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  • 1.
    Angles d'Ortoli, Thibault
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Synthesis of the tetrasaccharide glycoside moiety of Solaradixine and rapid NMR-based structure verification using the program CASPER2016Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 72, nr 7, s. 912-927Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The major glycoalkaloid in the roots of Solanum laciniatum is Solaradixine having the branched tetrasaccharide beta-D-Glcp-(1 -> 2)-beta-D-Glcp-(1 -> 3)[alpha-L-Rhap-(1 -> 2)]-beta-D-Galp linked to O3 of the steroidal alkaloid Solasodine. We herein describe the synthesis of the methyl glycoside of the tetrasaccharide using a super-armed disaccharide as a donor molecule. A 2-(naphthyl)methyl protecting group was used in the synthesis of the donor since it was tolerant to a wide range of reaction conditions. The 6-O-benzylated-hexa-O-tert-butyldimethylsilyi-protected beta-D-Glcp-(1 -> 2)-beta-D-Glcp-SEt donor, which avoided 1,6-anydro formation, was successfully glycosylated at O3 of a galactoside acceptor molecule. However, subsequent glycosylation at O2 by a rhamnosyl donor was unsuccessful and instead a suitably protected alpha-L-Rhap(1 -> 2)-beta-D-Galp-OMe disaccharide was used as the acceptor molecule together with a super-armed beta-D-Glcp-(1 -> 2)-beta-D-Glcp-SEt donor in the glycosylation reaction, to give a tetrasaccharide in a yield of 55%, which after deprotection resulted in the target molecule, the structure of which was verified by the NMR chemical shift prediction program CASPER.

  • 2. Barbion, Julien
    et al.
    Sorin, Geoffroy
    Selkti, Mohamed
    Kellenberger, Esther
    Baati, Rachid
    Santoro, Stefano
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Himo, Fahmi
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Pancrazi, Ange
    Lannou, Marie-Isabelle
    Ardisson, Janick
    Stereoselective functionalization of pyrrolidinone moiety towards the synthesis of salinosporamide A2012Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 68, nr 32, s. 6504-6512Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An important feature of the synthesis of salinosporamide A. a potent proteasome inhibitor, is the establishment of the quaternary stereocenter at C3. A new route has been developed based on the methylation of a functionalized pyrrolidinone. Direct methylation reaction led to the unwanted diastereomer: however, by means of a Corey-Chaykovsky reaction followed by LiAlH4 epoxide opening, the desired alcohol was obtained. The pyrrolidinone was elaborated through a key allylation reaction between a tertiary allyltitanium reagent and an aldehyde bearing a spiroketal moiety in alpha-position.

  • 3.
    Brea, Oriana
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Daver, Henrik
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Rebek, Julius
    Himo, Fahmi
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Mechanism(s) of thermal decomposition of N-Nitrosoamides: A density functional theory study2019Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 75, nr 8, s. 929-935Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The thermal decomposition of N-nitrosoamides has experimentally been demonstrated to depend on several factors, such as temperature, solvent and the substituents on the substrate. Consequently, a number of reaction mechanisms have been proposed for this process in the literature. In this work, we present a comprehensive computational investigation in which we examine the detailed reaction mechanisms for two N-nitrosoamides (with aliphatic and aromatic substituents) in two different solvents (mesitylene and methanol). It is shown that the reaction mechanism can change dramatically with the nature of the substrate and the choice of solvent. Importantly, it is found that the polar solvent stabilizes ion-pairs that are unstable in the non-polar solvent, which can play a key role in the mechanism.

