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  • 1.
    Ahlford, Katrin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Livendahl, Madeleine
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Fine-tuning catalytic activity and selectivity-[Rh(amino acid thioamide)] complexes for efficient ketone reduction2009In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 50, no 46, p. 6321-6324Article in journal (Refereed)
    Abstract [en]

    Amino acid-derived thioamides are prepared and evaluated as ligands in the rhodium-catalyzed asymmetric transfer hydrogenation of ketones in 2-propanol. It is found that increasing the steric bulk at the C-terminus of the ligand had a positive impact on both activity and selectivity in the reduction reaction. In order to find the optimum catalyst, a study is performed on a series of thioamide ligands having substituents of varying size.

  • 2. Ahmad, Anees
    et al.
    Scarassati, Paulo
    Jalalian, Nazli
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Universidade de São Paulo, Brazil.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Silva, Luiz F., Jr.
    Oxidative rearrangement of alkenes using in situ generated hypervalent iodine(III)2013In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 54, no 43, p. 5818-5820Article in journal (Refereed)
    Abstract [en]

    A novel protocol for the oxidative rearrangement of alkenes using in situ generated hypervalent iodine(III) was developed. This approach uses inexpensive, readily available, and stable chemicals (PhI, mCPBA, and TsOH) giving rearrangement products in yields comparable to those obtained using the more expensive commercially available [hydroxy(tosyloxy)iodo]benzene [HTIB or Koser's reagent]. Additionally, an alternative protocol for the synthesis of 1-methyl-2-tetralone through the one-step epoxidation/rearrangement of 4-methyl-1,2-dihydronaphthalene using mCPBA and TsOH was developed.

  • 3.
    Aydin, Juhanes
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Selander, Nicklas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Strategies for fine-tuning the catalytic activity of pincer-complexes2006In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 47, no 50, p. 8999-9001Article in journal (Refereed)
    Abstract [en]

    Various methoxy substituted pincer-complexes were prepared in order to study the substituent effects on the catalytic activity in palladium catalyzed opening of vinyl epoxides and boronation of cinnamyl alcohol. The results clearly show that methoxy substitution at the para-position of the pincer-complex leads to up to fourfold acceleration of the catalytic reactions, while substitution of the side-arms does not change the activity of the complex or leads to a slight deceleration of the catalytic processes.

  • 4.
    Bogár, Krisztián
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    High-yielding metalloenzymatic dynamic kinetic resolution of fluorinated aryl alcohols2007In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 48, no 31, p. 5471-5474Article in journal (Refereed)
    Abstract [en]

    Dynamic kinetic resolution (DKR) of various fluorinated aryl alcohols by a combination of lipase-catalyzed enzymatic resolution with in situ ruthenium-catalyzed alcohol racemization is described. (R)-Selective Candida antarctica lipase B (CALB) was employed for transesterification of different fluoroaryl alcohols in DKR reactions delivering the corresponding acetates in high yield (97%) with excellent enantiomeric excess (98%).

  • 5.
    Borén, Linnéa
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Leijondahl, Karin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dynamic Kinetic Asymmetric Transformation of 1,4-diols and Preparation of Trans-2,5-Disubstituted pyrrolidines2009In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 50, no 26, p. 3237-3240Article in journal (Refereed)
    Abstract [en]

    Dynamic kinetic asymmetric transformation (DYKAT) of a series of 1,4-diols is carried out with Candida antarctica lipase B (CALB), Pseudomonas cepacia lipase II (PS-C II), and a ruthenium catalyst. A β-chloro-substituted 1,4-diol is successfully transformed into an optically pure 1,4-diacetate, which is a highly useful synthetic intermediate. The usefulness of the optically pure 1,4-diacetates is demonstrated by the synthesis of enantiopure 2,5-disubstituted pyrrolidines.

  • 6.
    Csjernyik, Gábor
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bogár, Krisztián
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    New Efficient Ruthenium Catalysts for Racemization of Alcohols at Room Temperature2004In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 45, no 36, p. 6799-6802Article in journal (Refereed)
    Abstract [en]

    5-Pentaphenylcyclopentadienyl)RuCl(CO)2 was found to catalyze efficiently the racemization of chiral alcohols such as (S)-1-phenylethanol, (S)-1-phenylpropan-2-ol, (S)-4-phenylbutan-2-ol and (S)-4-methoxy-1-phenylethanol at room temperature in the presence of a base. The catalytic activity of three other Ru(II) complexes was also investigated. The effects of halide and solvent were studied as well.

