Organocatalytic mannich-type reactions of trifluoroethyl thioesters

Direct organocatalytic Mannich-type reactions of thioesters provide for the expedient and diastereoselective synthesis of protected beta-amino acids. A variety of thioesters were found to be reactive with different imines under mild conditions to provide beta-amino acids in good yields. This chemistry was extended to a diastereo- and enantioselective variant.     

Plasma fingerprinting with GC-MS in acute coronary syndrome

New biomarkers of cardiovascular disease are needed to augment the information obtained from traditional indicators and to illuminate disease mechanisms. One of the approaches used in metabolomics/metabonomics for that purpose is metabolic fingerprinting aiming to profile large numbers of chemically diverse metabolites in an essentially nonselective way. In this study, gas chromatography-mass spectrometry was employed to evaluate the major metabolic changes in low molecular weight plasma metabolites of patients with acute coronary syndrome (n = 9) and with stable atherosclerosis (n = 10) vs healthy subjects without significant differences in age and sex (n = 10). Reproducible differences between cases and controls were obtained with pattern recognition techniques, and metabolites accounting for higher weight in the classification have been identified through their mass spectra. On this basis, it seems inherently plausible that even a simple metabolite profile might be able to offer improved clinical diagnosis and prognosis, but in addition, specific markers are being identified.     

Assembly of spirooxindole derivatives containing four consecutive stereocenters via organocatalytic Michael-Henry cascade reactions

A novel organocatalytic strategy for the synthesis of highly substituted spirocyclopentaneoxindoles was developed employing simple nitrostyrenes and 3-substituted oxindoles as starting materials. Michael-Henry cascade reactions, enabled through cinchona alkaloid organocatalysis, provided products in high yield and excellent enantioselectivity in a single step.     

Tandem column for the simultaneous determination of arginine, ibuprofen and related impurities by liquid chromatography

Ibuprofen arginate is a rapidly absorbed salt designed to promote more rapid onset of analgesia than commercially available forms of ibuprofen. Ibuprofen and arginine have very different polarities and this becomes in a chromatographic problem, further complicated with the determination of related compounds, which is necessary in stability assays of the pharmaceutical forms. The common solution is the employment of two separate methods, but this is time consuming. A LC method has been developed to determinate both compounds and related impurities in one run. Ibuprofen, arginine and three ibuprofen related impurities (B, E and J) have been baseline separated with isocratic conditions at pH 3.0 and run time under 20 min by employing a tandem combination of two different stationary phases: first a ZORBAX SB-C18 column from Agilent (250 mm x 4.6 mm and 5 microm) and downstream a SUPELCOSIL LC-NH2 column from Supelco (150 mm x 4.6 mm and 3 microm). The octadecyldiisobutylsilane column provides the separation of ibuprofen and its impurities by a hydrophobic mechanism, whereas aminopropyl column offers selective retention of arginine by dipolar interaction mechanism. Method has been successfully validated following ICH guidelines and it has been demonstrated to be reliable for arginine, ibuprofen and related impurities determination in sachets of two different dosages as pharmaceutical forms. Moreover, stress test has proved the selectivity of the method for degradation products, such as those that can emerge throughout long-term stability assays.     

Pipecolic acid-catalyzed direct asymmetric mannich reactions

[STRUCTURE: SEE TEXT] Mannich reactions between aldehydes and N-p-methoxyphenyl-protected alpha-imino ethyl glyoxylate have been performed using (S)-pipecolic acid as catalyst. The reactions give both syn- and anti-products (dr=1.4-2:1) with high enantioselectivities (>98% ee). In contrast, (S)-proline-catalyzed reactions give mainly syn-products with high enantioselectivities. Computational studies reveal that the energetic preference between the transition structures involving the s-cis-enamine and the s-trans-enamine is smaller for the pipecolic acid as compared to proline, yielding the (2S,3R)-anti and the (2S,3S)-syn Mannich product in nearly equal amounts.     

