in water (0.01 wt %) is described. The nanocellulose has a stabilizing effect on the catalyst, which increases the turnover number and enables low loading of nickel catalyst (0.1-0.25 mol % NiCl2). In addition, two tandem protocols were developed in which the in situ formed amines were either Boc-protected to carbamates or further reacted with an epoxide to yield β-amino alcohols in excellent yields.

  • 15.
    Qian, Zhengliang
    et al.
    East China Univ Sci & Technol, Sch Chem & Mol Engn, Feringa Nobel Prize Scientist Joint Res Ctr, Key Lab Adv Mat, 130 Meilong Rd, Shanghai 200237, Peoples R China.;East China Univ Sci & Technol, Sch Chem & Mol Engn, Feringa Nobel Prize Scientist Joint Res Ctr, Joint Int Res Lab Precis Chem & Mol Engn, 130 Meilong Rd, Shanghai 200237, Peoples R China..
    Li, Xin
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Yuan, Tao
    East China Univ Sci & Technol, Sch Chem & Mol Engn, Feringa Nobel Prize Scientist Joint Res Ctr, Key Lab Adv Mat, 130 Meilong Rd, Shanghai 200237, Peoples R China.;East China Univ Sci & Technol, Sch Chem & Mol Engn, Feringa Nobel Prize Scientist Joint Res Ctr, Joint Int Res Lab Precis Chem & Mol Engn, 130 Meilong Rd, Shanghai 200237, Peoples R China..
    Huang, Xinghua
    East China Univ Sci & Technol, Sch Chem & Mol Engn, Feringa Nobel Prize Scientist Joint Res Ctr, Key Lab Adv Mat, 130 Meilong Rd, Shanghai 200237, Peoples R China.;East China Univ Sci & Technol, Sch Chem & Mol Engn, Feringa Nobel Prize Scientist Joint Res Ctr, Joint Int Res Lab Precis Chem & Mol Engn, 130 Meilong Rd, Shanghai 200237, Peoples R China..
    Wang, Qiaochun
    East China Univ Sci & Technol, Sch Chem & Mol Engn, Feringa Nobel Prize Scientist Joint Res Ctr, Key Lab Adv Mat, 130 Meilong Rd, Shanghai 200237, Peoples R China.;East China Univ Sci & Technol, Sch Chem & Mol Engn, Feringa Nobel Prize Scientist Joint Res Ctr, Joint Int Res Lab Precis Chem & Mol Engn, 130 Meilong Rd, Shanghai 200237, Peoples R China..
    Agren, Hans
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Theoretical Chemistry and Biology.
    Tian, He
    East China Univ Sci & Technol, Sch Chem & Mol Engn, Feringa Nobel Prize Scientist Joint Res Ctr, Key Lab Adv Mat, 130 Meilong Rd, Shanghai 200237, Peoples R China.;East China Univ Sci & Technol, Sch Chem & Mol Engn, Feringa Nobel Prize Scientist Joint Res Ctr, Joint Int Res Lab Precis Chem & Mol Engn, 130 Meilong Rd, Shanghai 200237, Peoples R China..
    Divalent Pseudorotaxane with Polarized Plug-Socket and Padlock Functions2018In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 20, no 6, p. 1487-1490Article in journal (Refereed)
    Abstract [en]

    A dual-pore structured host composed of one 24-crown-8 and one 34-crown-10, and a "U"-shaped guest consisting of two different recognition units, one dibenzylammonium and one viologen, were synthesized and bound 1:1 into a divalent pseudorotaxane P1. P1 can mimic the inserting and pulling out functions of a polarized plug-socket system under solvent driven stimulus and can also realize the locking and unlocking actions of a padlock under pH stimulus.

  • 16.
    Restorp, Per
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Somfai, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Diastereoselective Aldol Additions to α-Amino-β-Silyloxy Aldehydes. Divergent Synthesis of Aminodiols2005In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 7, no 5, p. 893-895Article in journal (Refereed)
    Abstract [en]

    A divergent protocol for substrate-controlled diastereoselective synthesis of aminodiols has been developed using nucleophilic Mukaiyama aldol additions to alpha-amino-beta-silyloxy aldehydes. The merged stereochemical impact on the diastereoselectivity of the polar alpha- and beta-substituents is highlighted.

  • 17. Rotticci, D.
    et al.
    Norin, T.
    Hult, Karl
    KTH, Superseded Departments, Biochemistry and Biotechnology.
    Mass transport limitations reduce the effective stereospecificity in enzyme-catalyzed kinetic resolution2000In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 2, no 10, p. 1373-1376Article in journal (Refereed)
    Abstract [en]

    The kinetic resolution of seudenol catalyzed by Candida antarctica lipase a in hexane was investigated. Large differences in reaction rate and stereospecificity were observed when different enzyme preparations were used, These differences were ascribed to mass transport limitations which reduced both reaction rate and stereospecificity. Lyophilized enzyme preparations were more apt to give this problem than immobilized preparations. Further, low substrate concentrations enhanced the effect. Thus, high alcohol concentrations and enzyme immobilization can be recommended.

