22,-Dimethyl-4-phenyloxazoline and 2,2-dimethyl-4,5-diphenylimidazolidine as new chiral auxiliaries. Applications to asymmetric nitrile oxide cycloadditions

Asymmetric dipolar cycloadditions of a nitrile oxide to the acrylamide derivatives of two new chiral auxiliaries, (R)-2,2-dimethyl-4-phenyloxazolidines and (S,S)-2,2-dimethyl-4,5-diphenylimidazolidine, show satisfactorily high diastereoselectivities (up to 91%).     

Structural Effects of Oligosaccharide-Branched Cyclodextrins on the Dual Recognition toward Lectin and Drug

Bi-galactose-branched cyclodextrins (Bi-Gal-CDs)(1–6) having different spacer arm lengths between two terminal galactoses were foundto have the optimum length for association with PNA lectin. Also, the inclusioninteraction of the drug depended on the length of the spacer arms. The dual association of thesecompounds was quantitatively evaluated by SPR and compared to the other oligosaccharide-branchedCDs (Scheme 1). The number and the length of the spacer arm are important for theassociation both with the lectin and drug for the purpose of targeting drug-delivery systems.The association constants K of bi-Gal-CD (2) with rat liver cells showed a 60 timeshigher association than with PNA. Direct evidence of the association between PNA andbi-Gal-CD (2) was characterized by AFM observations. The results obtained strongly suggested a method to find a new design for the targeting drug carrier. In order toincrease the association with the cell, a sufficient spacer arm length is necessary for the effectivedual recognition of the oligosaccharide-CDs. In order to increase the inclusion of thedrug, the CD structure of a multi-saccharide branch is necessary.     

Synthesis and asymmetric polymerization of (S)‐N‐maleoyl‐L‐leucine propargyl ester

A kind of N‐substituted maleimide (RMI), chiral (S)‐N‐maleoyl‐L ‐leucine propargyl ester ((S)‐PLMI) with a specific rotation of [α]₄₃₅ = ?27.5° was successfully synthesized from maleic anhydride, L ‐leucine, and propargyl alcohol. (S)‐PLMI was polymerized by three polymerization methods to obtain the corresponding optically active polymers. Asymmetric anionic, radical, and transition‐metal‐catalyzed polymerizations were carried out using organometal/chiral ligands, 2,2′‐azobisisobutyronitrile (AIBN) and (bicyclo [2,2,1]hepta‐2,5‐diene) chloro rhodium (I) dimer ([Rh(nbd) Cl]₂), respectively. Poly((S)‐PLMI) obtained by [Rh(nbd)Cl]₂ in DMF showed the highest specific rotation of ?280.6°. Chiroptical properties and structures of the polymers obtained were investigated by GPC, CD, IR, and NMR measurements. Two types of poly((S)‐PLMI)‐bonded‐silica gels as the chiral stationary phase (CSP) were prepared for high‐performance liquid chromatography (HPLC). Their optical resolution abilities were also elucidated. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3722–3738, 2007     

Spin-singlet superconductivity and antiferromagnetic correlations for the field-aligned powder of the triangular lattice NaxCoO2 · yH2O

Nuclear magnetic resonance and relaxation measurements of the ⁵⁹Co nuclei for the well-defined field-aligned powder of the triangular lattice superconductor Na_xCoO₂ · yH₂O with a nearly optimal composition for the transition temperature T_c have been performed. Detailed analyses indicate that the Knight shifts for the directions parallel and perpendicular to the CoO₂ plane and the spin-lattice relaxation rates, taken by making an inevitable deterioration of specimen minimal, are significantly smaller than most of the data reported to date, and that this compound is classified into one of the unconventional spin-singlet superconductors as suggested by recent works for single crystals with a lower T_c. A small enhancement of two-dimensional antiferromagnetic spin correlations at some nonzero wave vector may emerge near T_c.     

