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.     

Application of tetraoxadiaza-crown ether derivatives as chiral selector modifiers in capillary electrophoresis

Two new diaza-crown ether derivatives (R-1, RS-1) have been synthesized from 1,4,10,13-tetraoxa-7,16-diazacyclooctadecane and tested as potential chiral selectors in capillary electrophoresis (CE) for the chiral separation of five amino acid derivatives. The individual use of the selectors did not lead to chiral differentiation. However, they enhanced the enantioselective effect of different cyclodextrins in dual selector systems. In this paper, we report the effect of different substituted diaza-crown ether derivatives on the separation results obtained in dual systems with cyclodextrins.     

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.     

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.     

Covalent attachment of poly(ethyleneglycol) to peptides and proteins

Carbonylimidazol-l-yl-mPEG is obtained quantitatively by reacting methoxypoly(ethyleneglycol) (mPEG) with 1.1 Eq of N,N′-carbonyldiimidazole in the presence of a stoechiometric amount of 4-dimethyl-aminopyridine used as hypernucleophilic acylation catalyst. Carbonylimidazol-l-yl-mPEG is quite stable in aqueous solutions with half-lives up to 70 h in pHs ranging from 6.0 to 7.0 at 25‡C. From reactivity studies toward amines with various nucleophilic strengths, it is suggested that carbonylimidazol-l-yl-mPEG may be best used to modify α-amino terminal function of proteins selectively or to introduce amino function on PEG chains.     

Synthesis,kinetic study,and application of Ti[O(CH2)4OCHCH2]4 in ring‐opening polymerization of ε‐caprolactone and radical polymerization

Ti[O(CH₂)₄OCH?CH₂]₄, used for the ring‐opening polymerization (ROP) of ε‐caprolactone, was synthesized through the ester‐exchange reaction of titanium n‐propoxide and 1,4‐butanediol vinyl ether, and its chemical structure was confirmed by nuclear magnetic resonance (¹H NMR) and thermogravimetric analysis (TGA). The mechanism and kinetics of Ti[O(CH₂)₄OCH?CH₂]₄‐initiated bulk polymerization of ε‐caprolactone were investigated. The results demonstrate that Ti[O (CH₂)₄OCH?CH₂]₄‐initiated polymerization of ε‐caprolactone proceeds through the coordination‐insertion mechanism, and all the four alkoxide arms in Ti[O (CH₂)₄OCH?CH₂]₄ share a similar activity in initiating ROP of ε‐caprolactone. The polymerization process can be well predicted by the obtained kinetic parameters, and the activation energy is 106 KJ/mol. Then, the rheological method was employed to investigate the feasibility of producing the crosslinked poly(ε‐caprolactone)‐poly (n‐butyl acrylate) network by using Ti[O(CH₂)₄OCH?CH₂]₄ as the ROP initiator. The tensile test demonstrates that the in situ generated crosslinked PCL‐PBA network in PMMA matrix provides the possibility of ameliorating the tensile properties of PMMA. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7773–7784, 2008     

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.