  • 7.
    Danielsson, Marie
    et al.
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    Wahlström, Karolina
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    Undén, Anders
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    Protection of the indole nucleus of tryptophan in solid-phase peptide synthesis with a dipeptide that can be cleaved rapidly at physiological pH2011In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 52, no 44, p. 5876-5879Article in journal (Refereed)
    Abstract [en]

    The synthesis of a new derivative of tryptophan Fmoc-Trp(Boc-Sar-Sar)-OH is described. Fmoc-Trp(Boc-Sar-Sar)-OH is introduced into peptides by solid-phase peptide synthesis and during treatment with TFA at the end of the synthesis, the Boc group is cleaved and the peptide is obtained with the indole nucleus modified with the sarcosinyl-sarcosinyl (Sar-Sar) moiety. This modification will introduce a cationic charge that improves the solubility of the peptide during HPLC purification. The Sar-Sar moiety is cleaved upon exposure to physiological pH. The Boc-Sar-Sar group might, therefore, also find use in the design of pro-drugs of indole-containing compounds.

  • 8.
    Deiana, Luca
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhao, Gui-Ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dziedzik, Pawel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Rios, Ramón
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Vesely, Jan
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ekström, Jesper
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    One-pot highly enantioselective catalytic Mannich-type reactions between aldehydes and stable α-amido sulfones: asymmetric synthesis of β-amino aldehydes and β-amino acids2010In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 51, no 2, p. 234-237Article in journal (Refereed)
    Abstract [en]

    A highly enantioselective catalytic route to carbamate- and benzoate-protected beta-amino aldehydes and beta-amino acids is presented. The amino acid-catalyzed one-pot asymmetric reaction between unmodified aldehydes and alpha-amido sulfones gives the corresponding beta-amino compounds with up to 95:5 dr and 97-99%

  • 9.
    Dziedzic, Pawel
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bartoszewicz, Agnieszka
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Inorganic ammonium salts as catalysts for direct aldol reactions in the presence of water2009In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 50, no 52, p. 7242-7245Article in journal (Refereed)
  • 10.
    Dziedzic, Pawel
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ibrahem, Ismail
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Direct catalytic asymmetric three-component Mannich reactions with dihydroxyacetone: enantioselective synthesis of amino sugar derivatives2008In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 49, no 5, p. 803-807Article in journal (Refereed)
    Abstract [en]

    Highly enantioselective, amino acid-catalyzed, one-pot three-component asymmetric Mannich reactions between dihydroxyacetone, p-anisidine, and aldehydes are presented. The reactions proceeded with high chemo- and stereoselectivity and furnished the corresponding α,α′-dihydroxy-β-aminoketones in high yields with 82–95% ee.

  • 11.
    Edin, Michaela
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E.
    Córdova, Armando
    Tandem enantioselective organo- and biocatalysis: a direct entry for the synthesis of enantiomerically pure aldols2004In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 45, p. 7697-7701Article in journal (Refereed)
  • 12.
    Eiríksdóttir, Emelía
    et al.
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    Langel, Ülo
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    Rosenthal-Aizman, Katri
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    An improved synthesis of releasable luciferin-CPP conjugates2009In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 50, no 33, p. 4731-4733Article in journal (Refereed)
    Abstract [en]

    We have improved the synthesis of a previously published luciferin-linker, used in an assay enabling rapid real-time quantification of luciferin–CPP conjugate uptake and cytosolic cargo release. We also present the synthesis of a new luciferin-linker with the same conjugation ability. Both luciferin-linkers are now available via an efficient one-pot procedure.

  • 13.
    Erlandsson, Mikael
    et al.
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    Undén, Anders
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    3-(4-hydroxymethylphenylsulfanyl)propanoic acid (HMPPA) as a new safety catch linker in solid phase peptide synthesis2006In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 32, no 7, p. 5829-5832Article in journal (Refereed)
    Abstract [en]

    A new safety catch linker, 3-(4-hydroxymethylphenylsulfanyl)propanoic acid (HMPPA), is described for use in solid phase peptide synthesis. The linker is readily synthesized from commercially available chemicals in a more cost efficient way compared to similar reported linkers. The HMPPA linker is easily attached to an amino derivatized solid support followed by on-resin oxidation of the thioether to sulfoxide, thereby making the linker very stable towards strong acid treatment. Final resin cleavage is performed by reductive acidolysis.