Metabolomic profiling of serum in the progression of Alzheimer's disease by capillary electrophoresis–mass spectrometry

There is high interest in the discovery of early diagnostic biomarkers of Alzheimer's disease, for which metabolomics exhibits a great potential. In this work, a metabolomic approach based on ultrafiltration and analysis by CE‐MS has been used to obtain representative fingerprints of polar metabolites from serum samples in order to distinguish between patients with Alzheimer's disease, mild cognitive impairment, and healthy controls. By the use of partial least squares discriminant analysis it was possible to classify patients according to the disease stage and then identify potential markers. Significant increase was observed with progression of disease in levels of choline, creatinine, asymmetric dimethyl‐arginine, homocysteine‐cysteine disulfide, phenylalanyl‐phenylalanine, and different medium chain acylcarnitines. On the other hand, asparagine, methionine, histidine, carnitine, acetyl‐spermidine, and C5‐carnitine were reduced in these serum samples. In this way, multiple essential pathways were found implicated in the underlying pathology, such as oxidative stress or defects in energy metabolism. However, the most interesting results are related to the association of several vascular risk factors with Alzheimer's disease.     

Application of new methodologies based on design of experiments, independent component analysis and design space for robust optimization in liquid chromatography

HPLC separations of an unknown sample mixture and a pharmaceutical formulation have been optimized using a recently developed chemometric methodology proposed by W. Dewé et al. in 2004 and improved by P. Lebrun et al. in 2008. This methodology is based on experimental designs which are used to model retention times of compounds of interest. Then, the prediction accuracy and the optimal separation robustness, including the uncertainty study, were evaluated. Finally, the design space (ICH Q8(R1) guideline) was computed as the probability for a criterion to lie in a selected range of acceptance. Furthermore, the chromatograms were automatically read. Peak detection and peak matching were carried out with a previously developed methodology using independent component analysis published by B. Debrus et al. in 2009. The present successful applications strengthen the high potential of these methodologies for the automated development of chromatographic methods.     

Metabolomic assessment with CE-MS of the nutraceutical effect of Cystoseira spp extracts in an animal model

There is a need of scientific evidence of claimed nutraceutical effects, but also there is a social movement towards the use of natural products and among them algae are seen as rich resources. Within this scenario, the development of methodology for rapid and reliable assessment of markers of efficiency and security of these extracts is necessary. The rat treated with streptozotocin has been proposed as the most appropriate model of systemic oxidative stress for studying antioxidant therapies. Cystoseira is a brown alga containing fucoxanthin and other carothenes whose pressure-assisted extracts were assayed to discover a possible beneficial effect on complications related to diabetes evolution in an acute but short-term model. Urine was selected as the sample and CE-TOF-MS as the analytical technique to obtain the fingerprints in a non-target metabolomic approach. Multivariate data analysis revealed a good clustering of the groups and permitted the putative assignment of compounds statistically significant in the classification. Interestingly a group of compounds associated to lysine glycation and cleavage from proteins was found to be increased in diabetic animals receiving vehicle as compared to control animals receiving vehicle (N6,N6,N6-trimethyl-L-lysine, N-methylnicotinamide, galactosylhydroxylysine, L-carnitine, N6-acetyl-N6-hydroxylysine, fructose-lysine, pipecolic acid, urocanic acid, amino-isobutanoate, formylisoglutamine. Fructoselysine significantly decreased after the treatment changing from a 24% increase to a 19% decrease. CE-MS fingerprinting of urine has provided a group of compounds different to those detected with other techniques and therefore proves the necessity of a cross-platform analysis to obtain a broad view of biological samples.     

Capillary electrophoresis for the determination of new markers of natural latex quality

Nowadays, increasing use of latex products in the healthcare area has also led to an increase in new scientific controls of raw material and manufactured products in order to maintain higher standards in quality control. Since field latex is a rich environment for microbial growth, in the absence of adequate preservation, the carbohydrates that it contains become microbiologically oxidised to the so-called volatile fatty acids (VFAs). Samples of natural rubber latex coming from different countries and processed in different ways have been tested by applying a capillary electrophoresis method for the measurement of the short-chain organic acids present in sera. The separation was performed with phosphate buffer at pH 6.25 and cetyltrimethylammonium bromide (CTAB) as background electrolyte in an uncoated fused-silica capillary with -10 kV of applied potential. The sample needs no other pre-treatment more than coagulation to obtain the serum. In the assayed samples, it has been shown that poorly-preserved latex presented higher amounts of succinic acid and lower amounts of malic acid. The succinic to malic acid ratio may be an important parameter because it cannot be altered by dilution or similar processes such as the traditional VFA index, used to determine the quality of latex. Ratios for succinic to malic acid <0.6 have been found for well-preserved latex and >0.6 for poorly-preserved latex.