The catalytic systems composed of ionic liquids containing BF 4 -anion and HBF 4 showed high catalytic activity to produce 4-methyl-2,4-diphenyl-1-pentene (MDP-1) or 1,1,3-trimethyl-3-phenylindan (TPI) under different temperature conditions. Up to 90.8% selectivity to MDP-1 with a 98.7% conversion of a-methylstyrene was obtained at 60°C in the presence of [HexMIm]BF 4 -HBF 4 , while exclusive TPI was yielded when the reaction temperature increased to 120°C. Further studies showed that another ionic liquid, [BMIm]Cl Á 2AlCl 3 , could act as an excellent catalyst and solvent for the dimerization of a-methylstyrene to produce TPI. The dimerization of a-methylstyrene catalyzed by [HexMIm]BF 4 -HBF 4 and [BMIm]Cl Á 2AlCl 3 performed the same reaction mechanism and the proton was the active species.
The secondary structure of a new type of recombinant RGD-hirudin, which has the activities of anti-thrombin and anti-platelet aggregation, has been studied by Fourier transform infrared spectroscopy (FT-IR), Raman spectroscopy and circular dichroism (CD) methods. The distribution of various secondary structure elements was determined using only a very small amount of sample protein. It was found that the recombinant RGD-hirudin contains about 26% extended chain, 21% beta-turn and 53% unordered structure, leaving no alpha-helix. The results showed that the regular secondary structure of recombinant RGD-hirudin is increased compared with wild-type hirudin. The RGD segment that is located at the end of a long arm of a beta-sheet is thought to play an important role in the additional function of anti-platelet aggregation. Throughout the experiments, FT-IR, Raman spectroscopy and CD generated mutually reinforcing results.
Abstract:The room temperature ionic liquid [bmim] [PF 6 ] was employed as the reaction medium in the asymmetric glyoxylate-ene reaction of α-methyl styrene (4a) with ethyl glyoxylate using chiral palladium(II) complexes as the catalysts. [Pd(S-BINAP)(3,5-CF 3 -PhCN) 2 ](SbF 6 ) 2 (1b) showed the highest catalytic activity. Under the reaction conditions of 40 o C, 0.5 h, and 1b/4a molar ratio of 0.05, ethyl α-hydroxy-4-phenyl-4-pentenoate was obtained in excellent chemical yield (94 %) with high enantioselectivity (70 %). Other α-hydroxy esters can also be obtained in high chemical yields and enantioselectities through the glyoxylate-ene reactions of alkenes with glyoxylates catalyzed by 1b in [bmim] [PF 6 ]. Moreover, the ionic liquid [bmim] [PF 6 ] which contained the palladium(II) complex could be recycled and reused several times without significant loss of the catalytic activity.
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