Dereplicative Combination of HPLC/DAD/MS and 2D NMR to Identify Lichexanthone Isomers in Lichen Extracts.

Isomerically pure chlorobiphenyl congeners and hepatic function in the rat: Influence of position and degree of chlorination

Multiple dual-mode centrifugal partition chromatography as an efficient method for the purification of a mycosporine from a crude methanolic extract of Lichina pygmaea

Six pentacyclic triterpenoids, 3beta-stearyloxy-urs-12-ene (1), friedelin (2), 3beta-friedelinol (3), alpha-amyrin (4), beta-amyrin (5), and lupeol (6), have been isolated from the hexane extract of Maytenus salicifolia Reissek (Celastraceae) leaves. The molecular and structural formula as well as the stereochemistry of a new pentacyclic triterpene (1) were determined using data obtained from 1H and 13C NMR spectra, DEPT135 and by 2D HSQC, HMBC, COSY and NOESY experiments. The molecular formula C48H84O2 was established using quantitative 13C NMR, and the molecular weight (692 Da) was confirmed by elemental analysis and mass spectrometry (GC-MS).

The sequence information available for homeodomains reveals that salt bridges connecting pairs 19/30, 31/42, and 17/52 are frequent, whereas aliphatic residues at these sites are rare and mainly restricted to proteins from homeotherms. We have analyzed the influence of salt and hydrophobic bridges at these sites on the stability and DNA binding properties of human Hesx-1 homeodomain. Regarding the protein stability, our analysis shows that hydrophobic side chains are clearly preferred at positions 19/30 and 31/42. This stabilizing influence results from the more favorable packing of the aliphatic side chains with the protein core, as illustrated by the three-dimensional solution structure of a thermostable variant, herein reported. In contrast only polar side chains seem to be tolerated at positions 17/52. Interestingly, despite the significant influence of pairs 19/30 and 31/42 on the stability of the homeodomain, their effect on DNA binding ranges from modest to negligible. The observed lack of correlation between binding strength and conformational stability in the analyzed variants suggests that salt/hydrophobic bridges at these specific positions might have been employed by evolution to independently modulate both properties.

Three new 8-hydroxybriaranes—fragilides R–T (1–3) were obtained from a sea whip gorgonian coral Junceella fragilis. The structures of briaranes 1–3 were elucidated by using spectroscopic methods, including 1D (1H and 13C NMR), 2D (COSY, HSQC, HMBC, and NOESY experiments) NMR studies, and (+)-HRESIMS. Fragilides S and T (2 and 3) are the only briaranes known to possess 8α-hydroxy and 17β-methyl groups, respectively. Briarane 2 exerted an inhibition effect on iNOS release from RAW264.7; a macrophage cell line that originated from a mouse monocyte macrophage, stimulated with lipopolysaccharides.

The reaction of butyltin hydroxide oxide, BuSnO(OH), with p-toluenesulfonic acid, 4-CH3C6H4SO3H, yields the butyltin oxo cluster {(BuSn)12(μ3-O)14(μ2-OH)6}2+ mixed with a soluble ill-defined butylt...

The solution structure of the catalytic fragment of human fibroblast collagenase (MMP-1) complexed with a sulfonamide derivative of a hydroxamic acid compound (CGS-27023A) has been determined using two-dimensional and three-dimensional heteronuclear NMR spectroscopy. The solution structure of the complex was calculated by means of hybrid distance geometry-simulated annealing using a combination of experimental NMR restraints obtained from the previous refinement of the inhibitor-free MMP-1 (1) and recent restraints for the MMP-1:CGS-27023A complex. The hydroxamic acid moiety of CGS-27023A was found to chelate to the "right" of the catalytic zinc where the p-methoxyphenyl sits in the S1' active-site pocket, the isopropyl group is in contact with H83 and N80, and the pyridine ring is solvent exposed. The sulfonyl oxygens are in hydrogen-bonding distance to the backbone NHs of L81 and A82. This is similar to the conformation determined by NMR of the inhibitor bound to stromelysin (2, 3). A total of 48 distance restraints were observed between MMP-1 and CGS-27023A from 3D 13C-edited/12C-filtered NOESY and 3D 15N-edited NOESY experiments. An additional 18 intramolecular restraints were observed for CGS-27023A from a 2D 12C-filtered NOESY experiment. A minimal set of NMR experiments in combination with the free MMP-1 assignments were used to assign the MMP-1 (1)H, 13C, and 15N resonances in the MMP-1:CGS-27023A complex. The assignments of CGS-27023A in the complex were obtained from 2D 12C-filtered NOESY and 2D 12C-filtered TOCSY experiments.

Solution structure of sialyl Lewis X mimics studied by two-dimensional NMR

A pair of sesquiterpene glucosides, 3-hydroxysolavetivone-β-d-glucoside A (1) and 3-hydroxysolavetivone-β-d-glucoside B (2), have been isolated from the leaves of Nicotiana tabacum. The former is a new compound, while the latter is a known one. Their structures were established by spectroscopic methods including 1H, 13C, and 2D NMR. The relative configuration of C-3 in compound 2 was revised by NOESY experiment.