  • 4. Cotton, Hanna K.
    et al.
    Norinder, Jakob
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Screening of Ligands in the Asymmetric Metallocenethiolatocopper(I)-Catalyzed Allylic Substitution with Grignard Reagents2006Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 62, nr 24, s. 5632-5640Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Screening of metallocenethiolate ligands for copper(I)-catalyzed substitution of allylic acetates with Grignard reagents has been carried out. The previously used ligand, lithium (R,Sp)-2-(1-dimethylaminoethyl)ferrocenylthiolate (4a), possessing both central and planar chirality, was the starting point for the screening. It was found that the diastereomeric ligand lithium (R,Rp)-2-(1-dimethylaminoethyl)ferrocenylthiolate (4b) exhibiting reversed planar chirality gave increased enantioselectivity in the allylic substitution, at least when cinnamyl acetate was used as a substrate. The ruthenocene-based ligand lithium (R,Sp)-2-(1-dimethylaminoethyl)ruthenocenylthiolate (4c) gave an enhanced reaction rate, but lower chiral induction. The use of disulfide bis[(R,Sp)-2-(1-dimethylaminoethyl)ferrocenyl]disulfide (7a) as a ligand precursor worked well but resulted in lower enantioselectivity.

  • 5. Cribiù, Riccardo
    et al.
    Borbas, K. Eszter
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Cumpstey, Ian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    On the synthesis of vinyl and phenyl C-furanosides by stereospecific debenzylative cycloetherification2009Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 65, nr 10, s. 2022-2031Artikel i tidskrift (Refereegranskat)
  • 6.
    Engström, Karin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Vallin, Michaela
    Hult, Karl
    Bäckvall, Jan-E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Kinetic resolution of diarylmethanols using a mutated variant of lipase CALB2012Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 68, nr 37, s. 7613-7618Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An enzymatic kinetic resolution of diarylmethanols via acylation has been developed. This was achieved by the use of a mutated variant of CALB that accepts larger substrates compared to the wild type. By the use of diarylmethanols with two differently sized aryl groups, enantioselective transformations were achieved. A larger size-difference led to a higher enantioselectivity. In addition, substrates with electronically different aryl groups, such as phenyl and pyridyl, also gave an enantioselective reaction. The highest E value was observed with a substrate where steric and electronic effects were combined.

  • 7. Fourniere, Viviane
    et al.
    Skantz, Linnea
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Sajtos, Ferenc
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Oscarson, Stefan
    Lahmann, Martina
    Synthesis of the Lewis b pentasaccharide and a HSA-conjugate thereof2010Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 66, nr 39, s. 7850-7855Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Helicobacter pylori, a gastric pathogen, binds to various blood group antigens, including the Lewis types, present in the gastric tissue and a relation between the presentation of the ligands and the overall strength of binding has been assumed. Synthetic Lewis b tetra- and hexasaccharide conjugates are available but not the analogous pentasaccharide. An efficient synthesis of the amino spacer equipped Lewis b pentasaccharide, 3-aminopropyl alpha-L-fucopyranosyl-(1 -> 2)-beta-D-galactopyranosyl-(1 3)-[alpha-L-fucopyranosyl-(1 -> 4)]-2-acetamido-2-deoxy-beta-D-glucopyranosyl-(1 -> 3)-beta-D-galactopyranoside, is presented to enable further investigation of the carbohydrate recognition process of H. pylori.

  • 8.
    Jalalian, Nazli
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Olofsson, Berit
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Design and asymmetric synthesis of chiral diaryliodonium salts2010Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 66, nr 31, s. 5793-5800Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The application of chiral hypervalent iodine reagents in asymmetric synthesis is highly desirable, as the reagents are metal-free, environmentally benign and employed under mild conditions. Three chiral diaryliodonium salts have been designed to provide chemoselectivity and asymmetric induction in asymmetric alpha-phenylation of carbonyl compounds. The synthetic routes to the selected targets are detailed herein, together with a structural investigation into the diastereoselectivity of the alkylation process.

