Paeonilactone-A, -B,and -C,new monoterpenoids from paeony root

Three new monoterpenoids named paeonilactone-A, -B, and -C were isolated from Paeony root (roots of Paeonia albiflora PALLAS var. trichocarpa BUNGE) and their structures were determined to be $\text{2}$, $\text{3}$, and $\text{4}$, respectively, by means of chemical and spectroscopic studies.     

ClickFerrophos: new chiral ferrocenyl phosphine ligands synthesized by click chemistry and the use of their metal complexes as catalysts for asymmetric hydrogenation and allylic substitution

The new ferrocenyl P,P- and P,N-ligands 5 and 6 (collectively, "ClickFerrophos") were readily prepared in four steps using Click Chemistry methodology, starting from the commercially available aminoferrocene 1. Rhodium and ruthenium complexes of ClickFerrophos 5 were effective catalysts for the hydrogenation of alkenes and ketones, respectively, producing products with up to 99.7% ee. The analogous palladium complex with 6 worked well for asymmetric allylic alkylation.     

Studies on cytotoxic constituents in pericarps of Mallotus japonicus. IV

Two new phloroglucinol derivatives, isomallotolerin (1) and isomallotochromanol (2), were isolated from the cytotoxic fraction of the pericarps of Mallotus japonicus. The new derivatives were identified as 3-(3-methyl-2-hydroxybut-3-enyl)-5-(3-acetyl-2,4-dihydroxy-5-methy l-6- methoxybenzyl)-phlorisobutyrophenone (1) and 6-acetyl-5,7-dihydroxy-8-(3-acetyl-2,4-dihydroxy-5-methyl-6-methoxybenzy l)-2,2- dimethyl-3-hydroxychroman (2) from chemical and spectral data. Isomallotolerin and its acetate were found to be cytotoxic to KB cell line.     

Interaction between charged soft microcapsules and red blood cells: effects of PEGylation of microcapsule membranes upon their surface properties

Four types of hydrophilic gel microcapsules containing water have been prepared by an interfacial polymerization method. Each type of microcapsules has a membrane of different composition. Using three kinds of monomers, N,N-dimethylacrylamide (DMAAm), 4-(aminomethyl)styrene (AmSt), and N,N-dimethylaminopropylacrylamide (DMAPAA), one type of aqueous copolymer having primary and tertiary amino groups was obtained. By the polymerization of three kinds of monomers, DMAAm, AmSt, and 2-[(methacryloyloxy)ethyl] trimethylammoniumchloride (METAC), another type of aqueous copolymer having primary and quaternary ammonium groups was also obtained. Two more types of copolymers were synthesized by copolymerization of -acryloxy-ω-methoxy-poly(ethylene glycol) (a-PEG) with the above two kinds of monomer mixture. These copolymers were polymerized with terephthaloyldichloride at the water/oil interface to prepare four types of microcapsules containing water, i.e., poly(DMAAm-co-DMAPAA-co-AmSt-alt-terephthalic acid) microcapsules, poly(DMAAm-co-DMAPAA-co-AmSt-co-PEG-alt-terephthalic acid) microcapsules, poly (DMAAm-co-METAC-co-AmSt-alt-terephthalic acid) microcapsules, and poly (DMAAm-co-METAC-co-AmSt-co-PEG-alt-terephthalic acid) microcapsules, which will be abbreviated to MC 1, MC 2, MC 3, and MC 4, respectively. It has been predicted that the microcapsule membranes are hydrophilic and soft and have two-sublayer structures from electrophoretic mobility measurements and from the analysis of the data with Ohshima’s electrokinetic theory for soft particles. The outer sublayers of MC 1 and MC 2 are negatively charged and those of MC 3 and 4 are slightly positively charged. Also, the surfaces of MC 1 and MC 2 are harder than those of MC 3 and 4. By PEGylation, the surface charge density in the membranes decreases and the surface becomes softer. It has been found that the membrane of red blood cells (RBC) is also soft and is composed of two-sublayers, the outer sublayer of which is negatively charged and the inner one is positively charged. The interaction of four types of microcapsules with RBC has been studied. It was found that microcapsules with soft surfaces (MC 3 and MC 4) do not interact with RBC, even though the microcapsule surfaces are positively charged and the surface of RBC is negatively charged. On the other hand, microcapsules with negatively charged but harder surfaces (MC 1) interact with RBC to introduce hemolysis. The membrane surface of MC 2, which is obtained by PEGylation of MC 1, becomes softer than that of MC 1 so that the interaction with RBC was weakly suppressed. From these, it was concluded that the dominant factor to control the interaction between synthetic polymer surfaces and biological cell surfaces is not the surface charges carried by the polymer surfaces but the softness of the polymer surfaces.     

