Quantized vortices in the ideal bose gas: a physical realization of random polynomials

We propose a physical system allowing one to experimentally observe the distribution of the complex zeros of a random polynomial. We consider a degenerate, rotating, quasi-ideal atomic Bose gas prepared in the lowest Landau level. Thermal fluctuations provide the randomness of the bosonic field and of the locations of the vortex cores. These vortices can be mapped to zeros of random polynomials, and observed in the density profile of the gas.     

The Deoxygenation and Isomerization of Artemisinin and Artemether and Their Relevance to Antimalarial Action

The treatment of artemisinin ( 1 ) and β-artemether ( 6 ) with Zn dissolving in AcOH for a few hours results in mono-deoxygenation giving deoxyartemisinin ( 5 ) and deoxy-β-artemether ( 7 ), respectively, as the sole product. In contrast, submission of 1 to FeCl₂ · 4 H₂O in MeCN at room temperature for 15 min causes only isomerization, (3aS,4R,6aS,7R,10S,10aR)-octahydro-4,7-dimethyl-8-oxo-2H-10H-furo[3,2-i] benzopyran-10-yl acetate ( 8 ) and (3R)-3-hydroxydeoxyartemisinin ( 9 ) being produced in 78 and 17% yield, respectively. The action of FeCl₂ · 4 H₂O in MeCN on 6 is similar. Under the same conditions, 6 gives products analogous to 8 and 9 accompanied by an epimeric mixture of 2-[4-methyl-2-oxo-3-(3-oxobutyl)cyclohexyl]propanaldehyde in yields of 32, 23, and 16%, respectively. No epoxide is formed on repeating the last two experiments in the presence of cyclohexene. The deoxygenation of 1 and 6 by Zn is rationalized in terms of its oxophilic nature. The catalyzed isomerization of 1 and 6 by Fe²⁺ is attributed to the redox properties of the Fe²⁺/Fe³⁺ system.     

Tactics for the asymmetric preparation of 2-azabicyclo[3.1.0]hexane and 2-azabicyclo[4.1.0]heptane scaffolds

In this contribution, two methods are presented for the removal of benzyl-type protecting groups attached to the nitrogen atom of 2-azabicyclo[3.1.0]hexane and 2-azabicyclo[4.1.0]heptane systems. The first, based on the Polonovski reaction, is suitable for [3.1.0] systems. The second relies on an elimination process, starting from derivatives of O-methyl phenylglycinol, and is more general in terms of the substrates tolerated. Secondary bicyclic cyclopropylamines, including enantiomerically pure molecules, can thus be accessed. These compounds are then ready for further functionalisation.     

A bidirectional approach to the synthesis of polypropionates: synthesis of C1-C13 fragment of zincophorin and related isomers

The structure-activity study of a bioactive natural product containing polypropionate subunits requires that its stereoisomers also be evaluated. Therefore, a general approach to synthesize these motifs is necessary. We describe herein the synthesis of the C1-C13 polypropionate subunit of zincophorin and isomers thereof using a two-reaction sequence: an aldol reaction using a mixture of tetrasubstituted enoxysilanes and a hydrogen-transfer reaction, both under Lewis acid control. Selection of the appropriate Lewis acid dictates the stereochemical outcome of these reactions. From a tactical standpoint, this study shows how a polypropionate sequence can be read and constructed in two directions, either the east-west or the west-east approaches. The choice of the optimal route is influenced by the number of complexation sites that can interfere in the aldol step under bidentate Lewis acid control.     

Identification by LC-ESI-MS of flavonoids responsible for the antioxidant properties of Mallotus species from Vietnam

Several Mallotus species (Euphorbiaceae) are used in Vietnam as edible plants or as traditional medicines for different indications, some related to the treatment of inflammatory diseases. This study investigated the antioxidant activities of 33 samples from 17 Vietnamese Mallotus species. We also evaluated potential cytotoxic activity against human cervix carcinoma HeLa and human lung fibroblast WI-38 cells. Our aim is to develop safe dietary supplements with a protective effect against various diseases caused by tissue damage and the acceleration of the aging process linked to reactive oxygen species. These tests allowed the identification of non-cytotoxic plant species exhibiting significant antiradical properties. These antioxidant properties may be explained by their polyphenol composition. The antioxidant activity of the most active Mallotus species was further analyzed with and without tannins removal. We also identified by LC-ESI-MS some flavonoids responsible for a part of this activity.     

5-epi-Canadensene and other novel metabolites of Taxus canadensis

The Canadian yew distinguishes itself from other yews by the nature of its taxane metabolites. We are now reporting a new canadensene taxane whose stereochemistry is rigorously established. The three-dimensional structures of canadensene, 5-epi-canadensene and three other related bicyclic taxanes isolated from other yews were calculated using distance constraints derived from NMR data. The stereochemistry of the substituents, the polar acetate groups and the double bonds determine the 3D models. In addition, three new taxanes were also characterized and some biosynthetic speculations are presented.     

