20570-70-1Relevant articles and documents
New open-chain tetrapyrroles as chromophores in the plant photoreceptor phytochrome
Robben, Uwe,Lindner, Ingo,Gaertner, Wolfgang
, p. 11303 - 11311 (2008)
A series of six open-chain tetrapyrroles has been synthesized and used as chromophores for the plant photoreceptor protein phytochrome. The novel chromophores vary in the size of substituents 17 and 18 at ring D. This ring undergoes maximal conformational change upon light excitation (Z → E photoisomerization of the 15,16-double bond). Instead of methyl and vinyl substituents (positions 17, 18) as present in the native chromophore phytochromobilin, dimethyl, methyl and isopropyl, methyl and tert-butyl, ethyl and methyl, vinyl and methyl, and isopropyl and methyl substituents have been generated. All novel chromophores assemble with the apoprotein. The obtained chromoproteins show hypsochromic shifts of the absorbance maxima by 10 nm maximally, compared to the native pigment, except for the 17-isopropyl-18- methyl-substituted compound which showed a 100 nm hypsochromic shift of selectively the Pr form. The assembly kinetics were slowed down in correlation to the increasing size of the substituents, with stronger effects for modified substituents at position 17. The thermal stability of the photoinduced Pfr form for the 18-isopropyl and the 18-tert butyl substituents was even greater than that of the native pigments. Those chromophores carrying substituents at position 17 larger than the methyl group (ethyl and isopropyl) showed a very low stability of the respective P fr forms. Time-resolved detection of the Pfr to Pfr conversion (laser-induced flash photolysis) revealed a slower formation of the Pfr form for those chromophores carrying larger substituents at position 18, whereas the rise and decay kinetics of the early intermediates are only moderately changed. Introduction of larger substituents at position 17 (ethyl, vinyl, and isopropyl) causes drastic changes in the kinetics; in particular the formation of the first thermally stable intermediate, I 700, is significantly slowed, making a detection of its rise possible.
Asymmetric Syn-selective Henry reaction catalyzed by the sulfonyldiamine-CuCl-pyridine system
Arai, Takayoshi,Takashita, Ryuta,Endo, Yoko,Watanabe, Masahiko,Yanagisawa, Akira
, p. 4903 - 4906 (2008/12/20)
(Chemical Equation Presented) A catalytic asymmetric Henry reaction has been developed with use of a sulfonyldiamine-CuCl complex as a catalyst. A series of new binaphthyl-containing sulfonyldiamine ligands (2a-h) were readily synthesized in two steps starting from commercially available chiral 1,2-diamines. The (R,R)-diamine-(R)-binaphthyl ligand (2d)-CuCl complex smoothly catalyzed the enantioselective Henry reaction with the assistance of pyridine to give the corresponding adduct with high enantiomeric excess (up to 93%). Moreover, the 2d-CuCl-pyridine system promotes the diastereoselective Henry reaction in syn-selective manner to give the adduct in up to 99% yield with 92:8 synlanti selectivity. The enantiomeric excess of the syn-adduct was 84% ee.
Use of heterogeneous catalyst KG-60-NEt2 in Michael and Henry reactions involving nitroalkanes
Ballini, Roberto,Bosica, Giovanna,Livi, Damiana,Palmieri, Alessandro,Maggi, Raimondo,Sartori, Giovanni
, p. 2271 - 2273 (2007/10/03)
The N,N-diethylpropylamine supported on amorphous silica (KG-60-NEt2) catalyses the formation of carbon-carbon bonds by nitroalkanes through both the nitroaldol (Henry) and Michael reactions. The catalyst shows general utility with a variety of electrophilic acceptors. Moreover, the catalyst can be reused for two further cycles without loss of the activity.