  • 18.
    Seashore-Ludlow, Brinton
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Saint-Dizier, Francois
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Somfai, Peter
    Asymmetric Transfer Hydrogenation Coupled with Dynamic Kinetic Resolution in Water: Synthesis of anti-beta-Hydroxy-alpha-amino Acid Derivatives2012In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 14, no 24, p. 6334-6337Article in journal (Refereed)
    Abstract [en]

    The use of asymmetric transfer hydrogenation combined with dynamic kinetic resolution for the synthesis of beta-hydroxy-alpha-(tert-butoxycarbonyl)-amino esters in water is described. This procedure provides the desired amino alcohols in good yields, diastereoselectivities, and enantioselectivities. A surfactant is employed to achieve good yields due to the hydrophobic nature of both the catalyst and substrate. The reaction setup is operationally simple, and nondegassed water can be used as the solvent.

  • 19.
    Seashore-Ludlow, Brinton
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Somfai, Peter
    Domino Carbopalladation-Carbonylation: Generating Quaternary Stereocenters while Controlling beta-Hydride Elimination2010In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 12, no 17, p. 3732-3735Article in journal (Refereed)
    Abstract [en]

    A domino carbopalladation-carbonylation sequence for substrates possessing beta-hydrogens is explored. This allows for the construction of complex architectures with vicinal stereocenters in a concise and rapid fashion via the stereocontrolled formation of two carbon carbon bonds. An integral aspect of this domino reaction is the ability to control beta-hydride elimination of the organopalladium intermediate and instead form the carbonylation product.

  • 20.
    Seashore-Ludlow, Brinton
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Somfai, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Domino carbopalladation-cross-coupling for the synthesis of 3,3-disubstituted oxindoles2012In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 14, no 15, p. 3858-3861Article in journal (Refereed)
    Abstract [en]

    This study examines a domino carbopalladation-cross-coupling reaction for the formation of valuable oxindole scaffolds. Furthermore, the reaction sequence forges vicinal stereocenters in a stereospecific manner through the formation of two carbon-carbon bonds and, thereby, rapidly generates complexity. The reaction gives high yields for a variety of acrylamide substrates, and various organoboranes have also been evaluated for the cross-coupling. This work offers insight into the relative rates determining a successful carbopalladation-cross- coupling reaction and how to favor the desired reaction pathway.

  • 21.
    Seashore-Ludlow, Brinton
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Villo, Piret
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Häcker, Christine
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Somfai, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Enantioselective Synthesis of anti-beta-Hydroxy-alpha-amido Esters via Transfer Hydrogenation2010In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 12, no 22, p. 5274-5277Article in journal (Refereed)
    Abstract [en]

    The asymmetric transfer hydrogenation of alpha-amido-beta-keto esters to provide the corresponding anti-beta-hydroxy-alpha-amido esters in good to excellent yields, diastereoselectivity, and enantioselectivity is reported. The procedure is operationally simple, and delicate handling of the catalyst is not necessary.

  • 22.
    Strand, Daniel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Rein, Tobias
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Synthesis of Pyragonicin2005In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 7, no 13, p. 2779-2781Article in journal (Refereed)
    Abstract [en]

    A stereocontrolled convergent synthesis of the annonaceous acetogenin pyragonicin (1) is presented. The key intermediates were accessed using asymmetric Horner-Wadsworth-Emmons (HWE) methodology. A reagent controlled zinc-mediated stereoselective coupling, joining the two highly functionalized intermediates 3 and 4, then provided the core structure.

  • 23.
    Strand, Daniel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Rein, Tobias
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Total Synthesis of Pyranicin2005In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 7, no 2, p. 199-202Article in journal (Refereed)
    Abstract [en]

    A stereocontrolled convergent synthesis of the annonaceous acetogenin pyranicin (1) is presented. Asymmetric Horner-Wadsworth-Emmons (HWE) reactions were used to access key intermediates. The tetrahydropyran derivative 2 was obtained via an asymmetric desymmetrization of the meso-dialdehyde 6, and the butenolide fragment was constructed using a stereoconvergent reaction sequence involving a parallel kinetic HWE resolution followed by a Pd-catalyzed allylic substitution. The C10/C15 1,6-diol motif was installed using Carreira's asymmetric acetylide addition methodology.

  • 24. Stranne, R.
    et al.
    Vasse, J. L.
    Moberg, Christina
    KTH, Superseded Departments, Chemistry.
    Synthesis and application of chiral P,N-ligands with pseudo-meso and pseudo-C-2 symmetry2001In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 3, no 16, p. 2525-2528Article in journal (Refereed)
    Abstract [en]

    [GRAPHICS] Two diastereoisomeric P,N-ligands, (S,S)-1 and (R,S)-1, were synthesized and assessed in palladium-catalyzed allylic alkylations. With rac-1,3-diphenylpropenyl acetate as substrate, ligand (AS)-1, with pseudo-C-2 symmetry, exhibited higher reactivity and higher enantioselectivity than the pseudo-meso ligand (R,S)-1, whereas reversal reactivity and selectivity were observed with rac-3-cyclohexenyl acetate.

