A Simple Synthesis of C-Glucosides Related to the Antitumor Agent Etoposide

Abstract

The synthesis of four new lignan derivatives 2a, 2b, 3a and 3b related to the anticancer agent etoposide has been accomplished. In these compounds a methylene or ethylene group of a C-glucoside separates the glucosidic moiety as present in etoposide (1) from its lignan aglycone bonded by an ethereal function. The key step in the synthesis involves the reaction of a benzylated alditol 4 or 5 and the unprotected 4′-demethylepipodophyllotoxin (6).     

An SPE Method for the Concurrent Extraction of Organochlorine and Phenoxy Acidic Pesticides in River Water

We present the validation of a multiresidue method for the concurrent SPE of organochlorine (OCP) and phenoxy-acidic pesticides (PA) in river water. The two classes of compounds show very different chemical characteristics. The analyses were performed by gas chromatography?Cmass spectrometry and by liquid chromatography?Celectrospray ionization?Cmass spectrometry. The method was validated at three different concentrations: method limit of quantitation, 0.5 and 5 ??g L^?1. The recoveries were in the range 65?C135% for all the target compounds and in the range 83?C113% with RSD <20% for most of them at all the concentrations tested. The method showed good accuracy, precision, and sensitivity, and allowed the analysis of the selected pesticides at a concentration lower than that required by the EU current legislation for surface water [1]. The single-step procedure reduced artifacts, matrix effects, and speeded up sample preparation.     

Complete (1)H and (13)C NMR spectral assignment of alpha- and beta-adenosine, 2'-deoxyadenosine and their acetate derivatives

(1)H and (13)C NMR chemical shifts of alpha- and beta-anomers of adenosine, 2'-deoxyadenosine and their acetate derivatives were completely and definitely assigned using the concerted application of one- and two-dimensional experiments (gCOSY, gNOESY, gHSQC and gHMBC). The influence of the stereochemistry of the purine base on the NMR data of the hydrogen and carbon atoms of the furanose moiety was estimated.     

Upper bounds of degree 3 for the probability of the union of events via linear programming

We consider the problem of generating upper bounds for the probability of the union of events when the individual probabilities of the events as well as the probabilities of pairs and triples of these events are known. By formulating the problem as a Linear Program, we can obtain bounds as objective function values corresponding to dual basic solutions. The upper bounds are based on underlying graph structures.     

Complete 1H and 13C NMR spectral assignment of 17-hydroxy epimeric sterols with planar A or A and B rings

Complete 1H and 13C spectral assignments of 17beta- and 17alpha-hydroxy epimers of three biologically active sterols (boldenone, 3-methoxyestradiol and 3-methoxydihydroequilenin) were achieved making use of one- and two-dimensional NMR techniques (1D-HOHAHA, DEPT, COSY, NOESY, TOCSY, HSQC and COLOC).     

Oligosaccharides Related to Tumor-Associate Antigens. Part 2. Conformational analysis of the trisaccharide α-L-Fucp-(1→2)-β-D-Galp-(1→3)-β-D-GalpNAc,epitope structure recognized by the MBr1 antibody

The conformational space of the trisaccharide α-L -Fuc-(1→2)-β- D -Gal-(1→3)-β -D -GalNAc-1-OPr ( 2 ) and of its component disaccharide moieties α -L -Fuc-(1→2)-β -D -Gal-1-OMe ( 3 ) and β -D -Gal-(1→3)-β- D -GalNAc-1-OPr ( 4 ) was investigated with the aid of molecular-mechanics energy minimizations and molecular-dynamics simulations. These calculations suggested the occurrence of two conformations for each compound characterized by different ? and Ψ glycosidic angles. However, ¹H-NMR investigation of D₂O solutions of 2–4 indicated a sure preference for one of the two conformers with a contribution of the other one ranging from negligible to low.     

Condensed Phase Membrane Introduction Mass Spectrometry with Direct Electron Ionization: On-line Measurement of PAHs in Complex Aqueous Samples

Polycyclic aromatic hydrocarbons (PAHs) are USEPA regulated priority pollutants. Their low aqueous solubility requires very sensitive analytical methods for their detection, typically involving preconcentration steps. Presented is the first demonstrated ‘proof of concept’ use of condensed phase membrane introduction mass spectrometry (CP-MIMS) coupled with direct liquid electron ionization (DEI) for the direct, on-line measurement of PAHs in aqueous samples. DEI is very well suited for the ionization of PAHs and other nonpolar compounds, and is not significantly influenced by the co-elution of matrix components. Linear calibration data for low ppb levels of aqueous naphthalene, anthracene, and pyrene is demonstrated, with measured detection limits of 4 ppb. Analytical response times (t_10%–90% signal rise) ranged from 2.8 min for naphthalene to 4.7 min for pyrene. Both intra- and interday reproducibility has been assessed (<3% and 5% RSD, respectively). Direct measurements of ppb level PAHs spiked in a variety of real, complex environmental sample matrices is examined, including natural waters, sea waters, and a hydrocarbon extraction production waste water sample. For these spiked, complex samples, direct PAH measurement by CP-MIMS-DEI yielded minimal signal suppression from sample matrix effects (81%–104%). We demonstrate the use of this analytical approach to directly monitor real-time changes in aqueous PAH concentrations with potential applications for continuous on-line monitoring strategies and binding/adsorption studies in heterogeneous samples.

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