The hydrolysis of epoxides catalyzed by inorganic ammonium salts in water: kinetic evidence for hydrogen bond catalysis.

Naturally-occurring inorganic ammonium ions have been recently reported as efficient catalysts for some organic reactions in water, which contributes to the understanding of the chemistry in some natural environments (soils, seawater, atmospheric aerosols, …) and biological systems, and is also potentially interesting for green chemistry as many of their salts are cheap and non-toxic. In this work, the effect of NH4+ ions on the hydrolysis of small epoxides in water was studied kinetically. The presence of NH4+ increased the hydrolysis rate by a factor of 6 to 25 compared to pure water and these catalytic effects were shown not to result from other ions, counter-ions or from acid or base catalysis, general or specific. The small amounts of amino alcohols produced in the reactions were identified as the actual catalysts by obtaining a strong acceleration of the reactions when adding these compounds directly to the epoxides in water. Replacing the amino alcohols by other strong hydrogen-bond donors, such as trifluoroethanol (TFE) or hexafluoroisopropanol (HFIP) gave the same results, demonstrating that the kinetics of these reactions was driven by hydrogen-bond catalysis. Because of the presence of many hydrogen-bond donors in natural environments (for instance amines and hydroxy-containing compounds), hydrogen-bond catalysis is likely to contribute to many reaction rates in these environments.

Formation mechanisms and yields of small imidazoles from reactions of glyoxal with NH4(+) in water at neutral pH.

Imidazoles have numerous applications in pharmacology, chemistry, optics and electronics, making the development of their environmentally-friendly synthetic procedures worthwhile. In this work, the formation of imidazole, imidazole-2-carboxaldehyde, and 2,2-bis-1H-imidazole was investigated in the self-reaction of glyoxal and its cross-reactions with each of these compounds in aqueous solutions of inorganic ammonium salts at pH =7. Such conditions are relevant both as cheap and environmentally-friendly synthetic procedures and for the chemistry of natural environments where NH4(+) is abundant, such as in atmospheric aerosols. These reactions were investigated both by (1)H-NMR and UV-Vis absorption spectroscopy at room temperature with the objective to determine the formation pathways of the three imidazoles and the parameters affecting their yields, to identify the optimal conditions for their synthesis. The results show that only the simplest imidazole is produced by the self-reaction of glyoxal and that imidazole-2-carboxaldehyde and 2,2-bis-1H-imidazole are produced by cross-reactions of glyoxal with imidazole and imidazole-2-carboxaldehyde, respectively. The yields of imidazole-2-carboxaldehyde and 2,2-bis-1H-imidazole formed by the cross-reactions were close to unity, but the yield of imidazole formed by the self-reaction of glyoxal, YIm, was small and varied inversely with the initial glyoxal concentration, [G]0: YIm > 10% only for [G]0 < 0.1 M. The latter result was attributed to the kinetic competition between the imidazole-forming condensation pathway and the acetal/oligomer formation pathway of the glyoxal self-reaction and constitutes a bottleneck for the formation of higher imidazoles. Other parameters such as pH and the NH4(+) concentration did not affect the yields. Thus, by maintaining small glyoxal concentrations, high imidazole yields can be achieved in environmentally-friendly aqueous ammonium solutions at neutral pH. Under the same conditions, higher yields are expected expected from substituted carbonyl compounds, regardless of their concentration, as they produce less acetals.

Full characterization of PDX, a neuroprotectin/protectin D1 isomer, which inhibits blood platelet aggregation.

Our study aimed to establish the complete structure of the main dihydroxy conjugated triene issued from the lipoxygenation (soybean enzyme) of docosahexaenoic acid, named PDX, an isomer of protectin/neuroprotectin D1 (PD1/NPD1) described by Bazan and Serhan. NMR approaches and other chemical characterization (e.g. GC-MS, HPLC and LC-MS/MS) indicated that PDX is 10(S),17(S)-dihydroxy-docosahexa-4Z,7Z,11E,13Z,15E,19Z-enoic acid. The use of (18)O(2) and mass spectrometry showed that PDX is a double lipoxygenation product. Its structure differs from PD1, with E,Z,E geometry (PDX) instead of E,E,Z (PD1) and S configuration at carbon 10 instead of R. PDX inhibits human blood platelet aggregation at sub-micromolar concentrations.

In vitro anti-Helicobacter pylori activity of the probiotic strain Bacillus subtilis 3 is due to secretion of antibiotics.

