Probing Indole Diketopiperazine-Based Hybrids as Environmental-Induced Products from sp. EGF 15-0-3.

Comprehensive analyses of the metabolite spectra of sp. EGF 15-0-3 under different culture conditions revealed the presence of unique environmental-induced metabolites exclusively from the rice medium. Subsequent target isolation afforded four unprecedented indole diketopiperazine-based hybrids with a pyrano[3',2':7,8]isochromeno[4,3-]pyrazino[2,1-]indole core ( and ) or a spiro[piperazine-2,2'-pyrano[3,4,5-]chromene] scaffold ( and ).

The role of aromatic L-amino acid decarboxylase in bacillamide C biosynthesis by Bacillus atrophaeus C89.

For biosynthesis of bacillamide C by Bacillus atrophaeus C89 associated with South China sea sponge Dysidea avara, it is hypothesized that decarboxylation from L-tryptophan to tryptamine could be performed before amidation by the downstream aromatic L-amino acid decarboxylase (AADC) to the non-ribosomal peptide synthetases (NRPS) gene cluster for biosynthesizing bacillamide C. The structural analysis of decarboxylases' known substrates in KEGG database and alignment analysis of amino acid sequence of AADC have suggested that L-tryptophan and L-phenylalanine are the potential substrates of AADC. The enzymatic kinetic experiment of the recombinant AADC proved that L-tryptophan is a more reactive substrate of AADC than L-phenylalanine.

The resolution of aglinin A epimers and their NMR assignments.

Aglinin A (1) is a mixture of C(24)-epimeric 20S,24-epoxy-24,25-dihydroxy-3,4-secodammar-4(28)-en-3-oic acid and present in plants of the family Meliaceae. The two epimers of 1 were resolved through an acetonide reaction, and the absolute configurations of two derivatives were deduced by the analysis of their (13)C NMR differences induced by γ-gauche or steric effect. Based on it, the (13)C NMR assignment of 24R-1 and 24S-1 was also established.

Novel antiphytopathogenic compound 2-heptyl-5-hexylfuran-3-carboxylic acid, produced by newly isolated Pseudomonas sp. strain SJT25.

Pseudomonas sp. strain SJT25, which strongly antagonizes plant pathogens, was isolated from rice rhizosphere soil by a bioactivity-guided approach. A novel antiphytopathogenic compound was isolated from the fermentation broth of Pseudomonas sp.

Expression, purification, and characterization of a galactofuranosyltransferase involved in Mycobacterium tuberculosis arabinogalactan biosynthesis.

The major structural component of the cell wall of Mycobacterium tuberculosis is a lipidated polysaccharide, the mycoyl-arabinogalactan-peptidoglycan (mAGP) complex. This glycoconjugate plays a key role in the survival of the organism, and thus, enzymes involved in its biosynthesis have attracted attention as sites for drug action. At the core of the mAGP is a galactan composed of D-galactofuranose residues attached via alternating beta-(1-->5) and beta-(1-->6) linkages.

Carbohydrate recognition by Clostridium difficile toxin A.

Clostridium difficile TcdA is a large toxin that binds carbohydrates on intestinal epithelial cells. A 2-A resolution cocrystal structure reveals two molecules of alpha-Gal-(1,3)-beta-Gal-(1,4)-beta-GlcNAcO(CH(2))(8)CO(2)CH(3) binding in an extended conformation to TcdA. Residues forming key contacts with the trisaccharides are conserved in all seven putative binding sites in TcdA, suggesting a mode of multivalent binding that may be exploited for the rational design of novel therapeutics.

Synthesis of n-octyl 2,6-dideoxy-alpha-L-lyxo-hexopyranosyl-(1-->2)-3-amino-3-deoxy-beta-D-galactopyranoside, an analog of the H-disaccharide antigen.

The synthesis of an analog of the H-disaccharide antigen (2), in which the galactopyranosyl moiety bears an amino group at C-3 and the fucopyranosyl residue is deoxygenated at C-2, is reported. The key reaction in the preparation of 2 was the glycosylation of an appropriately protected n-octyl 3-azido-3-deoxy-galactopyranoside derivative with a 2,6-dideoxy thioglycoside promoted by 1-(phenylsulfinyl)piperidine and triflic anhydride. Disaccharide 2 is of interest in studies directed towards understanding the molecular basis of substrate recognition by the blood group A and B glycosyltransferases.

[Capillary electrophoretic enantioseparation of arylglycine amides with highly sulfated beta-cyclodextrin as chiral selector].

Enantiomers of nine arylglycine amides synthesized were successfully separated by capillary electrophoresis (CE) using highly sulfated beta-cyclodextrin (HS-beta-CD) as a chiral selector. Baseline enantioseparation of the analytes was obtained within 6 min at neutral pH but not the commonly used acidic condition. HS-beta-CD content, buffer type and concentration, and non-chiral additive were studied and optimized for high resolution and fast speed.

Nitrile biotransformations for highly efficient and enantioselective syntheses of electrophilic oxiranecarboxamides.

Catalyzed by a nitrile hydratase/amidase-containing microbial Rhodococcus sp. AJ270 whole-cell catalyst, a number of racemic trans-2,3-epoxy-3-arylpropanenitriles 1 underwent rapid and efficient hydrolysis under very mild conditions to afford 2R,3S-2-arylglycidamides 2 in excellent yield with enantiomeric excess higher than 99.5%.

Practical and convenient enzymatic synthesis of enantiopure alpha-amino acids and amides.

Catalyzed by the nitrile hydratase and the amidease in Rhodococcus sp. AJ270 cells under very mild conditions, a number of alpha-aryl- and alpha-alkyl-substituted DL-glycine nitriles 1 rapidly underwent a highly enantioselective hydrolysis to afford D-(-)-alpha-amino acid amides 2 and L-(+)-alpha-amino acids 3 in high yields with excellent enantiomeric excesses in most cases. The overall enantioselectivity of the biotransformations of nitriles originated from the combined effects of a high L-enantioselective amidase and a low enantioselective nitrile hydratase.