  • 14.
    Fournière, Viviane
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Cumpstey, Ian
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of non-glycosidically linked selenoether pseudodisaccharides2010In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 51, no 16, p. 2127-2129Article in journal (Refereed)
    Abstract [en]

    Non-glycosidically linked disaccharide mimetics with a selenoether functionality linking the two monosaccharide residues have been synthesised. Protected Glc(Se3–3)Glc, Glc(Se3–6)Glc and Glc(Se3–6)Man structures were obtained. Selenium was introduced by displacement of carbohydrate sulfonates with a selenobenzoate anion. Conversion into diselenides by methanolysis of the benzoate and aerial oxidation was followed by reduction of the diselenides to selenolates, and in situ displacement of a second carbohydrate sulfonate in an SN2 reaction to give selenoethers. Glc(Se3–3)Glc and Glc(Se3–6)Glc were also obtained in deprotected form.

  • 15.
    Frigell, Jens
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Cumpstey, Ian
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    First synthesis of 4a-carba-beta-D-galactofuranose2007In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 48, no 52, p. 9073-9076Article in journal (Refereed)
  • 16.
    Frigell, Jens
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Cumpstey, Ian
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of carbadisaccharide mimics of galactofuranosides2009In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 50, no 36, p. 5142-5144Article in journal (Refereed)
  • 17.
    Hoben, Christine E.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kanupp, Lisa
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Practical chemoenzymatic dynamic kinetic resolution of primary amines via transfer of a readily removable benzyloxycarbonyl group2008In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 49, no 6, p. 977-979Article in journal (Refereed)
  • 18. ibrahem, Ismail
    et al.
    Samec, Joseph S M
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Bäckvall, Jan-E
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdiva, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Enantioselective addition of aldehydes to amines via combined catalytic biomimetic oxidation and organocatalytic C-C- bond formation2005In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 46, no 23, p. 3965-3968Article in journal (Refereed)
    Abstract [en]

    The biomimetic catalytic enantioselective addition of aldehydes to amines is reported. This was accomplished by combining biomimetic coupled catalytic aerobic oxidation of amines involving ruthenium-induced dehydrogenation and organocatalytic asymmetric Mannich reactions. The novel one-pot reactions furnished β-amino aldehyde and α-amino acid derivatives in high yields with excellent chemoselectivity and up to >99% ee.

  • 19.
    Jönsson, Daniel
    et al.
    Stockholm University, Faculty of Science, Department of Neurochemistry and Neurotoxicology.
    Erlandsson, Mikael
    Stockholm University, Faculty of Science, Department of Neurochemistry and Neurotoxicology.
    Undén, Anders
    Stockholm University, Faculty of Science, Department of Neurochemistry and Neurotoxicology.
    Solid-phase synthesis of oxygen-bridged tetrahydropyridones2001In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 42, no 39, p. 6953-6956Article in journal (Refereed)
    Abstract [en]

    A solid-phase approach for the synthesis of oxygen-bridged tetrahydropyridones has been developed. A diamine is attached to Trt-Cl resin and condensed with different aliphatic or aromatic ketones and coumarin-3-carboxylic acid for 20 h and cleaved with 5% TFA in DCM, resulting in tri or tetracyclic products in moderate to high yield.

  • 20.
    Kjellgren, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J.
    Synthesis of stereodefined vinyl-tetrahydropyran and vinyl-octahydrochromene derivatives via acetalization-cyclization of allylsilanes with aldehydes: Origin of the high stereoselectivity2002In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 43, no 6, p. 1123-1126Article in journal (Refereed)
  • 21. Linde, Christian
    et al.
    Anderlund, Magnus
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Åkermark, Björn
    The Effect of Phenolates in the Mn(salen)-Catalyzed Epoxidation Reaction2005In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 46, no 33, p. 5597-5600Article in journal (Refereed)
    Abstract [en]

    By addition of 2,4,6-tri-tert-butylphenolate in the Mn(salen) catalyzed epoxidation of cis-alkenes with iodosobenzene, essentially pure trans-epoxides can be obtained.

  • 22.
    Lindström, Ulf M.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Somfai, Peter
    Microwave-assisted aminolysis of vinylepoxides1999In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 40, no 52, p. 9273-9276Article in journal (Refereed)
    Abstract [en]

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

  • 23.
    Lundberg, Helena
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Adolfsson, Hans
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ruthenium-catalyzed asymmetric transfer hydrogenation of ketones in ethanol2011In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 52, no 21, p. 2754-2758Article in journal (Refereed)
    Abstract [en]

    A ruthenium catalyst formed in situ by combining [Ru(p-cymene)Cl2]2 and an amino acid hydroxy-amide was found to catalyze efficiently the asymmetric reduction of aryl alkyl ketones under transfer hydrogenation conditions using ethanol as the hydrogen donor. The secondary alcohol products were obtained in moderate to good yields and with good to excellent enantioselectivity (up to 97% ee).