1‐Methoxyhexane‐3‐thiol,a Powerful Odorant of Clary Sage (Salvia sclarea L.)

The peculiar and highly diffusive odor signal of flowering clary‐sage plants (Salvia sclarea L.) was identified to derive from trace amounts of 1‐methoxyhexane‐3‐thiol ( 1 ) by mass‐spectrometry analysis and confirmed by comparison with synthetic racemic thiol (±)‐ 1 . The enantiomers (S)‐ and (R)‐ 1 were prepared by enantioselective synthesis, and the absolute configuration of (S)‐ 1 was fully corroborated by X‐ray‐diffraction analysis of the crystalline thioester (1′S,1S)‐ 2 . Compound (S)‐ 1 is one of the most powerful odorants known, with a detection threshold of 0.04⋅10⁻³ ng/l air, and is, with its herbaceous‐green, alliaceous, and perspiration profile, key to the fragrance of clary‐sage flowers and of the freshly distilled essential oil. As a consequence of its unique odor, 1 was also suspected to be part of the volatiles of a Ruta species where it was subsequently identified together with its homologue, 1‐methoxyheptane‐3‐thiol ( 3 ), 1‐methoxy‐4‐methylpentane‐3‐thiol ( 4 ), and the known 4‐methoxy‐2‐methylbutane‐2‐thiol ( 5 ). The syntheses of (±)‐ 3 and (±)‐ 4 as well as of the enantiomer (R)‐ 4 are described. In both natural fractions, the ratio (S)‐ 1 /(R)‐ 1 was slightly in favor of the (S)‐enantiomer. Natural 4 has (R)‐configuration.     

Selective Introduction of Sulfhydryl Groups into Recombinant Proteins for Study of Protein–Protein Interactions

In the present work, we proposed to create special sorbents for the study of protein–protein interactions, based on the fixation of cysteine-inserted beta-casein mutants with thiol-Sepharose resin. As a model system, we used bovine beta-casein, which belongs to the family of intrinsically unstructured proteins. Insertion of distal cysteines into the unfolded protein was not found to significantly change beta-casein properties. An amphiphilic beta-casein molecule has one hydrophilic domain and one hydrophobic domain placed on the N- and C-terminus, thus enabling one to exploit its capacity to engage in different types of intermolecular interactions. Two different casein-Sepharose sorbents incorporating either C-4 or C-208 beta-casein mutants bound to thiol-Sepharose were produced, exposing the hydrophobic domain in the case of the C-4 and the hydrophilic domain in the case of the C-208 mutant, respectively. The results obtained using the proposed sorbents with native beta-casein, another partially unfolded protein prion, and an oligomeric globular glyceraldehyde-3-phosphate dehydrogenase were found to be consistent with the data obtained by ELISA on free protein–protein complexes. Thus, Sepharose modified with various proteins is suitable for isolation of proteins interacting with the chromatographic phase bound partners from multicomponent systems such as milk. The obtained results allow the proposing of a fast and convenient method to be used for isolation of proteins, determination of protein-interacting partners, and the study of multi-protein complexes.     

Development and validation of an ion‐exchange chromatography method for heparin and its impurities in heparin products

An anion‐exchange liquid chromatography method for the determination of heparin and its impurities (dermatan sulfate and oversulfated chondroitin sulfate) was developed using chemometric‐assisted optimization, including multivariate experimental design and response surface methodology. The separation of heparin, dermatan sulfate, and oversulfated chondroitin sulfate (R_s above 2.0) was achieved on a Dionex RF IC IonPac AS22 column with a gradient elution of 10–70% of 2.5 M sodium chloride and 20 mM Tris phosphate buffer (pH 2.1) at a flow rate of 0.6 mL/min and UV detection at 215 nm. Method validation shows good linearity (r > 0.99), acceptable precision (%relative standard deviations <11.4%) and trueness (%recovery of 92.3–103.9%) for all analytes. The limits of detection for dermatan sulfate and oversulfated chondroitin sulfate are equivalent to 0.11% w/w (10.5 μg/mL) and 0.07% w/w (7.2 μg/mL), while the limits of quantification are 0.32% w/w (31.5 μg/mL) and 0.22% w/w (22.0 μg/mL) relative to heparin, respectively. The method is specific for heparin, dermatan sulfate, and oversulfated chondroitin sulfate without interference from mobile phase and sample matrices and could be used for accurate quantitation the drug and its impurities in a single run. Applications of the method reveal contents of heparin between 90.3 and 97.8%. Dermatan sulfate and oversulfated chondroitin sulfate were not detected in any of the real‐life samples.