Jan Dahmén
Stockholm University
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Featured researches published by Jan Dahmén.
Carbohydrate Research | 1985
Jan Dahmén; Gösta Gnosspelius; Ann-Charlott Larsson; Thomas Lave; Ghazi Noori; Karin P»lsson; Torbjörn Frejd; Göran Magnusson
Abstract Syntheses are described for methyl 2-acetamido-2-deoxy-4- O -β- d -galactopyranosyl-α- d -glucopyranoside, methyl 2-acetamido-2-deoxy-4- O -β- d -galactopyranosyl-β- d -glucopyranoside, methyl 3- O -(2-acetamido-2-deoxy-β- d -glucopyranosyl-β- d -galactopyranoside, methyl 3- O -(2-acetamido-2-deoxy-4- O -β- d -galactopyranosyl-β- d -glucopyranosyl)-β- d -galactopyranoside, and methyl 4- O -[3- O -(2-acetamido-2-deoxy-4- O -β- d -galactopyranosyl-β- d -glucopyranosyl)-β- d -galactopyranosyl]- β- d -glucopyranoside.
Carbohydrate Research | 1984
Jan Dahmén; Torbjörn Frejd; Göran Magnusson; Ghazi Noori; Anne-Sofie Carlström
Abstract The title compounds were prepared via the acetylated 2-bromoethyl glycoside 11 of α- d -Gal-(1→4)-β- d -Gal-(1→4)-β- d -Glc by displacement of bromide ion with methyl 3-mercaptopropionate, octadecanethiol, and hydrogen, respectively. Silver triflate-promoted glycosylation of 2-bromoethyl 2,3,6-tri-O-benzyl-β- d -glucopyranoside with 2,3,6-tri-O-acetyl-4-O-(2,3,4,6-tetra-O-acetyl-α- d -galactopyranosyl)-α- d -galactopyranosyl bromide gave 11. A tetradeuterated analogue of 11 was prepared by essentially the same route. The spacer-arm glycoside formed from methyl 3-mercaptopropionate was coupled to bovine serum albumin and keyhole limpet haemocyanin.
Carbohydrate Research | 1986
Göran Svensson; Jörgen Albertsson; Christer Svensson; Göran Magnusson; Jan Dahmén
Abstract O -α- d -Galactopyranosyl-(1→4)- d -galactopyranose, C 12 H 22 O 11 , M r = 342.30, crystallises in the orthorhombic space group P 2 1 2 1 2 1 , and has a = 5.826(1), b = 13.904(3), c = 17.772(4) A, Z = 4, and D x = 1.579 g.cm −3 . Intensity data were collected with a CAD4 diffractometer. The structure was solved by direct methods and refined to R = 0.063 and R w = 0.084 for 2758 independent reflections. The glycosidic linkage is of the type 1-axial-4-axial with torsion angles φ O-5′ (O-5′C-1′O-1′C-4) = 98.1(2)°, ψ C-3 (C-3C-4O-1′C-1′) = −81.9(3)°, φ H (H-1′C-1′O-1′C-4) = −18°, and ψ H (H-4C-4O-1′C-1′) = 35°. The conformation is stabilised by an O-3 · · · O-5′ intramolecular hydrogen-bond with length 2.787(3) A and O-3H · · · O-5′ = 162°. The glycosidic linkage causes a folding of the molecule with an angle of 117° between the least-square planes through th pyranosidic rings. The crystal investigated contained 56(1)% of α- and 44(1)% of β-galabiose as well as ∼70% of the gauche-trans and ∼30% of the trans-gauche conformers about the exocyclic C-5′C-6′ and C-5C-6 bonds. The crystal packing is governed by hydrogen bonding that engages all oxygen atoms except the intramolecular acceptor O-5′ and the glycosidic O-1′ oxygen atoms.