A limited number of antibiotics can be used against Helicobacter pylori infection, and resistance jeopardizes the success of treatment. Therefore, a search for new agents is warranted. The use of probiotics to enhance gastrointestinal health has been proposed for many years, but the scientific basis of the prophylactic and therapeutic actions of probiotics has not yet been clearly delineated. Probiotic strain Bacillus subtilis 3, whose safety has previously been demonstrated, is known to have antagonistic properties against species of the family Enterobacteriaceae. In the present study, it was also found to inhibit H. pylori. The anti-H. pylori activity present in the cell-free supernatant was not related to pH or organic acid concentration. It was heat stable and protease insensitive. At least two antibiotics, detected by thin-layer chromatography (R(f) values, 0.47 and 0.85, respectively) and confirmed by high-performance liquid chromatographic analysis, were found to be responsible for this anti-H. pylori activity. All H. pylori strains tested were sensitive to both compounds. One of these compounds was identified as amicoumacin A, an antibiotic with anti-inflammatory properties. MICs for H. pylori determined in solid and liquid media ranged between 1.7 and 6.8 microg/ml and 0.75 and 2.5 microg/ml, respectively. The underestimation of MICs determined in solid medium may be due to physicochemical instability of the antibiotic under these test conditions. An additive effect between amicoumacin A and the nonamicoumacin antibiotic against H. pylori was demonstrated.

Three new flavonol malonylrhamnosides from Ribes alpinum.

Three new flavonol malonylrhamnosides, 3-O-(4"-O-malonyl)-alpha-L-rhamnopyranosides of mearnsetin, myricetin and quercetin respectively, together with the corresponding mearnsitrin, myricitrin, quercitrin and the 4-O-methyl phloracetophenone 2-O-beta-D-glucopyranoside, were isolated from the leaves of Ribes alpinum and fully characterized by spectrocopic methods including 2D NMR.

Two new glycosides from Astragalus caprinus.

A new glycoside of flavonol (1) and a new glycoside of a cycloartane-type triterpene (2) were isolated from the leaves and the roots of Astragalus caprinus, respectively. Their structures were elucidated in turn by spectroscopic data interpretation as 3-O-[[beta-D-xylopyranosyl(1-->3)-alpha-L-rhamnopyranosyl(1-->6)][beta-D-apiofuranosyl(1-->2)]]-beta-D-galactopyranosyl kaempferol (1) and 3-O-(beta-D-xylopyranosyl)-24-O-(beta-D-glucopyranosyl)-20,25-epoxycycloartane-3beta,6alpha,16beta,24alpha-tetrol (2).

Phenylpropanoids from Umbilicus pendulinus.

Phytochemical investigation of the leaves of Umbilicus pendulinus afforded in addition to 2-O-caffeoyl malate, isoquercitrin and Z-venusol, the new isomer E-venusol. Special NMR experiments were carried out to elucidate the configuration of the two latter compounds.

Synthesis of (5-azido-2-nitrobenzoyl)amido, (4-azido-2-nitrophenyl)amino, and (5-azido-2-nitro-3,4, 6-trifluorophenyl)amino derivatives of 17alpha-methylamino-, 17alpha-ethylamino-, and 17alpha-propylamino-5alpha-dihydrotestosterone as reagents of different linker lengths for the photoaffinity labeling of sex hormone binding globulins and androgen receptors.

The photoactivable aryl azide reagents, N-(5-azido-2-nitrobenzoyl)oxysuccinimide, 4-azido-1-fluoro-2-nitrobenzene, and 4-azido-1-nitro-2,4,5, 6-tetrafluorobenzene have been condensed at the extremity of three 17alpha-aminomethyl, 17alpha-aminoethyl, and 17alpha-aminopropyl side-chains introduced on (17S)-spiro-(3, 3-dimethoxy)-5alpha-androstan-17beta,2'-oxirane either directly, by ammonolysis, in the first case, or by conversion to nitrile intermediates with cyano or cyanomethyl anions and subsequent reduction to amines with lithium aluminum hydride, in the two other cases. The 3,3-dimethoxy group of these photoreagents was cleaved by acidolysis to a 3-ketone, which was reduced with sodium borohydride to a 3beta-alcohol. All of these compounds were characterized by (1)H- and (13)C-NMR as well as by (1)H, (13)C heteronuclear 2D NMR, which helped to resolve ambiguous assignments. Significant differences of substituent-induced effects on (13)C NMR signals were observed according to the 17alpha-side-chain length, the structure of the terminal aryl azide groups, and the solvent, showing a different behavior of N-5-azido-2-nitrobenzoyl derivatives as compared with 4-azido-2-nitrophenylamino and 5-azido-2-nitro-3,4, 6-trifluorophenylamino derivatives. The N-5-azido-2-nitrobenzoyl conjugates of the three 17alpha-aminomethyl, aminoethyl, and aminopropyl derivatives of 5alpha-dihydrotestosterone were tested as ligands for purified human sex hormone-binding globulin and for the cytosolic androgen receptor of rat ventral prostate by competition experiments with tritiated 5alpha-dihydrotestosterone. The increasing lengths of the aminomethyl, aminoethyl, and aminopropyl spacer arms of N-5-azido-2-nitrobenzoyl conjugates were found to correspond to decreasing relative binding affinities for sex hormone-binding globulin (0.76, 0.47, and 0.10, respectively, versus 1.00 for 5alpha-dihydrotestosterone) while only the longer aminoethyl and aminopropyl conjugates interacted significantly with the androgen receptors (0.05 and 0.10, respectively).

