Structures of cytotoxic products from Fe-catalyzed oxidation of sesamol in ethanol

The iron-ion catalyzed oxidation of ethanol solution of sesamol, a potent antioxidant of sesame, afforded two significant cytotoxic products to normal mammalian cells. The structures were determined using extensive NMR spectroscopy as a new sesamol trimer and tetramer.     

Synthesis and chiroptical properties of amino acid-derived poly(methylpropargyl ester)s

Chiral methylpropargyl ester monomers containing amino acid moieties, N-(tert-butoxycarbonyl)-l-alanine (R)-1-methylpropargyl ester (1), N-(benzyloxycarbonyl)-l-valine (R)-1-methylpropargyl ester (2), and N-(tert-butoxycarbonyl)-l-O-cyclohexyl-l-glutamic acid (R)-1-methylpropargyl ester (3) were synthesized and polymerized with (nbd)Rh⁺[η⁶-C₆H₅B⁻(C₆H₅)₃] to give the corresponding polymers with number-average molecular weights ranging from 32 700 to 64 100 in 84-85% yields. The polymers were soluble in toluene, CHCl₃, CH₂Cl₂, THF, DMF, and DMSO, but insoluble in hexane, diethyl ether, and MeOH. The specific rotation and circular dichroism (CD) spectroscopic studies revealed that poly(1)-poly(3) took predominantly one-handed helical structures in the solvents, wherein the degree of one-handedness and tightness of the helix depended on the solvent. The helical structure of the polymers was stable to the addition of MeOH and heat.     

Fern constituent: colysanoxide,and onoceroid having a novel carbon skeleton,isolated from colysis species

A new triterpenoid named colysanoxide (II) having a novel carbon skeleton has been isolated from the leaves of Colysis elliptica and C. pothifolia, together with α-onoceradiene from the latter. The structure of II was established by spectroscopic, chemical and X-ray diffraction methods.     

Open Algebraic Surfaces with Finite Group Actions

Suppose that a finite group G acts algebraically on a log projective surface (V, Delta) in such a way that Delta is G-stable. Suppose kappa(V - Delta) union SingV) = -infinity We first look for the conditions under which the Mori theory can be applied equivariantly and observe what we obtain from the Mori theory. We then consider the P¹-fibrations which are preserved by the actions of G.     

Rhodium(I)-catalyzed silylation of aryl halides with triethoxysilane: practical synthetic route to aryltriethoxysilanes

[reaction: see text] The specific silylation of aryl iodides and bromides with triethoxysilane (EtO)(3)SiH in the presence of NEt(3) and a catalytic amount of [Rh(cod)(MeCN)(2)]BF(4) provides the corresponding aryltriethoxysilanes in high yield.     

Bacopasides III-V: three new triterpenoid glycosides from Bacopa monniera

Three new saponins, designated as bacopasides III, IV and V have been isolated from Bacopa monniera WETTST. and their structures have been elucidated as 3-O-alpha-L-arabinofuranosyl (1-->2)-beta-D-glucopyranosyl jujubogenin (1), 3-O-beta-D-glucopyranosyl (1-->3)-alpha-L-arabinopyranosyl jujubogenin (2) and 3-O-beta-D-glucopyranosyl (1-->3)-alpha-L-arabinopyranosyl pseudojujubogenin (3) mainly on the basis of two dimensional (2D) NMR and other spectral analyses.     

Surface conduction on insulating BaTiO3 crystal suggesting an intrinsic surface electron layer

We report conduction measurements on the clean, free surface of transparent insulating BaTiO3 single crystals in high vacuum. We find that the insulating BaTiO3 crystals exhibit surface conductance that is dependent on the spontaneous polarization, whereas no conduction perpendicular to the surface is observed. The surface conduction shows semimetallic temperature dependence and persists down to at least 100 K. The observations suggest a two-dimensional electron on a clean, free ferroelectric surface that may be regarded as a ferroelectric metal. The results have important implications for understandings of the fundamental properties of ferroelectrics, the size effect, and ferroelectric devices.     

Multilayer structure of an unsymmetrical monolayer lipid membrane with a 'head-to-tail' interface

A synthetic unsymmetrical 1-galactosamide bolaamphiphile self-assembles in methanol to form a multilayer structure comprising unsymmetrical monolayer lipid membranes linked via a sugar-carboxylic acid H-bonding interface.