  • 24.
    Motwani, Hitesh V.
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK). Kyushu University, Japan.
    Shimakoshi, Hisashi
    Golding, Bernard T.
    Törnqvist, Margareta
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Hisaeda, Yoshio
    Alkylcobyrinate from sucralose and mechanistic aspects of its Co-C bond cleavage2014In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 55, no 16, p. 2667-2670Article in journal (Refereed)
    Abstract [en]

    Reaction of heptamethyl cob(I)yrinate with 1',6'-dichloro-1',6'-dideoxy-beta-D-fructofuranosyl-4-chloro-4-deoxy-alpha-D-galactopyranoside (sucralose) gave an alkylcobyrinate, heptamethyl-6'-[alpha-D-galactopyranoside- 1'-chloro-1',6'-dideoxy-beta-D-fructofuranosyl-4-chloro-4-deoxy]cobyrinate perchlorate, [(Suc)Cob(III) 7C(1)ester]ClO4. Cleavage behavior of Co-C bond of the alkylcobyrinate was investigated under various conditions (hv, H+ and reduction) using UV-vis spectroscopy combined with the EPR spin-trapping technique, and by cyclic voltammetry.

  • 25.
    Olofsson, Berit
    et al.
    Royal Institute of Technology, Sweden.
    Somfai, Peter.
    Royal Institute of Technology, Sweden.
    Determination of the relative configuration of vic-amino alcohols2003In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 44, no 6, p. 1279-1281Article in journal (Refereed)
    Abstract [en]

    A large set of syn- and anti-1,2-amino alcs. has been synthesized. Upon comparison of the CHO and CHN 1H NMR shifts a general trend has been obsd., making it possible to det. the relative configuration of 1,2-amino alcs. without derivatization or shift reagents.

  • 26.
    Rosenthal, Katri
    et al.
    Stockholm University, Faculty of Science, Department of Neurochemistry and Neurotoxicology.
    Erlandsson, Mikael
    Stockholm University, Faculty of Science, Department of Neurochemistry and Neurotoxicology.
    Undén, Anders
    Stockholm University, Faculty of Science, Department of Neurochemistry and Neurotoxicology.
    4-(3-Hydroxy-4-methylpentyl)phenylacetic acid as a new linker for the solid phase synthesis of peptides with Boc chemistry1999In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 40, no 2, p. 377-380Article in journal (Refereed)
    Abstract [en]

    The anchoring the first amino acid in Boc chemistry to a 4-(3-hydroxy-4-methylpentyl)phenylacetic acid linker is described and compared to the conventional Pam resin. The peptidyl-4-(4-methyl-3-pentoxy)phenylacetamide linkage is slightly more stable to TFA than the Pam linker but in contrast to the Pam linker stable to cleavage of benzylic protective groups with TFMSA/DMS/TFA mixtures. This allows a mild and convenient two step deprotection procedure using the “low TFMSA-high HF”. In HF this new linker reacts preferentially in an intramolecular reaction forming a tetrahydronaphthalene derivative.

  • 27.
    Stamatov, Stephan D.
    et al.
    -.
    Stawinski, Jacek
    Stockholm University, Faculty of Science, Department of Organic Chemistry. -.
    Regioselective and stereospecific opening of an oxirane system mediated by trifluoroacetic acid and halide anions. A new direct approach to C3-vicinal halohydrins.: -2007In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, ISSN -, Vol. 48, no -, p. 1887-1889Article in journal (Refereed)
    Abstract [en]

    -

  • 28.
    Thalén, Lisa K.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Hedberg, Martin H.
    Bäckvall, Jan-E.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Recycling of pipecoloxylidide via racemization2010In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 51, no 52, p. 6802-6805Article in journal (Refereed)
    Abstract [en]

    A method for the racemization of pipecoloxylidide with a ruthenium catalyst has been developed. This racemization method can be implemented in an integrated process that combines the separation of two enantiomers with racemization of the undesired enantiomer.

