Photocyclization of 2-azabicyclo[3.3.0]octane-3-carboxylate derivatives: induced and noninduced diastereoselectivity

[reaction: see text] The decarboxylative photocyclization of potassium 2-azabicyclo[3.3.0]octanoate ethylene-linked to phthalimide leads to a mixture of two diastereoisomeric products. The overall noninduced diastereoselectivity is remarkably high, indicating a preference of spin-orbit coupling controlled 1,7-biradical combination process. Memory of chirality vanished due to free rotation about the connecting spacer bonds.     

Formation of a tetranuclear copper (II) cluster assembled by metal-assisted hydrolysis and desulfurization of bis(3,5-dimethylpyrazolyl)methylphosphine sulfide, MeP(S)(3,5-Me2Pz)2

The reaction of methylphosphine sulfide, MeP(S)(3,5-Me2Pz)2, 1, with anhydrous CuCl2 affords a tetranuclear copper cluster[Cu2Cl2(3,5-Me2Pz)3(MePO3)]2, 2, and a dinuclear compound Cu2Cl4(3,5-Me2Pz)4, 3. This reaction involves a metal-assisted desulfurization along with concomitant hydrolysis of P-N bonds. The X-ray structures of 1-3 have been determined, and the crystal parameters for these are the following. 1: space group = C2/c, a = 15.2552(1) A, b = 8.7364(2) A, c = 21.4490(3) A, beta = 93.349(1) degrees, V = 2853.74(8) A3, and Z = 8. 2: space group = P2(1)/n, a = 12.5964(4) A, b = 15.7773(4) A, c = 13.9781(4) A, beta = 116.6280(10) degrees, V = 2483.32(12) A3, and Z = 2. 3: space group = P2(1)/c, a = 8.7137(8) A, b = 13.5493(14) A, c = 11.8847(12) A, beta = 106.179(2) degrees, V = 1347.6(2) A3, and Z = 2. The structure of 2 shows that it comprises two dinuclear copper cores bridged together by two tripodal methylphosphinate, MePO3, ligands. 2 is weakly antiferromagnetically coupled, as revealed by variable temperature magnetic susceptibility measurements.     

Spirophostins: conformationally restricted analogues of adenophostin A

The synthesis, biological evaluation, and molecular modeling of two conformationally restricted analogues of adenophostinA (1), denominated as spirophostin (3R)-10 and (3S)-11, as novel ligands for the D-myo-inositol 1,4,5-trisphosphate receptor (IP3R), is presented. These diastereoisomeric spiroketals are synthesized by spiroketalization of D-glucose derivatives (2S)-15 and (2R)-16, separation of the protected isomers (3R)-19 and (3S)-20, followed by phosphorylation and deprotection. The spirophostins (3R)-10 and (3S)-11 display comparable biological activity, with a 3H-IP3-displacing and Ca2+-releasing potency less than IP3 and adenophostin A.     

Introduction of heteroatom-based substituents into 1,4-dihydropyridines by means of a halogen-mediated, oxidative protocol: diamination, sulfonylation, sulfinylation, bis-sulfanylation, and halo-phosphonylation processes

The natural tendency of 1,4-dihydropyridines to undergo "biomimetic" oxidation to afford pyridinium salts can be switched off and, through the use of reagents that interact electrophilically with the enamine moiety present in the heterocyclic system, it is possible to promote alternative oxidations. In this way, efficient regio- and stereocontrolled synthetic methods have been developed that lead to diversely substituted di- and tetrahydropyridines. These include iodoazidation, diamination, bis-sulfonamidation, sulfonylation, sulfinylation, thiocyanation, sulfanylation, bis-sulfanylation, and halo-phosphonylation processes.     