Precise measurement of the self-diffusion coefficient for poly(ethylene glycol) in aqueous solution using uniform oligomers

Uniform poly(ethylene glycol) (PEG) oligomers, with a degree of polymerization n=1-40, were separated by preparative supercritical fluid chromatography from commercial monodispersed samples. Diffusion coefficients, D, for separated uniform PEG oligomers were measured in dilute solutions of deuterium oxide (D(2)O) at 30 degrees C, using pulsed-field gradient nuclear magnetic resonance. The measured D for each molecular weight was extrapolated to infinite dilution. Diffusion coefficients obtained at infinite dilution follow the scaling behavior of Zimm-type diffusion, even in the lower molecular weight range. Molecular-dynamics simulations for PEG in H(2)O also showed this scaling behavior, and reproduced close hydrodynamic interactions between PEG and water. These findings suggest that diffusion of PEG in water is dominated by hydrodynamic interaction over a wide molecular weight range, including at low molecular weights around 1000.     

The practical synthesis of (2S)-7-methoxy-1,2,3,4-tetrahydro-2-naphthylamine via optical resolution of 2-(3-methoxybenzyl)succinic acid

We describe the practical synthetic route for (2S)-7-methoxy-1,2,3,4-tetrahydro-2-naphthylamine 1(2S)-2-amino-7-methoxytetraline; (S)-AMT]. (2R)-2-(3-Methoxybenzyl)succinic acid [(R)-1] was obtained by the optical resolution of 2-(3-methoxybenzyl)succinic acid (1) as the salt of (1R,2S)-2-(benzylamino)cyclohexylmethanol (7), and (R)-1 was converted to the optically active (2S)-7-methoxy-1,2,3,4-tetrahydro-2-naphthoic acid [(S)-2] by the intramolecular Friedel-Crafts reaction followed by catalytic hydrogenation. (S)-AMT was obtained from the acid (S)-2 by Hofmann rearrangement without racemization.     

Ab initio MO study of the solvent effect on the SN2 reaction of the trimethylsulfonium cation with chloride anion

A recently developed ab initio MO theory including solvent effects has been applied to a typical cation-anion reaction, the S_N2 reaction of the trimethylsulfonium cation with the chloride anion. In the gas phase, the trimethylsulfonium and chloride ions are unstabilized, and the reaction is expected to proceed rapidly. In aqueous solution, the reactant ions are largely stabilized, and the reaction has been predicted to be endothermic, with an activation energy of 30–40 kcal/mol. This potential energy profile, which agrees with experimental results, has been well elucidated by differential solvation at several stages of the reaction path. At the transition state of this reaction, the C and H atoms in the transferring CH₃ group are almost in a plane that is perpendicular to the Cl(SINGLE BOND)C(SINGLE BOND)S line, reflecting the concerted nature of the reaction. The population analysis has shown that the electrons in the C(SINGLE BOND)S bond are mostly withdrawn by the sulfur atom at the transition state and that the electron transfer from Cl to CH₃ occurs after the transition state. The calculated activation energy for the reaction in ethanol is smaller than that in water. This agrees with experiments. © 1996 John Wiley & Sons, Inc.     

Highly sensitive near-infrared fluorescent probes for nitric oxide and their application to isolated organs

Novel near-infrared (NIR) fluorescent probes for nitric oxide (NO) have been designed, synthesized, and evaluated. Their NIR fluorescence was increased in an NO concentration-dependent manner under physiological conditions, and their reaction efficiency with NO was at least 53 times higher than that of a widely used NO probe, DAF-2. They were confirmed to function in isolated intact rat kidneys. Because NIR light can penetrate deeply into tissues, these probes may have potential for in vivo NO imaging.