  • 9.
    Janson, Pär G.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Ilchenko, Nadia O.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Diez-Varga, Alberto
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Szabó, Kálmán J.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Effects of B(2)pin(2) and PCy3 on copper-catalyzed trifluoromethylation of substituted alkenes and alkynes with the Togni reagent2015Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 71, nr 6, s. 922-931Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The copper-catalyzed oxytrifluoromethylation of phenylacetylenes and C-H trifluoromethylation of quinones were studied. It was found that both reactions are accelerated by B(2)pin(2) and PCy3 additives. The two reactions have different substituent effects. The oxytrifluoromethylation is faster in the presence of electron-donating groups, while the C-H trifluoromethylation is faster with electron-withdrawing substituents. The Hammett plot for oxytrifluoromethylation gave a rho value of 0.76 indicating electron demand in the rate determining step of the reaction. According to the absolute value of rho the reaction probably does not proceed through a rate determining formation of a carbocation intermediate. The kinetic isotope effect measurements indicate that in C-H trifluoromethylation of quinones the cleavage of the C-H bond is not the rate determining step of the reaction.

  • 10.
    Kalek, Marcin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Stawinski, Jacek
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Efficient synthesis of mono-and diarylphosphinic acids: a microwave-assisted palladium-catalyzed cross-coupling of aryl halides with phosphinate2009Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 65, nr 50, s. 10406-10412Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A general, efficient method for the microwave-assisted synthesis of mono- and diarylphosphinic acids from anilinium phosphinate and aryl halides, using Pd(0) and Xantphos as a supporting ligand, was developed.

  • 11.
    Lindquist, Charlotta
    et al.
    Organisk kemi, Avdelningen för kemi, KTH.
    Ersoy, Oguz
    Somfai, Peter
    Parallel synthesis of an indole-based library via an iterativeMannich reaction sequence2006Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 62, nr 14, s. 3439-3445Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A library of 1,3-disubstituted indoles has been prepared via an iterative Mannich reaction sequence. The first Mannich reaction with secondary amines and formaldehyde preferentially yields 3-aminomethyl indoles, while the second Mannich reaction introduces an additional aminomethyl group at the N1-position of the indole ring. A library of 25 substituted indoles has thus been prepared in moderate to good yields with purity.

  • 12. Nkambule, Comfort M.
    et al.
    Kwezi, Nomfundo W.
    Kinfe, Henok H.
    Nokwequ, Mbulelo G.
    Gammon, David W.
    Oscarson, Stefan
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Karlsson, Erik
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Efficient regioselective protection of myo-inositol via migration facile protecting group2011Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 67, nr 3, s. 618-623Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A cis-1,2-cyclohexanediol, 1,4,5,6-tetra-O-benzyl-myo-inositol, was selectively protected at the axial C2-hydroxyl via acid-mediated rearrangement of the corresponding 1,2-orthoacetate, or via the base-induced migration of a protecting group that had previously been easily installed with complete regioselectivity at the adjacent equatorial hydroxyl. Esters 4a-6a were synthesized in high yields (75-82%) while sulfonate 7a and silyl ether 8a were obtained in 85 and 31% yields, respectively. The migration of the esters induced by DBU results in equilibrium between regioisomers favouring the C2 protected isomer, but NaH induced migration of sulfonyl and silyl groups results in complete migration from equatorial to axial hydroxyl groups.

  • 13.
    Olofsson, Berit
    et al.
    Royal Institute of Technology, Sweden.
    Wijtmans, Roel
    Royal Institute of Technology, Sweden.
    Somfai, Peter.
    Royal Institute of Technology, Sweden.
    Synthesis of N-H vinylaziridines: a comparative study2002Ingår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 58, nr 30, s. 5979-5982Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Vinylaziridines are useful and versatile synthetic intermediates, as the relief of ring-strain provides a driving force for efficient ring-opening or ring-expansion reactions. Furthermore, the vinyl group can be derivatized into interesting functionalities. The ring-closure of vicinal amino alcs. constitutes a straightforward route to aziridines. Several methods exist for this transformation, although many cannot be applied to vinylaziridines due to their acid lability. This comparative study describes the most effective sequences for the formation of N-H vinylaziridines.

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