Herbicidin congeners, undecose nucleosides from an organic extract of Streptomyces sp. L-9-10.

Four new undecose nucleosides (herbicidin congeners), three known herbicidins, and 9-(ß-d-arabinofuranosyl)hypoxanthine (Ara-H) were isolated from the organic extract of a fermentation culture of Streptomyces sp. L-9-10 using proton NMR-guided fractionation. Their structures were elucidated on the basis of comprehensive 1D and 2D NMR and mass spectrometry analyses. These structures included 2'-O-demethylherbicidin F (1), 9'-deoxy-8',8'-dihydroxyherbicidin B (2), 9'-deoxy-8'-oxoherbicidin B (2a), and the 8'-epimer of herbicidin B (3). This is the first detailed assignment of proton and carbon chemical shifts for herbicidins A, B, and F. The isolated compounds were evaluated for cancer chemopreventive potential based on inhibition of tumor necrosis factor alpha (TNF-α)-induced nuclear factor-kappa B (NF-κB) activity.

CD and NMR assignment of the anomeric configuration of 4-(5-deoxy-alpha,beta-l-arabinofuranosyl)-2-phenyl-2H-1,2,3-triazole C-nucleoside analogs.

Acid-catalyzed dehydrative cyclization of 5-deoxy-L-manno-pentitol-1-yl)-2-heptulose bisphenylhydrazone and subsequent reflux with copper sulfate gave an anomeric mixture of 4-(5-deoxy-alpha,beta-L-arabinofuranosyl)-2-phenyl-2H-1,2,3-triazole C-nucleoside analogs. The mixture was separated by chromatography, and the anomeric compositions configurations of the components were determined by CD, NMR, mass spectroscopy, and acylation.

Arabinofuranosides from mycobacteria: synthesis of a highly branched hexasaccharide and related fragments containing beta-arabinofuranosyl residues.

The synthesis of 11 oligosaccharides (4-14) containing beta-arabinofuranosyl residues is reported. The glycans are all fragments of two polysaccharides, arabinogalactan and lipoarabinomannan, which are found in the cell wall complex of mycobacteria. In the preparation of the targets, the key step was a low-temperature glycosylation reaction that installed the beta-arabinofuranosyl residues with good to excellent stereocontrol.

Synthesis of 9-(beta-D-arabinofuranosyl)guanine using whole cells of Escherichia coli.

Synthesis of 9-(beta-D-arabinofuranosyl)guanine (ara-G) from 1-(beta-D-arabinofuranosyl)cytosine (ara-C) and guanine, guanosine or 2'-deoxyguanosine (dG) by glutaraldehyde-treated Escherichia coli BM-11 cells is described. It is shown that the concentration of phosphate ions, molar ratio of substrates and pH of the reaction medium are factors affecting product yield. Under optimum conditions ara-G was produced in the reaction mixture in a yield of 63%-65% based on dG as the best source of guanine base. The yield of isolated ara-G was 48%-53%.

Structural studies of the carbohydrate moieties of lectins from potato (Solanum tuberosum) tubers and thorn-apple (Datura stramonium) seeds.

1. Methylation analysis of potato (Solanum tuberosum) lectin and thorn-apple (Datura stramonium) lectin confirmed previous conclusions that both glycoproteins contained high proportions of l-arabinofuranosides and lesser amounts of d-galactopyranosides. The arabinofuranosides are present in both lectins as short unbranched chains containing 1-->2- and 1-->3-linkages, which are known to be linked to hydroxyproline. Galactopyranosides are present as monosaccharides, which are known to be attached to serine, in potato lectin and as both the monosaccharide and the 1-->3-linked disaccharide in Datura lectin. 2. Alkaline digestion of potato lectin and subsequent separation of the components by gel filtration led to the isolation of four fractions corresponding to the mono-, di-, tri- and tetra-arabinosides of hydroxyproline. The latter two fractions accounted for over 70% of the total hydroxyproline. 3. Methylation analysis was used to show that the triarabinoside contained only 1-->2-linkages between sugars, but that the tetra-arabinoside contained both 1-->2- and 1-->3-linkages. Direct-insertion mass spectrometry of these compounds using electron impact and chemical ionization, in a comparison with other known structural patterns, was used to determine the sequences of the sugars, which were Araf1-->2Araf1-->2Araf1-->Hyp and Araf1-->3Araf1-->2Araf1-->2Araf 1-->Hyp. 4. On the basis of optical rotation it had previously been suggested [Allen, Desai, Neuberger & Creeth (1978) Biochem. J.171, 665-674] that all the arabinose of potato lectin was present as the beta-l-furanoside. However, measurement of the optical rotations of the hydroxyprolyl arabinosides showed that whereas the diarabinoside had a molar rotation ([m]) value close to that predicted, the triarabinoside was more dextrorotatory and the tetra-arabinoside was less dextrorotatory than expected. Possible explanations for these findings are that, although the di- and tri-arabinosides contain exclusively beta-arabinofuranosides, in the tri-arabinoside, interactions between pentose units lead to an enhanced positive rotation. The tetra-arabinoside, however, is proposed to contain a single alpha-arabinofuranoside residue, which is responsible for the lower than expected positive rotation. The observed rotation of the tetra-arabinoside was found to be close to the theoretical value predicted on that basis. Furthermore, the action of a specific alpha-arabinofuranosidase on the tetrasaccharide was to remove a single arabinose residue, presumably the terminal non-reducing sugar, and to produce a product that was indistinguishable on electrophoresis from the triarabinoside. Changes in rotation were compatible with this assumption. 5. It is concluded that the structures of the hydroxyprolyl tri- and tetra-arabinosides of potato lectin are: betaAraf1-->2betaAraf1-->2betaAraf1-->Hyp and alphaAraf1-->3betaAraf1-->2betaAraf 1-->2betaAraf1-->Hyp. These are identical with compounds that have been isolated from the insoluble hydroxyproline-rich glycoproteins of plant cell walls.