Synthesis of all of the four possible stereoisomers of pestalotin,a gibberellin synergist isolated from pestalotia cryptomeriaecola sawada

(-)-Pestalotin [(6S, l'S)-6-(1'-hydroxypentyl)-4-methoxy-5,6-d dihydro-2-pyrone 1a]and its three other stereoisomers were synthesized either by utilizing the Sharpless asymmetric epoxidation as the keystep or by derivation from D-(+)-glyceraldehyde acetonide.     

The influence of polytypic structures on the M011-->M101 solid-solid phase transition of n-C36H74: an application of the oblique infrared transmission method

The molecular displacements on the M011-->M101 phase transition of n-hexatriacontane (n-C36H74) have been investigated with an IR microscope designed for the oblique infrared transmission method. It has been clarified that two polytypic structures of the M011 modification, single-layered structure (Mon) and double-layered one (Orth II), both transform to the M101 modification of single-layered structure with their respective mechanisms. On the M011(Mon)-->M101 transition, the inclination direction of molecular axis is changed by 90 degrees through an intermediate state in which the molecular chain is set perpendicular to the basal plane of the single crystal. On the other hand, a polymorphic-polytypic composite structural change on the M011(Orth II)-->M101 transition is accomplished through two kinds of molecular displacements occurring alternately along the stacking direction of molecular layers.     

Symplectic curvature tensors

In the paper, one establishes the decomposition of the space of tensors which have the symmetries of the curvature of a torsionless symplectic connection into Sp (n)-irreducible components. This leads to three interesting classes of symplectic connections: flat, Ricci flat, and similar to the Levi-Civita connections of Kähler manifolds with constant holomorphic sectional curvature (we call them connections with reducible curvature). A symplectic manifold with two transversal polarizations has a canonical symplectic connection, and we study properties that are encountered if this canonical connection belongs to the classes mentioned above. For instance, in the reducible case we can compute the Pontrjagin classes, and these will be zero if the polarizations are real, etc. If the polarizations are real and there exist points where they are either singular or nontransversal, one has residues in the sense ofLehmann [L], which should be expected to play an interesting role in symplectic geometry.     

Synthesis of polyamides by the polyaddition of bisimidazoline with dicarboxylic acids

N,N′-Dipropionylethylenediamine was synthesized by the ring-opening addition reaction of 2-ethyl-2-imidazoline with propionic acid at 220°C. By applying this reaction to polymerization, polyamides were synthesized by the ring-opening polyaddition reaction at 220°C. of 1,4-bis(imidazoline-2-yl)butane with adipic acid, succinic acid, sebacic acid, and terephthalic acid. The reaction product of 1,4-bis(imidazoline-2-yl)butane with adipic acid, which was proposed to be nylon 26, was compared with an authentic sample of nylon 26 and shown to possess a very similar infrared spectrum and melting point.     

Foliate partial holomorphic structures on principal bundles

Thefoliate partial holomorphic (f.p.h.) pseudogroup is the pseudogroup of the local diffeomorphisms of ^m which preserve a distribution of the form span , wherey ^a are real coordinates,z are complex coordinates, and ^m may have also some other real coordinates. The f.p.h. structures on manifolds are described geometrically by the Nirenberg-Frobenius theorem [N], and occur in many interesting situations [R], [FW], [DK1], [V3], etc. The present paper discusses f.p.h. structures on principal bundles, and associates with such structures adapted connections, and forms with values in an associated bundle of Lie algebras.     

Riemannian manifolds with a parallel field of complex planes

The purpose of this paper is to discuss Riemannian manifolds which admit a parallel field of complex planes, consisting of vectors of the form , where a,b are real orthogonal vectors of equal length. Using the Nirenberg Frobenius Theorem [12], it follows that these are reducible Riemannian manifolds, whose metric is locally a sum of a Kähler and of a Riemann metric, and we are calling thempartially Kähler manifolds.After a general presentation of these manifolds (including a general presentation of the complex integrable plane fields) we are discussing harmonic forms, Betti numbers, and Dolbeault cohomology. This discussion is based on a theorem of Chern [4], and it provides generalizations of the results of Goldberg [9], as well as some other new results.To Prof. R. Artzy on his 70th Birthday     

A novel [60]fullerene receptor with a Pd(II)-switched bisporphyrin cleft

Porphyrin dimer 1, which does not have an inside cavity and cannot interact with [60]fullerene (C60), becomes an excellent C60-acceptor with a large cavity in the presence of a Pd(II) complex.     

On locally conformal almost Kähler manifolds

In the first section of this note, we discuss locally conformal symplectic manifolds, which are differentiable manifoldsV ²ⁿ endowed with a nondegenerate 2-form Ω such thatdΩ=θ ∧ Ω for some closed form θ. Examples and several geometric properties are obtained, especially for the case whendΩ ≠ 0 at every point. In the second section, we discuss the case when Ω above is the fundamental form of an (almost) Hermitian manifold, i.e. the case of the locally conformal (almost) Kähler manifolds. Characterizations of such manifolds are given. Particularly, the locally conformal Kähler manifolds are almost Hermitian manifolds for which some canonically associated connection (called the Weyl connection) is almost complex. Examples of locally conformal (almost) Kähler manifolds which are not globally conformal (almost) Kähler are given. One such example is provided by the well-known Hopf manifolds.