Switching catalytic reaction conducted in pore void of mesoporous material by redox gate control

A molecular gate attached on the pore outlet of a mesoporous material, which is opened and closed by redox system of thiol groups, effectively switched the progress of a catalytic reaction promoted by the acidic site in the pore void.     

Total synthesis of brevenal

The convergent total synthesis of brevenal, a non-toxic brevetoxin antagonist, has been achieved. The ABC ring segment and the E ring precursor were connected by the intramolecular allylation followed by ring-closing metathesis to furnish the pentacyclic ether compound. An alternative route to the key synthetic intermediate, a pentacyclic ether core, was also examined. The right- and left-hand side chains were introduced by Wittig and Horner-Wadsworth-Emmons reactions, respectively, to furnish brevenal (1).     

Stereocontrolled synthesis and structural confirmation of the C14-C24 degraded fragment of symbiodinolide

The C14-C24 fragment of symbiodinolide possessing the 17R/18R/21R absolute configuration, which was obtained as one of the degraded products of symbiodinolide, and its diastereomer possessing the 17R/18S/21R absolute stereochemistry were synthesized stereoselectively from cis-2-butene-1,4-diol, respectively. The detailed comparison of the synthetic products with the degraded product in the spectroscopic data confirmed unambiguously that the stereostructure of the C14-C24 fragment was 17R, 18R, and 21R.     

Carboxymethyl poly(L‐histidine) as a new pH‐sensitive polypeptide at endosomal/lysosomal pH

A carboxymethyl poly(L ‐histidine) has been synthesized as a new pH‐sensitive polypeptide at endosomal/lysosomal pH. Because of its poor water solubility at physiological pH, an application of poly(L ‐histidine) with a pK_a around 6.0 has been limited in spite of the native possession of the pH‐dependent property change at endosomal pH. Although the unmodified poly(L ‐histidine) suddenly precipitates out of the aqueous medium above pH 6.0 as the result of the deprotonation of the imidazole groups, the water solubility of the resulting carboxymethyl poly(L ‐histidine) has been improved at physiological pH. A solution turbidity measurement proved that no significant effect on a rapid aggregate formation or phase separation of serum proteins is induced by carboxymethyl poly(L ‐histidine). Hemolysis assay showed that the carboxymethyl poly(L ‐histidine) enhances membrane disruptive ability at endosomal/lysosomal pH. The cellular uptake of luciferase in the presence of the carboxymethyl poly(L ‐histidine) increases intracellular luciferase activity, which suggests that the carboxymethyl poly(L ‐histidine) makes the luciferase escape from lysosomal degradation. The carboxymethyl poly(L ‐histidine) would be the fundamental compound for designing various drug carriers with the pH sensitivity at endosomal/lysosomal pH. Copyright © 2007 John Wiley & Sons, Ltd.     

Polymerization of allyl(vinyl phenyl) ethers and reactions of the resulting polymers

Solution polymerizations of allyl(o-vinyl phenyl)ether and allyl(p-vinyl phenyl)ether with cationic and radical initiators were investigated. Soluble polymers were formed in polymerizations with boron trifluoride etherate and with benzoyl peroxide. In polymerization with azobisisobutyronitrile the polymerization in dilute solution gave a soluble polymer, whereas that in concentrated solution gave a crosslinked, insoluble one. For informationon the polymerization behavior some infrared and ultraviolet spectroscopic investigations of the soluble polymers were made. From these results it appears that polymers with pendant allyl groups are formed in polymerization with boron trifluoride etherate at low temperature, and polymers containing pendant vinyl groups and allyl groups are obtained with the two types of radical initiator. Copolymerizations of these monomers with ethyl vinyl ether and styrene with the use of boron trifluoride etherate were sucessfully effected. Such reactions as Claisen rearrangement, crosslinking induced with radical initiators, and epoxidation with perbenzoic acid were examined for the polymers prepared in the polymerization with boron trifluoride etherate. Good results were obtained for the former two reactions. However, the latter was unsuccessful.     

