Trypanocidal terpenoids from Laurus nobilis L

Trypanocidal constituents of dried leaves of Laurus nobilis L. (Lauraceae) were examined. Activity-guided fractionation of the methanol extract resulted in the isolation of two guaianolides, dehydrocostus lactone (1) and zaluzanin D (2), and a new p-menthane hydroperoxide, (1R,4S)-1-hydroperoxy-p-menth-2-en-8-ol acetate (3). The minimum lethal concentrations of these compounds against epimastigotes of Trypanosoma cruzi were 6.3, 2.5, and 1.4 microM, respectively.     

Infrared spectroscopic studies of polymer transitions. III. Effects of sodium ion on glass transitions in styrene-based ionomers

The glass transition in styrene-based ionomers was investigated by means of infrared spectroscopy and differential scanning calorimetry (DSC). Transition temperatures were determined from the temperature dependence of the peak absorbances of the 1700 and 1745 cm^?1 bands. These transition temperatures agreed with glass transition temperatures (T_g) determined by DSC. With increasing degree of ionization, T_g and the enthalpy ΔH of the residual intermolecular hydrogen bonding increased. The values of T_g obtained were analyzed by the theory of Fox and Loshaek for the effect of crosslinks. It is concluded that sodium ions probably from ionic domains and act as crosslinks to reinforce the residual hydrogen bonding and may increase T_g. The absorbance at 1560 cm^?1 (ν_COO^?) did not change at T_g. This suggests that the glass transition observed here is not due to the onset of the mobility in ionic domains, as has been proposed for ethylene-based ionomers on the basis of dielectric measurements.     

Preparation of sterically congested di(4-pyridyl)diazomethanes and characterization of triplet carbenes from them

Di(4-pyridyl)diazomethanes having two and four ortho chlorine groups were prepared, and the triplet carbenes generated from them were characterized by ESR and UV/vis at low temperature and time-resolved UV/vis at room temperature. An appreciable increase in the stability of triplet carbenes is achieved by introducing ortho chlorine groups. [structure: see text]     

syn-selective direct catalytic asymmetric Mannich-type reactions of hydroxyketones using Y{N(SiMe3)2}3/linked-BINOL complexes

[reaction, structure: see text] Chiral Y{N(SiMe3)2}3/linked-BINOL catalyst generated Y-enolate in situ from various hydroxyketones (R2 = aryl, heteroaryl). Beta-amino-alpha-hydroxy ketones (R1 = aryl, heteroaryl, alkenyl) were obtained syn-selectively (up to 96/4) in high ee (up to 98%) and good yield (up to 98% yield).     

Thermal splitting of Bis-Cu(II) octaphyrin(1.1.1.1.1.1.1.1) into two Cu(II) porphyrins

When heated, bis-Cu(II) octaphyrin(1.1.1.1.1.1.1.1) is quantitatively split into two Cu(II) porphyrins both in solution and film states, which is accompanied by large absorption spectral changes.     

Schulzeines A-C, new alpha-glucosidase inhibitors from the marine sponge Penares schulzei

Three new alpha-glucosidase inhibitors, schulzeines A-C (1-3), were isolated from the marine sponge Penares schulzei. Their structures were elucidated by spectral analysis and chemical degradations to be the isoquinoline alkaloids, encompassing two amino acids, and C(28) fatty acid, the last of which was sulfated. Absolute stereochemistry of schulzeines was determined by application of the modified Mosher analysis to fragments obtained by chemical degradation. Schulzeines A-C inhibit alpha-glucosidase with IC(50) values of 48-170 nM.     

Crystalline inclusion compounds constructed through self-assembly of isonicotinic acid and thiocyanato coordination bridges

The synthesis, crystal structures, inclusion ability, and structural robustness of novel crystalline inclusion compounds of [Ni(SCN)2(isoH)2].xG (isoH = isonicotinic acid; G = aromatic guest) are described. The inclusion compounds are constructed by stacking identical 2D host layers that consist of SCN-, isoH, and Ni2+ with van der Waals contact separation. In the layer, two types of rectangular cavities (A-type and B-type) are formed, and the guests are included in the former cavity. The inclusion compounds were categorized into four stacking modes according to the difference in the stacking mode of the layers. A systematic investigation of the crystal structures of the 21 inclusion compounds clarified the close relationship between the molecular structure of the guest and the resultant stacking mode of the layers.