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1.
Summary Optically pure (+)-beta-eudesmol is a possible starting material for the synthesis of several termite defense compounds. A
two step procedure for the isolation of gram quantities of (+)-beta-eudesmol from commercially availableAmyris balsamifera oil (syn. West Indian sandalwood oil), containing 8% beta-eudesmol, was developed. Step one consisted of an efficient vacuum
distillation of the total oil. Step two was a medium pressure LC separation with an AgNO3 impregnated silica gel stationary phase. Several other separation procedures failed due to the presence of many closely related
sesquiterpene alcohols (75% of the oil). 相似文献
2.
Makoto Obata Ryo Asato Kazunori Mitsuo Shiho Hirohara 《Journal of polymer science. Part A, Polymer chemistry》2014,52(7):963-972
Three CF3‐substituted methyl methacrylates (MMAs), 2,2,2‐trifluoroethyl methacrylate (TFEMA), 1,1,1,3,3,3‐hexafluoroisopropyl methacrylate (HFIPMA) and nonafluoro‐tert‐butyl methacrylate (NFTBMA), were polymerized by conventional radical polymerization to give oxygen‐permeable polymers for application in pressure‐sensitive paint (PSP). The radical copolymerizations of styrene with TFEMA, HFIPMA, or NFTBMA were carried out to examine the effect of CF3 groups on the polymerizability. The e values increased in the order of MMA (0.40) < TFEMA (0.76) < HFIPMA (1.19) < NFTBMA (1.31). The homopolymers of TFEMA, HFIPMA and NFTBMA (PTFEMA, PHFIPMA, and PNFTBM, respectively) were examined as polymers for use in PSP using 5,10,15,20‐tetrakis(pentafluorophenyl)porphinato platinum(II) (PtTFPP). The PSP consisting of PNFTBMA and PtTFPP exerted very high pressure sensitivity and very low temperature sensitivity. In the absence of oxygen, the temperature sensitivity decreased in the order of PTFEMA > PHFIPMA > PNFTBMA = PMMA, which corresponds to the order of glass transition temperatures (Tg). However, the activation energies of the overall process of the luminescence quenching by oxygen were found to be 16.8 (PMMA), 13.0 (PTFEMA), 6.8 (PHFIPMA), and 4.3 kJ mol?1 (PNFTBMA). Therefore, the low temperature sensitivity of PNFTBMA was attributed to its high degree of substitution with CF3 groups and to its relatively high Tg value. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 963–972 相似文献
3.
Symmetrically substituted styrenes photochemically gave unstable conformers in low temperature organic glass in a manner consistent with the recently postulated Hula-twist mechanism of photoisomerization. 相似文献
4.
[structure: see text] Experimental and calculated data show that the relative energy levels of the two lowest excited states of azulene are sensitive to the nature and position of substituents on the nonalternant hydrocarbon. Extending such investigations led to a rational explanation for some of the baffling data on azulenic bacteriorhodopsin analogues in the literature. 相似文献
5.
6.
Hiroyuki Matsumoto Aravinda Kini Alfred E. Asato Marlene Denny Allen Kropf Willem J. DeGrip 《Tetrahedron》1984,40(3):473-482
Results of interaction of seven new geometric isomers of retinal (7-cis, 7,9-dicis; 7,11-dicis, 7,13-dicis; 9,11-dicis 7,9,11-tricis 7,9,13-tricis) with bovine opsin are reported. All of them form pigments with absorption maxima varying between 450 and 480 nm. The rates of pigment formation were generally considerably lower than those of 11-cis-retinal and the yields were less than quantitative. Implications of these results for the stereospecificity of the binding site of opsin are discussed. 相似文献
7.
R. S. H. Liu Erik Krogh Xiao-Yuan Li Dennis Mead L. U. Colmenares J. R. Thiel Jeannette Ellis Darren Wong A. E. Asato 《Photochemistry and photobiology》1993,58(5):701-705
Prompted by the near infrared-absorbing properties of some of the azulenic bacteriorhodopsin (bR) analogs, we have analyzed their absorption characteristics along with 11 new related ring-fused analogs and the corresponding Schiff bases (SB) and protonated Schiff bases (PSB). The following three factors are believed to contribute to the total red shift of each of the pigment analogs (αRS): perturbation of the basic chromophore (SB shift, ΔSB), protonation of the SB (PSB shift, PSBS) and protein perturbation (the opsin shift, OS). For each factor, effects of structural modifications were examined. For the red-shifted pigments, percent OS has been suggested as an alternate way of measuring protein perturbation. Computer-simulated chromophores provided evidence against any explanation involving altered shapes of the binding pocket as a major cause for absorption differences. Implications of the current bR results on preparation of further red-shifted bR and possible application to visual pigment analogs are discussed. 相似文献
8.
9.
[reaction: see text] A rhodium complex coordinated with (S,S)-2,5-dibenzylbicyclo[2.2.2]octa-2,5-diene (Bn-bod) showed high catalytic activity and high enantioselectivity in the asymmetric 1,4-addition of arylboroxines to cyclic alpha,beta-unsaturated ketones, 0.005-0.01 mol % of the catalyst giving high yields of the addition products with not lower than 94% ee. The turnover frequency of the catalyst is up to 1.4 x 10(4) h(-1). 相似文献
10.
[reaction: see text] New axially chiral 2,2'-bipyridine N,N'-dioxides were obtained by a new method that does not involve any procedures for the separation of enantiomers. One of the dioxides, (R)-3,3'-bis(hydroxymethyl)-6,6'-diphenyl-2,2'-bipyridine N,N'-dioxide, exhibited extremely high catalytic activity for the asymmetric allylation of aldehydes with allyl(trichloro)silane. The allylation of aromatic aldehydes proceeded in the presence of 0.01 or 0.1 mol % of the dioxide catalyst to give the corresponding homoallyl alcohols of up to 98% ee. 相似文献