716-76-7Relevant articles and documents
Characterization of chemo- and regioselectivity in enzyme-catalyzed consecutive hydrolytic deprotection of methyl acetyl derivatives of 1-β-O-acyl glucuronides
Baba, Akiko,Yoshioka, Tadao
experimental part, p. 74 - 82 (2011/12/22)
Methyl acetyl derivatives of 1-β-O-(o-, m-, or p-phenyl)benzoyl glucuronides 2a-c are fully deprotected by a one-pot consecutive enzyme-catalyzed hydrolytic reaction to afford 4a-c, without isolation of the O-deacetylated derivatives 3a-c. A lipase AS Amano from Aspergillus niger (LAS) and a carboxylesterase from Streptomyces rochei (CSR) showed high chemoselectivity toward the O-deacetylation of the o- and m-isomers, respectively. Chemoselective O-deacetylation of the p-isomer was promoted only in the presence of both enzymes. A lipase type B from Candida antarctica (CALB) was effective for the subsequent enzymatic hydrolysis of the methyl esters of 3a-c. LAS exhibited also regioselective 3-O-deacetylation activity to afford the corresponding 2,4-di-O-acetyl intermediates 5a-c, for which CSR showed higher O-deacetylation activity than that for 2a-c. In kinetic studies using p-nitrophenyl ester substrates, LAS exhibited a broader acyl preference, the octanoyl ester being most effectively hydrolysed, whereas CSR exhibited the highest hydrolytic activity toward the acetyl ester. LAS and CSR play complementary as well as synergistic roles in the O-deacetylation of 2 bearing R groups of different steric bulkiness.
Generation of Polyphenylene Radical Cations and Their Cosensitization Ability in the 9,10-Dicyanoanthracene-Sensitized Photochemical Chain Reactions of 1,2-Bis(4-methoxyphenyl)cyclopropane
Tamai, Toshiyuki,Ichinose, Nobuyuki,Tanaka, Tomoko,Sasuga, Tsuneo,Hashida, Isao,Mizuno, Kazuhiko
, p. 3204 - 3212 (2007/10/03)
Cosensitization effects of polyphenylene compounds (PP) such as biphenyl (BP), terphenyls (o-, m-, p-TP), and phenanthrene (Phen) in photoinduced electron-transfer reactions were examined. The 9,10-dicyanoanthracene (DCA)-sensitized cis-trans photoisomerization of 1,2-bis(4-methoxyphenyl)-cyclopropane (CP), which proceeds in a chain reaction via free radical cation of CP (CP.+) as a chain carrier, was accelerated by adding PP, particularly by TP. A similar accelerating effect was observed in the DCA-sensitized photooxygenation of CP as another example. BP and TP were more stable under the oxygenation condition than phenanthrene and naphthalene, which also accelerate the photooxygenation CP. CP.+ is generated by the direct electron transfer from CP to the excited singlet state of DCA (1DCA*) and also by the secondary electron transfer from CP to PP.+, which is generated by the primary electron transfer from PP to 1DCA*. The laser flash photolysis study revealed that the quantum yield for the formation of free CP.+ in the direct electron transfer from CP to 1DCA* (ΦCP.+ ≈ 0.1) was smaller than that in the presence of PP. This is due to the high yield of free PP.+ generation by the primary electron transfer and the efficient secondary electron transfer from CP to PP.+. The secondary electron transfers were found to take place in nearly diffusion-controlled rates (0.9-1.5 × 1010 M-1 s-1). The high yield of PP.+ as free radical ions does not seem to be the sole factor of the cosensitization of PP for the DCA-sensitized photoreactions of CP. The ratio of the quantum yields of the photoreactions to that of the initial CP.+ formation (turnover) also increased by the addition of PP from 3 (isomerization) and 15 (oxygenation) to 32-90 for both reactions. The second-order rate constant for the decay of CP.+ in aerated acetonitrile was decreased by a factor of 0.5-0.8 by the addition of PP. We concluded that the cosensitization effect in the photoreaction involves a π-complex formation between CP.+ and PP assisting the chain reaction as well as initial CP.+ formation.
ELECTRON-TRANSFER MEDIATED PHOTOOXYGENATION OF BIPHENYL AND ITS DERIVATIVES IN THE PRESENCE OF Mg(ClO4)2
Mizuno, Kazuhiko,Ichinose, Nobuyuki,Tamai, Toshiyuki,Otsuji, Yoshio
, p. 5823 - 5826 (2007/10/02)
The 9,10-dicyanoanthracene-sensitized photooxygenation of biphenyl and its derivatives in the presence of Mg(ClO4)2 in acetonitrile brought about the oxidative cleavage of benzene nucleus to give benzoic acid and its derivatives.
