Jan Dahmén

Synthesis of di-, tri-, and tetra-saccharides corresponding to receptor structures recognised by Streptococcus pneumoniae

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.

Synthesis of spacer-arm, lipid, and ethyl glycosides of the trisaccharide portion [α-D-Gal-(1→4)-β-D-Gal-(1→4)-β-D-Glc] of the blood-group Pk antigen: preparation of neoglycoproteins

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.

X-ray crystal structure of galabiose, O-α-d-galactopyranosyl-(1→4)-d-galactopyranose

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-3C-4O-1′C-1′) = −81.9(3)°, φ H (H-1′C-1′O-1′C-4) = −18°, and ψ H (H-4C-4O-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-3H · · · 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-5C-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.

4-O-α-d-galactopyranosyl-d-galactose: Efficient synthetic routes from “polygalacturonic acid”

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.

2-bromoethyl glycosides in glycoside synthesis: Preparation of glycoproteins containing α-l-Fuc-(1→2)-d-Gal and β-d-Gal-(1→4)-d-GlcNAc☆

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).

Synthesis of spacer-ARM, lipid, and ethyl glycosides of the terminal trisaccharide [α-D-Gal-(1→4)-β-D-Gal-(1→4)-β-D-GlcNAc] portion of the blood-group P1 antigen: preparation of neoglycoproteins

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.

Virtual long-range coupling of the anomeric proton of carbohydrates: An n.m.r. spin-simulation study

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

Amotin and amoenin, two sesquiterpenes of the picrotoxane group from Dendrobium amoenum

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.

The structure of parishin, a glucoside from Vanda parishii

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.

Synthesis from pullulan of spacer-arm, lipid, and ethyl glycosides of a tetrasaccharide [α-d-Glc-(1→6)-α-d-Glc-(1→4)-α-d-Glc-(1→4)-d-Glc] found in human urine; preparation of neoglycoproteins

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.