An attempt to distinguish between the components of a mixture of isomeric fragment ions

The [C₇H₁₀NO₃]⁺ ion in the normal mass spectrum of 2-ethoxycarbonyl-5-oxo-2-pyrrolidinepropanoic acid was shown to correspond to a mixture of two isomeric structures. By decreasing the ionizing electron energy, the one containing a CH₂CH₂COOH group becomes dominant. The proportion of the concentrations of the two isomeric ions was calculated by comparing their daughter ion spectra (obtained by linked scan at constant B/E) with the analogous spectra of a derivative partially labelled by deuterium at the carboxyl and amide groups.     

Highly enantioselective synthesis of 2-furanyl-hydroxyacetates from furans via the Friedel-Crafts reaction

The Friedel-Crafts reaction of alkyl glyoxylates with variously substituted furans was found to be efficiently catalyzed under simple, undemanding conditions by a 6,6'-dibromo-BINOL/Ti(IV) complex with high enantioselectivity. The reaction afforded chiral substituted 2-furanyl-hydroxyacetic acid esters, compounds of high synthetic interest, in good yield and enantiomeric excess, in most examples in the range of 90-97%.     

Estrogen-induced cholestasis results in a dramatic increase of b-series gangliosides in the rat liver

Hepatic ganglioside composition was investigated in normal and cholestatic Wistar rats. Cholestasis was induced by 17alpha-ethinylestradiol (EE; 5 mg/kg body weight s.c. for 18 days). As compared with controls, the EE administration resulted in severe cholestasis, as indicated by biochemical as well as morphological signs. Gangliosides isolated from the liver tissue were separated by TLC, with resorcinol-HCl detection and densitometric evaluation. As compared with controls, the total hepatic lipid sialic acid content in cholestatic rats was increased almost 2-fold (44.3 +/- 15.2 vs 79.1 +/- 9.0 nmol/g wet weight of liver tissue, p < 0.01). This increase was primarily due to the increase of ganglioside GD1a (3.6 +/- 1.0 vs 11.8 +/- 3.0 nmol/g wet weight of liver tissue, p = 0.001), as well as to the enormous up-regulation of b-series gangliosides GD3 (0.08 +/- 0.03 vs 2.0 +/- 1.2 nmol/g wet weight of liver tissue, p = 0.002), GD1b (0.1 +/- 0.06 vs 5.4 +/- 1.6 nmol/g wet weight of liver tissue, p = 0.002) and GT1b (0.06 +/- 0.03 vs 6.4 +/- 2.6 nmol/g wet weight of liver tissue, p = 0.002). As the majority of gangliosides are concentrated in cell membranes, our findings suggest that dramatic increase of b-series gangliosides might contribute to the protection of hepatocytes against the deleterious effects of cholestasis.     

Heat extraction of corn fiber hemicellulose

Water-soluble hemicellulose was extracted from corn fiber with microwave-assisted heat treatment. The effects of treatment temperature and initial pH of the aqueous extraction media were investigated regarding hemicellulose recovery and molecular mass of the isolated polysaccharides. In treatments carried out at neutral pH (simple water extraction), it has been demonstrated that hemicellulose recovery could be increased by applying higher treatment temperatures. However, the molecular weight of isolated hemicellulose gets significantly lower. For example, 10% of the raw materials' xylan was extracted at 160 degrees C and about 30% recovery was reached at 210 degrees C. However, the molecular mass of the isolated polysaccharide at 210 degrees C (5.82 x 10(4)) was about half of that measured at 160 degrees C (1.37 x 10(5)). Reducing the pH with sulfuric acid resulted in shorter polymer chains (1.7 x 10(4)) and lower hemicellulose yields (2.2%). Application of sodium hydroxide in the treatment showed that, compared with acid, considerably higher yields (11%) with longer polysaccharide chains (1.3 x 10(5)) could be obtained.     

Thermoascus aurantiacus CBHI/Cel7A production in Trichoderma reesei on alternative carbon sources

To develop functional enzymes in cellulose hydrolysis at or above 70 degrees C the cellobiohydrolase (CBHI/Cel7A) of Thermoascus aurantiacus was cloned and expressed in Trichoderma reesei Rut-C30 under the strong cbh1 promoter. Cellulase production of the parental strain and the novel strain (RF6026) was examined in submerged fermentation experiments using various carbon sources, which were lactose, Solka Floc 200 cellulose powder, and steam pretreated corn stover. An industrially feasible production medium was used containing only distiller's spent grain, KH(2)PO(4), and (NH(4))(2)SO(4). Enzyme production was followed by measurements of protein concentration, total cellulase enzyme activity (filter paper activity), beta-glucosidase activity, CBHI activity, and endogenase I (EGI) activity. The Thermoascus CBHI/Cel7A activity was taken as an indication of the heterologous gene expression under the cbh1 promoter.     

Enantioselective Friedel-Crafts reaction of acylpyrroles with glyoxylates catalyzed by BINOL-Ti(IV) complexes

We report the first efficient enantioselective Friedel-Crafts hydroxyalkylation of pyrroles having one electron-withdrawing group at the α, β or N-positions with alkyl glyoxylates catalyzed by readily available chiral BINOL-Ti(IV) complexes (1-5 mol %). The reaction regioselectively led to the desired pyrrole-hydroxyacetic acid derivatives with good yields (70-96%) and enantiomeric excesses up to 96%, and is applicable in multigram scale with low loading of the catalyst (1 mol %).     

Multiple beneficial effects of resveratrol and their chemical-biochemical basis

On the basis of in vitro and in vivo investigations trans-resveratrol (RV) is a natural, concentration-dependent formaldehyde (HCHO) mobilizer, scavenger, capture and carrier molecule. The capturing and mobilization of HCHO from a given biological unit (e.g. tissue) with RV (first step) generates a chemopreventive effect. The reaction products between endogenous HCHO and RV (second step) may exert killing/inhibiting effects on pathogens and/or cancer cells. These two steps result in the double effect of RV. From the model reaction mixture of RV and HCHO in diluted formalin solution, different reaction products were detected, separated and identified. Similar reactions can be observed between RV and endogenous HCHO in plant and animal tissues as well. Capturing the HCHO molecules in model experiments with HCHO-capture molecules (in vitro conditions) the antibacterial activity of RV decreased substantially. The in vitro investigations were extended to in vivo conditions. The discovery of a quadruple immune response of plants to pathogens resulting from pretreatment with RV opens new horizons in the confirmation of the diverse beneficial effects of RV.     

BINOL-based azacrown ether catalyzed enantioselective Michael addition: asymmetric synthesis of α-aminophosphonates

Several novel 1,1′-bi-2-naphthyl-appended azacrown ethers with donor side-arms were synthesized and applied for the first time as chiral catalysts in the asymmetric Michael addition of an N-protected aminomethylenephosphonate onto acrylonitriles, resulting in high diastereoselectivity and enantioselectivity. The absolute configuration of the adduct was determined from its experimental and calculated CD spectra.