Analysis of citrates and benzoates used in poly(vinyl chloride) by supercritical fluid extraction and gas chromatography

Supercritical fluid extraction (SFE) has been demonstrated to be a useful tool in the determination of additives in polymeric materials. This paper describes the determination of some citrates and benzoates in poly(vinyl chloride) blended with 33–34% of plasticizer using off-line SFE followed by gas chromatography. Experimental factors affecting SFE have been studied by gravimetric analysis, followed by analysis of the extracts using a gas chromatograph equipped with a flame ionization detector. The extraction process is governed by the solubility of the plasticizers in the supercritical fluid or by their diffusion through the polymer matrix, which depend on the pressure and temperature used. Maximum extraction (>99%) is obtained at pressures and temperatures higher than 40 MPa and 80 °C, respectively. Due to purge losses, the collection efficiency of plasticizers into a liquid solvent ranges from 85 to 90%. The applicability of the SFE method is demonstrated using real samples and comparing the results with those obtained by conventional Soxhlet extraction.     

表示水的硬度的新单位

水的硬度由其中钙盐、镁盐(有时有两价的铁盐)含量的多少来决定。水的硬度通常以相对硬度来表示。各国硬度的表示法有所不同,多以某种体积水中CaO或CaCO_3的含量为基础。其他两价金属换算成等当量的钙化合物来计算。以前苏联用100升水中含1克CaO,即是在1升水中含10毫克CaO来表示水的硬度。在很早以前,当时在化学界中统治着盐的是由金属氧化物和非金属氧化物形成(例如由CaO和CO_2所形成的CaCO_3)的二元论的学说,就应用过     

A conducting crystal based on a single-component paramagnetic molecule, [Cu(dmdt)(2)] (dmdt = dimethyltetrathiafulvalenedithiolate)

A single-component conducting molecular crystal composed of paramagnetic copper complexes, [Cu(dmdt)2]0+, was prepared. The crystal has an unprecedented three-dimensionally packed molecular arrangement and exhibits a fairly high conductivity (1 S cm-1 at room temperature). The magnetic susceptibility measurements revealed that [Cu(dmdt)2]0+ molecule keeps most of S = 1/2 spin moments. The difference of the bond lengths between [Cu(dmdt)2]0+ and [Cu(dmdt)2]2- is consistent with the result of the molecular orbital calculation.     

Constituents of holothuroidea.9. Isolation and structure of a new ganglioside molecular species from the sea cucumber Holothuria pervicax

A new ganglioside molecular species, HPG-7 (1) was obtained from the polar fraction of the chloroform/methanol extract of the sea cucumber, Holothuria pervicax. On the basis of chemical and spectroscopic evidence, the structure of 1 was determined, and the major component was 1-O-[alpha-L-fucopyranosyl-(1-->4)-(N-acetyl-alpha-D-neuraminosyl) - (2-->11)-(N-glycolyl-alpha-D-neuraminosyl)-(2-->4)-(N-acetyl -alpha-D- neuraminosyl)-(2-->6)-beta-D-glucopyranosyl]-(2S,3S,4R)-2-[(2R)-2- hydroxytetracosanoylamino]-14-methyl-hexadecane-1,3,4-triol. This is the first report on the isolation and structure elucidation of trisialo-ganglioside from sea cucumber. 1 showed neuritogenic activity toward the rat pheochromocytoma cell line, PC-12 cell.     

Immunological and biochemical evidence that blepharismin is not a prosthetic group

A polyclonal, multispecific antiserum was raised against a whole 3[(3-cholamidopropyl)-dimethylammonio]-1-propanesulfonate-extract of nonirradiated Blepharisma japonicum cells. It was used to reveal the composition of solutions that were hypothesized to contain the photoreceptor of the ciliate. A Bio-Gel A 1.5 m fine column chromatography of the extract allowed recovery of a single elution peak isolated by recording the 580 nm light absorbance. Fused-rocket immunoelectrophoresis of this material revealed a large number of > 300 kDa coeluted proteins. Blepharismin-rich material with a molecular mass of approximately 50 kDa, consisting of at least nine proteins was obtained when the same extract underwent preparative isoelectric focusing before column chromatography separation. Purification of the pigment obtained from light-exposed cells gave blepharismin-rich material with a molecular weight of approximately 200 kDa. Comparison of the materials obtained under the same conditions, either from the dark-kept or light-irradiated cells, by means of pore-gradient electrophoresis confirmed that proteins present in the two preparations were different. It revealed only a very small amount, if any, of proteins in the chromatography fractions with the highest absorbance at 600 nm. Results are discussed on the basis of the hypothesis that a specific blepharismin-binding protein does not exist in the protozoan.