Synthesis of thromboxane A2 analog DL-(9,11), (11,12)-dideoxa-(9,11)-epithio-(11,12)-methylene-thromboxane A2

A synthesis of the thromboxane A₂ analog, $\text{dl}$-(9,11), (11,12)-dideoxa-(9,11)-epithio-(11,12)-methylene-thromboxane A₂ is described.     

Fullerenols revisited as stable radical anions

The first exhaustive purification and characterization of the much-studied "fullerenols", prepared by reaction of C(60) in toluene with an oxygenated, aqueous NaOH solution using tetrabutylammonium hydroxide as a phase transfer catalyst, has been performed. The resulting fullerenol is not simply polyhydroxylated C(60) but rather is a structurally and electronically complex C(60) radical anion with a molecular formula of Na(+)(n)[C(60)O(x)(OH)(y)](n)(-) (where n = 2-3, x = 7-9, and y = 12-15) for three different, but identical, preparations. Surprisingly, Na(+)-fullerenol is paramagnetic, exhibiting mu(B) values in aqueous solution of 1.9-2.1 B.M. at 0.5 T and 300 K and R(1) proton relaxivities of 0.55-0.77 mM(-1)s(-1) at 20 MHz and 40 degrees C, values both slightly higher than those expected for a pure S = 1/2 spin system. ESR studies (ESE-FS and 2D nutation) of frozen aqueous solutions at 1.5 and 5.0 K establish that Na(+)-fullerenol is mainly S = 1/2 with a minor, but significant, component of S = 1. Thus, this is the first report to characterize these widely studied, water-soluble fullerenols as stable radical anions. The stability of the S = 1/2 Na(+)-fullerenol radical is likely due to a highly derivatized C(60) surface that protects a cyclopentadienyl radical center on the fullerene.     

The crystal structures of α- and β-CdUO4

The structural parameters of α- and β-CdUO₄ crystals are determined by X-ray powder diffraction technique. α-CdUO₄ is rhombohedral and cell parameters are a = 6.233(3) Å and α = 36.12(5)°. β-CdUO₄ crystallizes in a C-centered orthorhombic cell with a = 7.023(4), b = 6.849(3), c = 3.514 (2) Å. The space groups are $\text{R}\text{3}\text{m}$ for α-CdUO₄ and Cmmm for β-CdUO₄. α-CdUO₄: 1U in (000), 1Cd in ($\text{1}\text{2}\text{1}\text{2}\text{1}\text{2}$), 2O(1) in ±(uuu), 2O(2) in ±(vvv); u = 0.113, v = 0.350, Z = 1. β-CdUO₄: 2U in ($\text{000;}\text{1}\text{2}\text{1}\text{2}\text{0}$), 2Cd in ($\text{1}\text{2}\text{0}\text{1}\text{2}\text{; 0}\text{1}\text{2}\text{,}\text{1}\text{2}$), 4O(1) in ($\text{0, ±y, 0;}\text{1}\text{2}\text{,}\text{1}\text{2}\text{±y, 0}$), 4O(2) in ($\text{±x, 0,}\text{1}\text{2}\text{;}\text{1}\text{2}\text{±x,}\text{1}\text{2}\text{,}\text{1}\text{2}$); x = 0.159, y = 0.278, Z = 2. β-CdUO₄ contains collinear uranyl UO²⁺₂ groups with a UO(1) distance of 1.91 Å, located either along or parallel to the c axis whereas the UO(1) bond length in α-CdUO₄ is 1.98 Å which is longer than the usual uranyl bond length.     

Vortex shedding from a ring in shear flow

Vortex shedding from a bluff ring in a linear shear flow has been investigated experimentally. The shedding frequency, measured using a hot wire in various positions within the near wake of the ring, was found to be remarkably insensitive to a mean flow shear parameter, , defined by (d/U _o).U/y, where d is the mean ring diameter and U _o is the undisturbed upstream velocity on the ring axis; even for = 0.41, corresponding to a velocity variation of about ±24% across the outer ring diameter, the Strouhal number was only about 5% lower than in uniform flow. However, the strong axisymmetric shedding which dominates the flow for = 0 is significantly affected by shear. Indeed, spatial correlation measurements demonstrated that the shedding actually becomes anti-symmetric at the highest values of . The implication of these results is that vortex flowmeters constructed using a ring as the shedding body would be relatively unaffected by changes in the upstream mean flow profile.     

Ageladine A: an antiangiogenic matrixmetalloproteinase inhibitor from the marine sponge Agelas nakamurai

A novel MMP inhibitor, ageladine A (1) with antiangiogenic activity was isolated from a marine sponge Agelas nakamurai. Structure 1 was determined by a combination of spectroscopic and chemical methods to be an unprecedented structure of 4-(4,5-dibromo-1H-pyrrol-2-yl)]-1H-imidazo[4,5-c]pyridin-2-amine.     

Direct UHV-TEM observation of palladium clusters on a silicon surface.

About 1 monolayer of palladium was deposited onto a silicon (111) 7 x 7 surface at a temperature of about 550 K inside an ultrahigh vacuum transmission electron microscope, resulting in formation of Pd2Si nanoislands and a 1 x 1 surface layer. Pd clusters created from an excess of Pd atoms on the 1 x 1 surface layer were directly observed by in situ plan view high-resolution transmission electron microscopy. When an objective aperture was introduced so that electron diffractions less than 0.20 nm were filtered out, the lattice structure of the 1 x 1 surface with 0.33 nm spacing and the Pd clusters with a trimer shape were visualized. It was found that image contrast of the 1 x 1 lattice on the specific height terraces disappeared, and thereby an atomic structure of the Pd clusters was clearly observed. The appearance and disappearance of the 1 x 1 lattice was explained by the effect of the kinematical diffraction. It was identified that a Pd cluster was composed of three Pd atoms without a centered Si atom, which is consistent with the model proposed previously. The feature of the Pd clusters stuck at the surface step was also described.     

Polymer-Supported dicyanoketene acetal as a pi-acid catalyst: monothioacetalization and carbon-carbon bond formation of acetals

Polymeric dicyanoketene acetals (DCKA) were synthesized by copolymerization of styrene and divinylbenzene or ethylene glycol dimethacrylate. These novel polymers could be used successfully as recyclable pi-acid catalysts in monothioacetalization or carbon-carbon bond forming reaction of acetals.     

Immobilization of chlorophyll derivatives into mesoporous silica and energy transfer between the chromophores in mesopores

Chlorophyll derivatives possessing triethoxysilyl groups have been synthesized for the first time and grafted on mesoporous silica to construct an efficient energy transfer system between the chromophores.     

1,3,8,10-Tetrahydro-2,9-diazadibenzo[cd,lm]perylenes: synthesis of reduced perylene bisimide analogues

A unique family of 1,3,8,10-tetrahydro-2,9-diazadibenzo[cd,lm]perylenes (THDAP) was prepared through a new synthetic strategy. Completion of the synthesis was achieved in several steps from commercially available perylene-3,4,9,10-tetracarboxylic dianhydride via reactions between 3,4,9,10-tetra(chloromethyl)perylene and primary amines. The successful use of a variety of primary amines in the reactions indicated that the synthetic approach provides a rich opportunity to produce new functionalized perylene derivatives.