Polymerization behavior of N-(p-vinyl)phenylacrylamide

The polymerization behavior of N-(p-vinyl)phenylacrylamide, synthesized from p-aminostyrene and acryloyl chloride by means of the Schotten-Baumann reaction was studied. Due to a marked difference in electron density between the two double bonds, this monomer provided soluble polymers by both cationic and anionic polymerization procedures, the cationic and anionic polymers mainly carrying, as side chains, the acrylamide and styrene moieties, respectively. The polymerization behavior of the residual double bonds was also investigated for both polymers, leading to crosslinked, insoluble products.     

Synthesis of stereoregular heteropolysaccharides having amino-groups by ring-opening copolymerization of 1,6-anhydro-azido-sugar derivatives

The cationic, ring-opening copolymerization of 1,6-anhydro-2-azido-3,4-di-0-benzyl-2-deoxy-(2-ABG), -3-azido-2,4-di-0-benzyl-3-deoxy- (3-ABG), -4-azido-2,3-di-0-benzyl-4-deoxy-β-D -glucopyranose (4-ABG) with 1,6-anhydro-2,3,4-tri-0-benzyl-β-D -glucopyranose (LGTBE) was investigated with phosphorus pentafluoride as catalyst at low temperatures, giving highly stereoregular, (1→6)-α-linked copolymers with number-average molecular weights of 3.90 × 10⁴?9.27 × 10⁴. Structure and composition of the copolymers were determined by ¹H- and ¹³C-NMR spectroscopies and elemental analysis, which indicated that copolymerization occurred in a stereoregular manner to give azido groups containing (1→6)-α-linked glucopyranan derivatives. The differences in polymerizability among the three azido monomers are discussed. Regioselective reduction of three kinds of heteropolysacharide derivatives which had different quantities of azido groups at C-2, -3, or -4 position with lithium aluminum hydride and subsequent debenzylation of the copolymers with sodium in liquid ammonia produced amino-group-containing heteropolysaccharides.     

Cyclotron resonance in lead —I: Tipping effect of magnetic field

The cyclotron resonances in lead in field tipped geometry have been observed for large tipping angles up to 40° from the sample surfaces of the (111) and (100) planes. In addition to the resonance of the orbit ζ on a cylindrical arm of the electron Fermi surface, two new series of resonances, ζ^A and ζ^B have been found, of which the clotron masses are very close to that of ζ but which differ slightly in tipping angle dependence. The mass of ζ^A is dependent on microwave frequency, so that ζ^A is attributed to the Doppler-shifted cyclotron resonance of a non-stationary orbit near, ζ, whose location is discussed in relation to the Fermi surface model of Van Dyke. In field geometry normal to the (100) surface, two series of resonances have been observed, which are characterized as the extinction of even numbered harmonic resonances. This effect arises from the skipping orbit which has a trajectory topologically similar to a baseball seam in real space. One of these series is attributed to the orbit v around the junction of four electron arms.     

Studies on polymers containing functional groups. III. Charge-transfer interaction between quinone and aza polymers

Absorption maxima and equilibrium constants for charge-transfer complexes between quinone and aza polymers, such as poly-2-vinylpyridine, poly-4-vinylpyridine, poly-2-methyl-5-vinylpyridine, and poly-N-dimethylaminomethylacrylamide, were determined spectrophotometrically. For comparison, those for charge-transfer complexes between quinone and aza compounds, such as pyridine, methyl-substituted pyridines, quinoline, triethylamine, and dimethylaniline were also presented. It was found that the equilibrium constants for polymer complexes are always larger than those for the corresponding monomer complexes, while the time required for attaining the equilibrium was longer for polymer complexes than for monomer complexes. In the interaction between quinone and poly-N-dimethylaminomethylacrylamide, two absorption maxima which gradually shifted towards each other were observed. The same phenomenon was found in the interaction between quinone and the corresponding monomer, triethylamine.