Carbohydrate Research | 1983
Jan Dahmén; Torbjörn Frejd; Thomas Lave; Frank Lindh; Göran Magnusson; Ghazi Noori; Karin P»lsson
Abstract Enzymic hydrolysis of “polygalacturonic acid” gave a mixture of oligomers which was fractionated by ion-exchange chromatography. The resulting di- and tri-saccharides were treated, respectively, with methanol and ethylene oxide, and the resulting esters were reduced with sodium borohydride. Treatment of the products with acetic anhydride and sulfuric acid, followed by deacetylation, produced the title compound.
Carbohydrate Research | 1984
Jan Dahmén; Torbjörn Frejd; Göran Magnusson; Ghazi Noori; Anne-Sofie Carlström
Abstract The applicability of 2-bromoethyl glycosides in carbohydrate synthesis is demonstrated by the synthesis of glycosides of α- l -Fuc-(1→2)- d -Gal and β- d -Gal(1→4)- d -GlcNAc. The bromoethyl aglycon was transformed into the methoxycarbonylethylthioethyl spacer, which allowed coupling of the sugars to proteins (BSA and KLH).
Carbohydrate Research | 1984
Jan Dahmén; Torbjörn Frejd; Göran Magnusson; Ghazi Noori; Anne-Sofie Carlström
Abstract The title compounds were prepared via the acetylated 2-bromoethyl β-glycoside ( 5 ) of α- d -Gal-(1→4)-β- d -Gal-(1→4)-β- d -GlcNAc by displacement of bromide ion with methyl 3-mercaptopropionate, octadecanethiol, and hydrogen, respectively. Silver triflate-promoted glycosylation of 2-bromoethyl 3,6-di- O -benzyl-2-deoxy-2-phthalimido-β- d -glucopyranoside with 2,3,6-tri- O -acetyl-4- O -(2,3,4,6-tetra- O -acetyl-α- d -galactopyranosyl)-α- d -galactopyranosyl bromide gave 5 . The spacer-arm glycoside derived from methyl 3-mercaptoproprionate was coupled to bovine serum albumin and key-hole limpet haemocyanin to give neo-glycoproteins.
Carbohydrate Research | 1984
Jan Dahmén; Torbjörn Frejd; Gunnar Grönberg; Göran Magnusson; Ghazi Noori
Table des valeurs calculees et experimentales des constantes couplage spin spin des protons anomeres de glycosides. La determination des deplacements chimiques et des constantes de couplage a ete faite par des techniques de double resonance et de RMN a 2 dimensions
Phytochemistry | 1978
Jan Dahmén; Kurt Leander
Abstract Two new sesquiterpenes, amotin and amoenin, of the picrotoxane group were isolated from Dendrobium amoenum . The constitution of amoenin was evident from spectral investigations and by its conversion into α-dihydro-picrotoxinin on oxidation with oxygen in the presence of platinum. The constitution of amotin was shown by its spectral properties and the conversion of aduncin into amotin by hydrogenolysis of its epoxide ring. That the configuration at C-4 in aduncin and amotin is R was supported by circular dichroism measurements on some derivatives of picrotoxinin and aduncin.
Phytochemistry | 1976
Jan Dahmén; Kurt Leander
Abstract Two new glucosides, tris [4-(β- D -glucopyranosyloxy)benzyl] citrate, named parishin, and 4-(β- D -glucopyranosyloxy)benzyl alcohol have been isolated from Vanda parishii . The latter compound may, however, be an artefact formed from parishin.
Carbohydrate Research | 1984
Jan Dahmén; Torbjörn Frejd; Göran Magnusson; Ghazi Noori; Anne-Sofie Carlström
Abstract Enzymic hydrolysis of pullulan, followed by acetylation and chromatography, gave acetylated α- d -Glc p -(1→6)-α- d -Glc p -(1→4)-α- d -Glc p -(1→4)- d -Glc p which, with 2-bromoethanol and boron trifluoride etherate in dichloromethane, gave the 2-bromoethyl glycoside. The reactions of the glycoside with methyl 3-mercaptopropionate, methyl 11-mercaptoundecanoate, and octadecanethiol are described, and also its hydrogenolysis to give an ethyl glycoside. The mercaptopropionate-derived, spacer-arm glycoside has been coupled to bovine serum albumin and keyhole limpet haemocyanin.