Biologically active glycosides from asteroidea, 42. Isolation and structure of a new biologically active ganglioside molecular species from the starfish Asterina pectinifera

A ganglioside molecular species GP-3 (1) has been obtained from the water-soluble lipid fraction of the chloroform/methanol extract of the starfish Asterina pectinifera. The structure of the ganglioside has been determined on the basis of chemical and spectroscopic evidence. Compound 1 represents new ganglioside molecular species possessing two moles of sialic acids at the inner part of the sugar moiety. Partial hydrolysis by hot water and an enzymatic hydrolysis by means of endoglycoceramidase (EGCase) have proved useful for structure elucidation of the complex oligosaccharide moiety. Moreover, 1 exhibits neuritogenic activity toward the rat pheochromocytoma cell line, PC-12 cells, in the presence of nerve growth factor (NGF).     

Glycosides of 14,15-seco and 13,14:14,15-disecopregnanes from the roots of Cynanchum sublanceolatum

Thirty-two new 13,14-seco and 13,14:14,15-disecopregnane glycosides were obtained from the roots of Cynanchum sublanceolatum (Asclepiadaceae). These glycosides were confirmed to be possessing five known compounds, cynajapogenin A, glaucogenin-A, 13-hydroxycynajapogenin A, 2alpha-hydroxyanhydrohirundigenin, atratogenin A and one new pregnane, 13-epi-cynajapogenin A, as their aglycones, using both spectroscopic and chemical methods.     

Novel synthesis of (Z)-difluoroacrylates via a highly stereoselective addition-elimination reaction

[STRUCTURE: SEE TEXT] On treating readily prepared benzyl 2,3,3-trifluoroacrylate with various Grignard reagents, e.g., aryl-, alkyl-, or alkenylmagnesium halide, in the presence of a catalytic amount of copper(I) salt in THF at -78 degrees C for 1 h, the corresponding alpha,beta-difluoroacrylates were obtained in 54-98% yields with high Z-selectivity.     

Sequential formation of a ternary complex among dihexylammonium, cucurbit[6]uril, and cyclodextrin with positive cooperativity

[STRUCTURE: SEE TEXT] A unique ternary 1:1:1 cucurbit[6]uril (CB[6])-cyclodextrin (CD)-dihexylammonium (DHA) complex was designed and noncovalently synthesized in stepwise fashion: first, CB[6] interacts strongly with DHA to form a 1:1 complex; second, addition of CD into the solution of the 1:1 complex leads to the exclusive formation of the 1:1:1 ternary complex. The ternary complex was characterized by various experimental techniques including ITC, NMR, and ESI-MS.     

Supramolecular chiral recognition by bischlorins: a two-point interaction mode combined with the host's conformational modulation controlled by the guest's stereochemistry and bulkiness

[reaction: see text] Supramolecular chiral recognition based on two-point host-guest interactions coupled with the different host's conformational response using the enantiopure bischlorin hosts and different antipodal amine guests is reported. The bulkiness at the guest's stereogenic center controls the chiral recognition properties resulting in switching of the enantioselectivity.     

Chelation-assisted transformation: synthesis of 1,4-dicarboxylate esters by the Rh-catalyzed carbonylation of internal alkynes with pyridin-2-ylmethanol

The reaction of internal alkynes 1 with CO and pyridin-2-ylmethanol (2) in the presence of Rh(4)(CO)(12) results in a double-hydroesterification leading to 1,4-dicarboxylate esters 3. The reaction does not proceed via two consecutive hydroesterifications of alkynes, but the intermediacy of ketene intermediates is proposed. The coordination of the pyridine nitrogen in 2 to rhodium is essential for the reaction to proceed. [reaction: see text]     

Electron conductive three-dimensional polymer of cuboidal C60

Single crystals of three-dimensional (3D) C60 polymer were prepared by the topotactic conversion of two-dimensional (2D) C60 polymer single crystals at a pressure of 15 GPa at 600 degrees C. The x-ray single crystal study revealed that the 3D C60 polymer crystallized in a body centered orthorhombic space group Immm, and spherical C60 monomer units were substantially deformed to rectangular parallelepiped (cuboidal) shapes, each unit being bonded to eight cuboidal C60 neighbors via [3 + 3] cycloaddition. The 3D C60 polymer was electron conductive, in contrast with the nonconductive behavior of 2D polymers.     

Extraordinary plasticity of ductile bulk metallic glasses

Shear bands generally initiate strain softening and result in low ductility of metallic glasses. In this Letter, we report high-resolution electron microscope observations of shear bands in a ductile metallic glass. Strain softening caused by localized shearing was found to be effectively prevented by nanocrystallization that is in situ produced by plastic flow within the shear bands, leading to large plasticity and strain hardening. These atomic-scale observations not only well explain the extraordinary plasticity that was recently observed in some bulk metallic glasses, but also reveal a novel deformation mechanism that can effectively improve the ductility of monolithic metallic glasses.     

Dynamic portfolio optimization with risk control for absolute deviation model

In this paper, we present a new multiperiod portfolio selection with maximum absolute deviation model. The investor is assumed to seek an investment strategy to maximize his/her terminal wealth and minimize the risk. One typical feature is that the absolute deviation is employed as risk measure instead of classical mean variance method. Furthermore, risk control is considered in every period for the new model. An analytical optimal strategy is obtained in a closed form via dynamic programming method. Algorithm with some examples is also presented to illustrate the application of this model.