Volker Sinnwell

Darstellung selektiv blockierter 2-azido-2-desoxy-D-gluco- und -D-galactopyranosylhalogenide: reaktivität und 13C-NMR-spektren

Abstract The synthesis of several 2-azido-2-deoxy- D -gluco- and - D -galactopyranosyl halides is described. With tetraethylammonium chloride, α-pyranosyl bromides react to give β-pyranosyl chlorides. This provides a facile method for obtaining selectively blocked halides for the synthesis of α-linked, amino sugar of oligosaccharides. The inversion reaction at the anomeric centre is shown to be of second order, corresponding to an S N 2 mechanism. The rates of the inversion reactions were correlated to the 13C-n.m.r. data of C-1 of α-bromides. Within the gluco series, the 13C-n.m.r. shift of C-1 proves to be proportional to the natural logarithm of the rate constant. An analogous correlation in the galacto series could not be observed.

Isolation and chemical analysis of 7-O-(2-amino-2-deoxy-α-d-glucopyranosyl)-l-glycero-d-manno-heptose as a constituent of the lipopolysaccharides of the UDP-galactose epimerase-less mutant J-5 of Escherichia coli and Vibrio cholerae

Methyl 7-O-(2-amino-2-deoxy-alpha-D-glucopyranosyl)-L-glycero-D-manno-hepto+ ++ pyranoside (1) was released from the lipopolysaccharide of the UDP-galactose epimerase-less mutant J-5 of Escherichia coli by methanolysis and isolated by high-voltage paper electrophoresis. Its chemical structure was determined by chemical analysis, deamination with nitrous acid, g.1.c.-m.s., and 1H- and 13C-n.m.r. spectroscopy performed on its acetylated derivative. The disaccharide moiety of 1 was also detected in lipopolysaccharides of Vibrio cholerae.

Cysteine-glutathione disulfide, the sperm-release pheromone of the marine polychaete Nereis succinea (Annelida: Polychaeta)

Summary. In the marine polychaete Nereis succinea (Frey & Leuckart 1847) a sex pheromone was isolated from the coelomic fluid of sexually mature females and identified by NMR studies and independent synthesis. This pheromone is released by the females during reproduction together with eggs and coelomic fluid into the free water column and induces sperm release of surrounding males. Its structure was ascertained as L-cysteine-glutathione disulfide. It exhibited a response threshold of 0.6 · 10−7 M.

New bacterial degradation of the biaryl ether structure

We report here the oxygenolytic cleavage of the ether bond occurring as the initial enzymatic step of high regioselectivity in the course of the bacterial attack on such aromatic compounds. Their complete catabolism is achieved by subsequent cleavage of the aromatic rings and further known reactions

Konformationsanalyse der verzweigten pentasaccharid-sequenz der “bisected” struktur von N-glycoproteinen

In the conformational analysis of the pentasaccharide alpha-D-Manp-(1----3)-[beta-D-GlcpNAc-(1----4)]-[alpha-D- Manp-(1----6)]-beta-D-Manp-(1----4)-D-GlcNAc, which represents the essential core structure within the bisected type of N-glycoproteins, n.m.r. experiments and GESA calculations indicated that a gg conformation is preferred for the (1----6)-glycosidic linkage. This is in contrast to the results obtained for the tetrasaccharide alpha-D-Manp-(1----3)-[alpha-D-Manp-(1----6)]-beta-D- Manp-(1----4)- D-GlcNAc, which indicated that a gt conformation with the (1----6)-linked alpha-D-mannose group folded back is preferred. The conformations of the remaining glycosidic linkages in the tetra- and penta-saccharide are similar.

Essential oil composition of Smyrnium olusatrum

The essential oils obtained by hydrodistillation of green and ripe fruits, herb, flowers and roots of Smyrnium olusatrum (alexanders), have been analyzed by means of GC, GC-MS, and NMR spectroscopic methods. Roots, herb and flowers are characterized by a high content of oxygenated sesquiterpenoids, most of them furanosesquiterpenoids, while green and ripe fruits are dominated by monoterpene hydrocarbons with beta-phellandrene and alpha-pinene as major constituents. The furanosesquiterpenoids, comprising a high proportion of furanodiene and isofuranogermacrene, are present in all parts of the plant. In roots and herbs furanoeremophil-1-one is the second important furanosesquiterpenoid, whereas 1beta-acetoxyfurano-4(15)-eudesmene was detected as a prominent component in green and ripe fruits. Additionally a new furanoeudesmane derivative has been isolated from the fruits. With the aid of (13)C, (1)H and 2D NMR the structure has been established as furano-4(15)-eudesmen-1-one.

Myrmicarin 430A: a new heptacyclic alkaloid from Myrmicaria ants

A heptacyclic alkaloid, myrmicarin 430A. showing an entirely new carbon skeleton made up two unbranched C15-chains, is identified from the poison gland secretion of African Myrmicaria ants by NMR spectroscopy.

Biotransformation of diphenyl ether by the yeastTrichosporon beigelii SBUG 752

Trichosporon beigelii SBUG 752 was able to transform diphenyl ether. By TLC, HPLC, GC, GC-MS, NMR- and UV-spectroscopy, several oxidation products were identified. The primary attack was initiated by a monooxygenation step, resulting in the formation of 4-hydroxydiphenyl ether, 2-hydroxydiphenyl ether and 3-hydroxydiphenyl ether (48:47:5). Further oxidation led to 3,4-dihydroxydiphenyl ether. As a characteristic product resulting from the cleavage of an aromatic ring, the lactone of 2-hydroxy-4-phenoxymuconic acid was identified. The possible mechanism of ring cleavage to yield this metabolite is discussed.

Isolation and characterization of the tetrasaccharide (bis)phosphate from the glycosyl backbone of Salmonella Minnesota and Escherichia coli re-mutant lipopolysaccharides

Abstract Intact tetrasaccharide mono- ( 1 ) and bisphosphates ( 2 ) were isolated from deep rough mutant strains of Salmonella minnesota (mutant R595) and Escherichia coli (mutant F515) and their chemical structure was unequivocally characterized by 1 H-, 13 C- and 31 P-NMR spectrometry and FAB-MS and chemical analysis as 1 and 2

Untersuchung der 13c-kernresonanz-spektren der acht isomeren 1,6-anhydro-β-D-hexopyranosen

Abstract The signals of the 13 C-n.m.r. spectra of the eight isomeric 1,6-anhydro-β- D -hexopyranoses having the 1 C 4 conformation were assigned by comparison with the spectra of selectively deuterated derivatives and by observation of the substituent effect of the O -isopropylidene derivatives. Of the two substituted C atoms in the O -isopropylidene derivatives, the signal of the equatorially substituted C atom was shifted to a lower field more strongly than that of the carbon atom bearing an axial substituent. The chemical shifts and their calculation with empirical parameters are discussed.