Understanding the European policy landscape and its impact on change in mathematics and science pedagogies

Effecting an increase in the use of inquiry-based learning pedagogies in mathematics and science at a large scale across Europe has been promoted within the European education policy space. The primary goal is greater numbers of young people having more positive dispositions towards future careers in science, engineering and technology (Rocard in EUR22845—science education now: a renewed pedagogy for the future of Europe, http://www.eesc.europa.eu/resources/docs/rapportrocardfinal.pdf, 2007). We report on policy research as part of a European funded project that aims to support professional development that might bring about such changes. Our analysis points to policy activity that, to a greater or lesser degree, appears to be ineffective in meeting the desired outcomes in respect of teacher change. We identify why, although there is much policy activity, initiatives struggle to make an impact on teaching practices and learners’ experiences. Overall we point to misalignment in what policy defines in terms of input to learning, what is measured and valued in terms of outcomes, and what is desired in the teaching process. We also point to how policy fails to support development of the individual teacher and the teaching profession as a whole in ways that might effect the desired change.     

On distance two graphs of upper bound graphs

For a poset P=(X,≤), the upper bound graph (UB-graph) of P is the graph U=(X,E_U), where uv∈E_U if and only if u≠v and there exists m∈X such that u,v≤m. For a graph G, the distance two graph DS₂(G) is the graph with vertex set V(DS₂(G))=V(G) and u,v∈V(DS₂(G)) are adjacent if and only if d_G(u,v)=2. In this paper, we deal with distance two graphs of upper bound graphs. We obtain a characterization of distance two graphs of split upper bound graphs.     

Synthesis of two regiospecific isomers of monotosyl-γ-cyclodextrin

Tosylation of -cyclodextrin in an aqueous alkaline solution gave two regiospecific isomers (2-monotosyl--cyclodextrin(1) and 6-monotosyl--cyclodextrin(2)), that could recognize and catalyze small sized guest molecules; 2-monotosyl--CD recognized small sized guest molecules more effectively than did 6-monotosyl--CD.     

Asymmetric anionic polymerization of N‐1‐naphthylmaleimide with chiral ligand‐organometal complexes in toluene

Asymmetric anionic homopolymerizations of N‐1‐naphthylmaleimide (1‐NMI) were performed with chiral ligand/organometal complexes to form optically active polymers. Poly(1‐NMI)s obtained with methylene‐bridged bisoxazoline derivatives (Rbox)‐diethylzinc (Et₂Zn) complexes showed high specific optical rotations ([α]) from +152.3 to +191.4°. Circular dichroism spectra of the polymers exhibited a split Cotton effect in the UV absorption‐band region. According to the exciton chirality method, the absolute configuration of the polymer main chain was determined according to the following method: (+)‐poly[N‐substituted maleimides (RMI)] main chains can contain more (S,S)‐ than (R,R)‐configurations. (?)‐Poly(RMI) main chains can contain more (R,R)‐ than (S,S)‐configurations. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3556–3565, 2001     

Criticality in a model for thermal ignition in three or more dimensions

An explicitly resolvable model, which was instroduced in a previous paper (see [1]), is used to obtain exact behaviour of its bifurcation curves. The model closely approximates the true Arrhenius law for a spherical vessel of reacting material undergoing an exothermic reaction in three or more dimensions. For a sequence of values of a parameter, which is the reciprocal of the dimensionless activation energy, the number of the solutions changes for certain values of the eigenparameter Further, there exist solutions for all then is non-zero.

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Zusammenfassung Mit Hilfe eines explizit lösbaren Modells, das in einer früheren Arbeit eingeführt wurde (siehe [1]), erhält man das exakte Verhalten der zugehörigen Verzweigungskurven. Das Modell approximiert gut das Arrheniussche Gesetz für exotherme Reaktionen in einem sphärischen Topf in drei oder mehr Dimensionen. Für eine Folge von Werten des Parameters, welches als Reziproke der dimensionslosen Aktivierungsenergie dient, ändert sich die Anzahl der Lösungen zum Eigenwert, der durch gesteuert wird. Weiter gibt es für alle mindestens eine Lösung, sofern 0 gilt.

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Supported in part by the Deutsche Forschungsgemeinschaft and in part by the Victoria University of Wellington Fellowship Committee.