Identification and synthesis of a trisaccharide produced from lactose by transgalactosylation.

Enzymatic transgalactosylation of lactose by means of Streptococcus thermophilus, subspecies DN-001065, led to a mixture of D-galactose (approximately 4%), D-glucose (approximately 15%), lactose (approximately 51%), minor disaccharides (6%), trisaccharides (approximately 20%) and tetrasaccharides (3%). The major trisaccharide (approximately 16%) was identified by NMR spectroscopy and chemical synthesis as being the known beta-D-galactopyranosyl-(1-->3)-beta-D-galactopyranosyl-(1-->4)-D-glucos e (3'-beta-D-galactopyranosyl-lactose). It was purified from a mixture of peracetylated oligosaccharides by column chromatography followed by deacetylation. For the first time, 3'-beta-D-galactopyranosyl-lactose has been obtained on the 1 g scale, by resorting to simple techniques and equipment. NMR spectra have been unambiguously assigned.

"Cyclamen Red" colors based on a macrocyclic anthocyanin in carnation flowers.

The "cyclamen" red (or pink) colors in carnation flowers-cultivars Red Rox and eight others-are based on the presence of a new macrocyclic anthocyanin, pelargonidin 3,5-di-O-beta-glucoside(6' ', 6' "-malyl diester) identified by spectroscopic methods. The instability of the bridging malyl group with sugars in acidic medium readily causes the formation of the opened ring form, 3-O-(6' '-O-malylglucoside)-5-O-glucoside. The issue of cyclamen colors based in carnations on this original acylated pelargonidin derivative simulating those based on simpler cyanidin glycosides in Rosa cultivars is discussed using CIELAB colorimetric coordinates.

Selective protections on 2-allyloxycarbonylamino-1,6-anhydro-2-deoxy-beta-D-glucopyranose.

Regioselective monoacetylation of 2-allyloxycarbonylamino-1,6-anhydro-2-deoxy-beta-D-glucopyranose (1) gave a mixture of 3-O-acetyl and 4-O-acetyl derivatives, the structures of which were established by two-dimensional, phase-sensitive NOESY and confirmed by chemical proofs. The benzylation of 1, on the other hand, led to 2-allyloxycarbonylamino-1,6-anhydro-3,4-di- (5) or 2-allyloxycarbonylamino-1,6-anhydro-2-N-benzyl-3,4-di-O-benzyl-2-d eoxy-beta-D- glucopyranose (10). The regioselective cleavage of 5 with titanium tetrachloride gave the expected 3-O-benzyl derivative, the structure of which was ascertained by chemical proofs; the same reaction performed on 10 led to the opening of the anhydro ring to afford 3-benzyl-[3,4-di-O-benzyl-1,2-dideoxy-alpha-D-glucopyrano]-[2,1-d] -2- oxazolidone.

[Modifications, due to nutrition, of methyl and methylene 1H NMR signals in human plasma and normal serum samples]. / Etude des modifications apportées par la nutrition sur les signaux de RMN 1H méthyliques et méthyléniques d'échantillons de plasmas et sérums humains normaux.

The line width test has been realised on twelve normal healthy persons (seven men and five women). Blood was collected at different time during one day. The results obtained when blood samples was taking after eating, showed an appreciable decrease in the average methylene and methyl line width. The same test realised on clear serum samples added up with increasing quantities of triglycerids rich lipoproteins leads to the same result.