Gelation in free-radical terpolymerization of poly(allyl methacrylate) crosslinked polymer nanosphere with allyl benzoate and vinyl benzoate

Microgel-like poly(allyl methacrylate) (PAMA nanosphere) was prepared by the emulsion polymerization of AMA as the reactive crosslinked polymer nanosphere with abundant pendant allyl groups. The terpolymerization of PAMA nanosphere with allyl benzoate (ABz) and vinyl benzoate (VBz) was conducted in bulk using benzoyl peroxide as initiator at 80 °C. The gelation depended on the feed ABz/VBz molar ratio since the molecular weights of resulting poly(ABz-co-VBz)s that act as the bridges increased with an increase in the mole fraction of VBz in the feed monomer. Beyond the gel point, the sol was rapidly incorporated into the gel and the increasing tendency of the gel fraction became steeper from 70 to 95 mol% of VBz as a reflection of increased chain length of bridge between PAMA nanospheres. Moreover, the swelling ratio became lower with increasing the mole percentage of VBz in the feed monomer. These results would support the preferential incorporation of PAMA nanosphere into the gel and the longer bridge can capture more nanospheres to give a much shrunken gel.     

Mechanism of antioxidative activity of fluvastatin-determination of the active position

In order to clarify the mechanism of action for the antioxidative activity of fluvastatin sodium (FLV, (+/-)-sodium (3RS, 5RS, 6E)-7-[3-(4-fluorophenyl)-1-(1-methylethyl)-1H-indol-2-yl]-3, 5-dihydroxy-6-heptanoate) and its derivatives, reaction of the corresponding methyl ester of FLV with di-tert-butyl diperoxyoxalate was examined, and the corresponding keto derivative was isolated from the reaction mixture. On the basis of this result, it was concluded that the active site is the allylic carbon conjugated with the indole ring.     

Asymmetric skeletal rearrangement of symmetrically alpha,alpha-disubstituted alpha-amino aldehydes: a new entry to optically active alpha-hydroxy ketones

A unique asymmetric skeletal rearrangement of symmetrically alpha,alpha-disubstituted alpha-amino aldehydes has been accomplished for the first time using a chiral organoaluminum Lewis acid 1. For instance, treatment of (S)-2,2'-bis(trifluoromethanesulfonylamino)-1,1'-binaphthyl with Me3Al (1.0 equiv) in toluene at room temperature for 15 min and at 110 degrees C for an additional 15 min produced (S)-1, and a subsequent reaction with alpha -amino aldehyde 2a (R = CH2Ph) at -78 degrees C for 4 h and at -40 degrees C for 12 h resulted in the smooth rearrangement to the zwitterionic iminium intermediate A, which furnished the alpha-hydroxy ketone 3a (R = CH2Ph) in 93% isolated yield with 95% ee (S) after acidic hydrolysis. This result, together with other representative examples, clearly demonstrates the effectiveness of the present method for the hitherto difficult asymmetric synthesis of acyloins. Furthermore, we found that the treatment of the in situ generated A with DIBAH afforded the corresponding anti amino alcohol exclusively without loss of enantiomeric excess. Our approach casts light on the previously unexplored yet potential utility of alpha-amino aldehydes as synthetic building blocks and also provides a new entry to optically active alpha-hydroxy ketones and 1,2-amino alcohols.     

Polycyclic N-hetero compounds. XXVII. Synthesis and investigation of the antidepressive activity of a B-Homo-11,13,15-triazasteroid and its related compoundsd

A synthesis of 1,2,5,6-tetrahydro-4H-benzo[3,4]cyclohepta[1,2-e]imidazo[1,2-c]pyrimidine (XII) having a novel ring system is described. Antidepressive activity of XII and its precursors VII-X was screened by inhibitory action of reserpine-induced hypothermia.     

Anticoagulant activity of immobilized thrombomodulin

Bovine lung thrombomodulin was partially purified, and immobilized on agarose gel (Sepharose 4B). Immobilized thrombomodulin inhibited the procoagulant activity of thrombin, and enhanced the thrombin-catalyzed protein C activation. The plasma recalcification time test showed that immobilized thrombomodulin prolonged plasma clotting time. It is suggested that the immobilization of thrombomodulin will provide an antithrombogenic biomaterial able to convert thrombin from a procoagulant to an anticoagulant enzyme.     

[2]Paracyclo[2](3,7)-p-tropoquinonophane

The title compound $\text{1}$ a novel cyclophane containing p-tropoquinone, was synthesized starting from 5-methoxytropolone and its physical properties were discussed comparing with those of 3,7-dimethyl-p-tropoquinone and p-benzoquinonophane. The reduced quinone character exhibited by $\text{1}$ was ascribed to the intramolecular CT interaction and the deformation of the quinone ring.     

Quenching of bacteriochlorophyll fluorescence in chlorosomes from Chloroflexus aurantiacus by exogenous quinones

The quenching of bacteriochlorophyll (BChl) c fluorescence in chlorosomes isolated from Chloroflexus aurantiacus was examined by the addition of various benzoquinones, naphthoquinones (NQ), and anthraquinones (AQ). Many quinones showed strong quenching in the micromolar or submicromolar range. The number of quinone molecules bound to the chlorosomes was estimated to be as small as one quinone molecule per 50 BChl c molecules. Quinones which exhibit a high quenching effect have sufficient hydrophobicity and one or more hydroxyl groups in the alpha positions of NQ and AQ. Chlorobiumquinone has been suggested to be essential for the endogenous quenching of chlorosome fluorescence in Chlorobium tepidum under oxic conditions. We suggest that the quenching effect of chlorobiumquinone in chlorosomes from Chl. tepidum is related to the 1'-oxo group neighboring the dicarbonyl group.     

Synthesis of aromatic polyamides by 1-hydroxybenzotriazole-catalyzed polycondensation of active aromatic diesters with aromatic diamines

Catalytic actions of various additives were studied in the polycondensation of di(4-nitrophenyl) isophthalate with bis(4-aminophenyl) ether in N-methyl-2-pyrrolidone, and 1-hydroxybenzotriazole (HOBt) was found to be a highly effective catalyst that yielded high-molecular-weight polyamide. In addition to the polycondensation of the 4-nitrophenyl ester, the polymerization of negatively substituted phenyl esters like di(2,4,5-trichlorophenyl) isophthalate was also accelerated by HOBt. For the HOBt-catalyzed aminolysis of esters a bifunctional concerted mechanism that involves an eight-membered transition state was proposed.     

α-Carboxylation reaction of carbonyl compounds with bromomagnesium ureide-carbon dioxide adducts

Bromomagnesium ureide-carbon dioxide adducts, models of the carboxylated biotin complex, undergo caboxylation of a variety of carbonyl compounds in good yield.