Akihiro Yokoyama

Precision synthesis of poly(3-hexylthiophene) from catalyst-transfer Suzuki-Miyaura coupling polymerization.

(t)Bu(3) PPd(Ph)Br (1)-catalyzed Suzuki-Miyaura coupling polymerization of 2-(4-hexyl-5-iodo-2-thienyl)-4,4,5,5-tetramethyl-1,3,2-dioxaborolane (2) was investigated. Monomer 2 was polymerized with 1 at 0u2009°C in the presence of CsF and 18-crown-6 in THF containing a small amount of water to yield P3HT with a narrow molecular weight distribution and almost perfect head-to-tail regioregularity. The M(n) values increased up to 11,400 gu2009·u2009mol(-1) in proportion to the feed ratio of 2 to 1. The MALDI-TOF mass spectra showed that P3HT with moderate molecular weight uniformly had a phenyl group at one end and a hydrogen atom at the other, indicating involvement of a catalyst-transfer mechanism. Successive 1-catalyzed polymerization of fluorene monomer 3 and then 2 yielded a well-defined block copolymer of polyfluorene and P3HT.

Oxovanadium complexes with quinoline and pyridinone ligands: syntheses of the complexes and effect of alkyl chains on their apoptosis-inducing activity in leukemia cells.

Vanadium complexes with quinoline ligands (1b-g) and pyridinone ligands (2b-d) were synthesized, and the effect of the length and shape of alkyl chains on the antiproliferative activity toward U937 cells was studied. For the synthesis of the vanadium complexes, quinoline and pyridinone ligands were prepared and then treated with VOSO(4) or VO(acac)(2). The vanadyl(IV) complexes were characterized by IR, ESR, and UV-vis spectroscopy and elemental analyses. The antiproliferative activity of 1a-g toward U937 cells showed little dependence on the length and shape of the alkyl chain. In contrast, a good correlation was found between the IC(50) values and partition coefficients (logP) values of 2a-c. Among them, 2c showed the highest inhibitory activity, and its IC(50) value was smaller than that of cisplatin. The apoptosis-inducing ability of 2b and 2c was supported by annexin V-propidium iodide staining experiments and agarose gel electrophoresis analysis. Inhibitors of caspase-3, -8, and -9 did not affect the antiproliferative activity of 2c, indicating that the apoptosis induced by 2c was via a caspase-independent pathway.

Synthesis and antimicrobial activity of 2,3-bis(bromomethyl)quinoxaline derivatives

We synthesized 12 derivatives of 2,3-bis(bromomethyl)quinoxaline with substituents at the 6- and/or 7-positions, and evaluated their activities against bacteria and fungi. Of the 12 compounds, nine (1a-h, 1j, and 1k) showed antibacterial activity. The derivative 1g, which bears a trifluoromethyl group at the 6-position, showed the highest activity against Gram-positive bacteria, while 1c, which has a fluoro-group at the 6-position, showed the widest antifungal activity spectrum. However, only the derivative with an ethyl ester substitution, 1k showed activity against Gram-negative bacteria.

Conformational and Optical Characteristics of Unidirectionally Twisted Binaphthyl-Bipyridyl Cyclic Dyads

An axially chiral binaphthyl-bipyridyl cyclic dyad in which the two units are connected by short -CH2O- linkers was synthesized. Experimental and theoretical analyses indicate that the (R)-binaphthyl unit in the dyad induces (R)-chirality in the bipyridyl unit, both in the solid state and in solution. It is shown that vibrational circular dichroism (VCD) is useful to determine the twisting pattern of 2,2-bipyridyl compounds. The dyad shows crystallization-induced emission enhancement (CIEE).

Intramolecular [2+2] Photocycloaddition and Cycloreversion of Ferulic Acid Derivatives

ABSTRACT : Intramolecular photocycloaddition of ferulic acid derivatives proceeded in high yields to give head-to-head intramolecular photodimers as three atropisomers. The photocycloaddition was sensitized by triplet sensitizers such as benzophenone, whereas photocycloreversion was promoted by 9,10-dicyanoanthracene (DCA) as an electron-transfer photocatalyst. On the other hand, intermolecular photocycloaddition afforded a head-to-tail photodimer. Scheme 1 Recently, much attention has been focused on the chemical and biological properties of ferulic acid derivatives including the anti-carcinogenesis and the anti-oxidation. 1 We have recently found a convenient method for the mass production of ferulic acid from the oily component of rice bran, which contribute to the eco chemistry. 2 Ferulic acid ( 1 ) and its derivatives are expected to be photochemically reactive, because the inter- and intra-molecular photocycloaddition of cinnamic acid and its derivatives have been widely investigated from the synthetic and mechanistic viewpoints. The topochemical intermolecular photocyclodimerization of cinnamic acid in solid states,