  • 29.
    Vesely, Jan
    et al.
    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.
    Aza-Morita-Baylis-Hillman-type reactions: highly enantioselective organocatalytic addition of unmodified alpha-beta-unsaturated aldehydes to N-Boc protected imines2007In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 48, no 39, p. 6900-6904Article in journal (Refereed)
    Abstract [en]

    Highly enantioselective catalytic routes to Boc protected aza-Morita-Baylis-Hiliman-type products are presented. The organocatalytic asymmetric reactions between unmodified alpha,beta-unsaturated aldehydes and N-Boc protected aryl imines proceed with excellent chemo- and enantioselectivity to give the corresponding compounds in good yields with 97-99% ee

  • 30.
    Wahlström, Karolina
    et al.
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    Planstedt, Ove
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    Undén, Anders
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    A carbamoyl-protective group for tyrosine that facilitatespurification of hydrophobic synthetic peptides2008In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 49, no 23, p. 3779-3781Article in journal (Refereed)
  • 31.
    Wahlström, Karolina
    et al.
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    Planstedt, Ove
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    Undén, Anders
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    Synthesis and purification of aggregation-prone hydrophobicpeptides by the incorporation of an Fmoc dipeptide withthe peptide bond protected with a modified 2-hydroxy-4-methoxybenzyl (Hmb) group2008In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 49, no 24, p. 3921-3924Article in journal (Refereed)
    Abstract [en]

    The dipeptide Fmoc-Val-(2-hydroxy-4-methoxybenzyl)Gly-OBzl was synthesized and the 2-hydroxyl group carbamoylated to give a Boc-N(CH(3))CH(2)CH(2)N(CH(3))CO-, (Boc-Nmec-) modification of the 2-hydroxy-4-methoxybenzyl (Hmb) group. After catalytic hydrogenation and purification, the resulting dipeptide Fmoc-Val-(Boc-Nmec-Hmb)Gly-OH was used in solid phase peptide synthesis. During treatment with TFA, the peptide was released from the resin and the Boc group cleaved. The peptide could then be purified with an alkylated peptide bond carrying a cationic charge that both increased the solubility of the peptide during the purification steps and facilitated analysis by MALDI-TOF mass spectrometry. The Nmec group was cleaved by intramolecular cyclization under slightly alkaline conditions, followed by cleavage of the Hmb group by TFA to give the fully deprotected peptide.

  • 32.
    Wahlström, Karolina
    et al.
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    Undén, Anders
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    A new protecting group for tryptophan in solid-phase peptide synthesis which protectsagainst acid-catalyzed side reactions and facilitates purification by HPLC2009In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 50, no 24, p. 2976-2978Article in journal (Refereed)
    Abstract [en]

    The indole nucleus of Z-Trp-OBzl is modified by acylation of the indole nitrogen using Boc-N-methyl butyric acid followed by catalytic hydrogenation and introduction of the Fmoc group. The resulting derivative, Fmoc-Trp(Boc-Nmbu)-OH, is incorporated into peptide chains via solid-phase peptide synthesis (SPPS). After assembly of the peptide chain, the Boc group is cleaved by treatment with TFA. The peptide is isolated with the tryptophan residue modified with a cationic 4-(N-methylamino) butanoyl group, which improves the solubility of the peptide during HPLC purification. On treatment of the purified peptide at pH 9.5, the Nmbu group undergoes an intramolecular cyclization reaction; this results in the fully deprotected peptide and N-methylpyrrolidone.

  • 33. Wieczorek, Birgit
    et al.
    Träff, Annika
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Krumlinde, Patrik
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Dijkstra, Harm P.
    Egmond, Maarten R.
    van Koten, Gerard
    Bäckvall, Jan-Erling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Klein Gebbink, Robertus J. M.
    Covalent anchoring of a racemization catalyst to CALB-beads: towards dual immobilization of DKR catalysts2011In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 52, no 14, p. 1601-1604Article in journal (Refereed)
    Abstract [en]

    The preparation of a heterogeneous bifunctional catalytic system, combining the catalytic properties of an organometallic catalyst (racemization) with those of an enzyme (enantioselective acylation) is described. A novel ruthenium phosphonate inhibitor was synthesized and covalently anchored to a lipase immobilized on a solid support (CALB, Novozym® 435). The immobilized bifunctional catalytic system showed activity in both racemization of (S)-1-phenylethanol and selective acylation of 1-phenylethanol.

  • 34.
    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.

  • 35.
    Zhu, Mingzhao
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lin, Shuangzheng
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhao, Gui-Ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sun, Junliang
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Organocatalytic diastereoselective dibromination of alkenes2010In: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 51, no 20, p. 2708-2712Article in journal (Refereed)
    Abstract [en]

    A highly diastereoselective pyrrolidine-promoted dibromination of alkenes by combination of NBS and succinimide is presented. The pyrrolidine-mediated dibromination of alkenes is higly anti-selective and gives the corresponding products in moderate to high yields and up to >25:1 dr.

1 - 35 of 35
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