The structure of the O-specific polysaccharide from marine bacterium Litorimonas taeanensis G5T containing 2-acetamido-4-((3S,5S)-3,5-dihydroxyhexanamido)-2,4-dideoxy-d-quinovose and 2-acetamido-2,6-dideoxy-l-xylo-hexos-4-ulose

Phytochemical investigation of the whole plant of Achillea millefolium led to the isolation of three new sesquiterpenes which were trivially named as sesquiterpene lactone-esters A and B (1 and 2), and sesquiterpene lactone-diol (3). The structures of these compounds were determined with the help of one- and two-dimensional (1D and 2D) NMR techniques including 1H NMR, 13C NMR, HMQC, HMBC, COSY, and NOESY experiments.

Compounds 1-7 form a novel group of dithiocarbamates, first synthesized from the reaction of a series of primary amines with carbon disulfide and 3-bromo ethyl pyruvate in the presence of anhydrous potassium phosphate. Structure elucidation of this group of compounds was accomplished using extensive 1D and 2D NMR spectroscopic studies, including (1)H, (13)C, COSY, NOESY, HSQC, and gHMBC experiments. The distinction between the linear structures I, II and the cyclic structure III was made mainly on the basis of the analysis of the cross peak between H-2 and H-4a in the COSY spectra, in combination with the long-range correlation between H-2 and C-4, 6 in the gHMBC spectra.

The bphA, -B, -C, and -D genes from Pseudomonas testosteroni B-356 were mapped to a 5.5-kb DNA fragment of cloned plasmids pDA1 and pDA2 by use of deletion and insertion mutants of these plasmids. The expression of each of these genes was evaluated in Escherichia coli and in Pseudomonas putida, and it was found that the bphC and bphD genes are well expressed in both E. coli and P. putida cells while the bphA and bphB genes are very poorly expressed in E. coli, even when placed downstream of a tac promotor. P. putida clones carrying the bphA gene were used to study the metabolites produced from 4,4'-dichlorobiphenyl, 2,2'-dichlorobiphenyl, and 2,4'-dichlorobiphenyl. It was shown that dehalogenation of 4-Cl and 2-Cl occurs in the course of the initial oxygenase attack on these molecules, which always occurs on carbons 2 and 3, independently of the positions of the chlorine atoms. Our data also suggest that in the case of polychlorobiphenyl congeners carrying chlorine atoms on both rings, it appears that, depending on the chlorine positions, dioxygenation will occur predominantly on one ring over the other. However, attack of the more resistant ring is not excluded, resulting in multiple conversion pathways.

Chloro-7 H -benz[ de ]anthr-7-ones (chlorobenzanthrones) are useful as starting materials for synthesis of larger polycyclic aromatic compounds by means of condensation. In the synthesis, the position of the chlorine atom is very important because the structure of condensation products strongly depends on it. For this reason, we have synthesized several chlorobenzanthrones. Although 3- and 4-chlorobenzanthrone were prepared by direct chlorination of benzanthrone and by glycerol condensation of 2-chloroanthraquinone, respectively, the synthesis of 1- and 2-chlorobenzanthrone has not yet been successful. In the present study, we attempted to synthesize them by use of the Sandmeyer reaction. First, we nitrated benzanthrone with nitric acid; 1- and 2-nitrobenzanthrone were obtained by nitration in nitrobenzene at 50-60° and in glacial acetic acid at 105-110°, respectively. Then the nitroderivatives were reduced to corresponding aminoderivatives; the reduction was performed with sodium sulfide for 1-nitrobenzanthrone and with hydrogen chloride and tin for 2-nitrobenzanthrone. Finally, chlorination was carried out by use of the Sandmeyer reaction. The products were separated and purified by column-chromatography. The position of chlorination was confirmed by NMR spectroscopy.

Chloro-7 H -benz[ de ]anthr-7-ones (chlorobenzanthrones) are useful as starting materials for synthesis of larger polycyclic aromatic compounds by means of condensation. In the synthesis, the position of the chlorine atom is very important because the structure of condensation products strongly depends on it. For this reason, we have synthesized several chlorobenzanthrones. Although 3- and 4-chlorobenzanthrone were prepared by direct chlorination of benzanthrone and by glycerol condensation of 2-chloroanthraquinone, respectively, the synthesis of 1- and 2-chlorobenzanthrone has not yet been successful. In the present study, we attempted to synthesize them by use of the Sandmeyer reaction. First, we nitrated benzanthrone with nitric acid; 1- and 2-nitrobenzanthrone were obtained by nitration in nitrobenzene at 50-60° and in glacial acetic acid at 105-110°, respectively. Then the nitroderivatives were reduced to corresponding aminoderivatives; the reduction was performed with sodium sulfide for 1-nitrobenzanthrone and with hydrogen chloride and tin for 2-nitrobenzanthrone. Finally, chlorination was carried out by use of the Sandmeyer reaction. The products were separated and purified by column-chromatography. The position of chlorination was confirmed by NMR spectroscopy.