  • 25. Teng, Chao
    et al.
    Yang, Xichuan
    Yuan, Chunze
    Li, Chaoyan
    Chen, Ruikui
    Tian, Haining
    Li, Shifeng
    Hagfeldt, Anders
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Sun, Licheng
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Two Novel Carbazole Dyes for Dye-Sensitized Solar Cells with Open-Circuit Voltages up to 1 V Based on Br-/Br-3(-) Electrolytes2009In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 11, no 23, p. 5542-5545Article in journal (Refereed)
    Abstract [en]

    Dye-sensitized solar cells (DSCs) based on two novel carbazole dyes (TC301 and TC306) and a Br-/Br-3(-) redox mediator in dried CH3CN solutions as electrolytes yielded a V-oc of 1.156 V and a eta value of 3.68% and a V-oc of 0.939 V and a eta value of 5.22% under simulated AM 1.5, respectively. The dyes TC301 and TC306 have more positive HOMO levels (1.59 and 1.38 V vs NHE) than the redox potential of Br-/Br-3(-)-based electrolytes, which have sufficient driving force to regenerate dyes. Under similar conditions with an I-/I-3(-) instead of a Br-/Br-3(-) redox mediator, DSCs sensitized by the dyes TC301 and TC306 produced a V-oc of 0.696 V and a eta value of 2.36% and a V-oc of 0.621 V and a eta value of 4.10%, respectively.

  • 26. Thomas, Gemma L.
    et al.
    Hsieh, Yves S. Y.
    University of Sydney, Australia.
    Chun, Candy K. Y.
    Cai, Zheng-Li
    Reimers, Jeffrey R.
    Payne, Richard J.
    Peptide ligations accelerated by N-terminal aspartate and glutamate residues.2011In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 13, no 18, p. 4770-3Article in journal (Refereed)
    Abstract [en]

    A novel application of intramolecular base catalysis confers enhanced reaction rates for aminolysis ligations between peptide thioesters and peptides bearing N-terminal aspartate or glutamate residues. The broad scope of this process and its application in the total synthesis of the diabetes drug exenatide is demonstrated.

  • 27.
    Tuzina, Pavel
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Somfai, Peter
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Asymmetric Lewis Acid Mediated 1,2 -Rearrangement of Proline-Derived Ammonium Ylides2009In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 11, no 4, p. 919-921Article in journal (Refereed)
    Abstract [en]

    The first example of asymmetric Lewis acid mediated [1,2]-rearrangement of N-benzylic proline amides to form quaternary proline derivatives is reported. The presented reaction is shown to proceed with remarkable high C-N-C chirality transfer. Various quaternary proline derivatives have been prepared in good to excellent yields and high enantiomeric purity.

  • 28.
    Xiao, You-Cai
    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.
    Silaborative Carbocyclizations of 1,7-Enynes. Diastereoselective Preparation of Chromane Derivatives2016In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 18, no 2, p. 308-311Article in journal (Refereed)
    Abstract [en]

    Palladium(0)-catalyzed carbocyclization of 1,7-enynes mediated by (chlorodimethylsilyl)pinacolborane proceeds with 1,8-addition of the silicon and boron functions to give functionalized cyclohexane derivatives with boron attached to the exocyclic olefin. A variety of chromane dervatives are accessible by this method. In contrast to the analogous reactions with 1,6-enynes, the configuration of the newly formed stereogenic center is controlled by a stereogenic center present in the substrate.

  • 29.
    Xie, Sheng
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Yan, Mingdi
    KTH, School of Chemical Science and Engineering (CHE), Chemistry. University of Massachusetts Lowell, United States.
    N,N-Diethylurea-Catalyzed Amidation between Electron-Deficient Aryl Azides and Phenylacetaldehydes2015In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 17, no 3, p. 636-639Article in journal (Refereed)
    Abstract [en]

    Urea structures, of which N,N-diethylurea (DEU) proved to be the most efficient, were discovered to catalyze amidation reactions between electron-deficient aryl azides and phenylacetaldehydes. Experimental data support 1,3-dipolar cycloaddition between DEU-activated enols and electrophilic phenyl azides, especially perfluoroaryl azides, followed by rearrangement of the triazoline intermediate. The activation of the aldehyde under near-neutral conditions was of special importance in inhibiting dehydration/aromatization of the triazoline intermediate, thus promoting the rearrangement to form aryl amides.

  • 30. 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.

  • 31. 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.

  • 32.
    Zhou, Hui
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry.
    Moberg, Christina
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Regio- and Stereoselective Hydrosilylation of 1,3-Enynes Catalyzed by Palladium2013In: Organic Letters, ISSN 1523-7060, E-ISSN 1523-7052, Vol. 15, no 7, p. 1444-1447Article in journal (Refereed)
    Abstract [en]

    In the presence of Pd(0) and a phosphine, hydrosilylation of 1,3-enynes with Me2SiHCI proceeds to yield dienylsilanes with the silicon function added to the internal alkyne carbon atom and with (E)-configuration of newly formed olefinic bond. The silanols isolated after hydrolysis of the primarily obtained products serve as precursors to conjugated dienes with different substitution patterns.

1 - 32 of 32
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