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991.
992.
Calophyline A (1), a novel unprecedented rearranged monoterpenoid indole alkaloid, along with a new natural product N-methyl aspidodasycarpine (2) and six known analogues, was isolated from the trunk barks of Winchia calophylla. The structure of compound 1 was elucidated on the basis of spectroscopic data and then confirmed by a single-crystal X-ray crystallographic analysis. A hypothetical biogenetic pathway for compound 1 was proposed. All isolated compounds were evaluated for their in vitro cytotoxicity against a small panel of human cancer cell lines. 相似文献
993.
A furantaxane (4) with an unusual 6/8/6/5 ring system and two hydroxylated products (2, 3) were isolated following the biotransformation of a taxane (1) by Streptomyces griseus. The structures of the isolates were elucidated by spectroscopic analysis. The absolute configuration of 4, which exhibited potent reversal activity in the A549/taxol MDR tumor cell line, was unambiguously deduced by single-crystal X-ray diffraction. 相似文献
994.
995.
Liu F Willhammar T Wang L Zhu L Sun Q Meng X Carrillo-Cabrera W Zou X Xiao FS 《Journal of the American Chemical Society》2012,134(10):4557-4560
The relatively small and sole micropores in zeolite catalysts strongly influence the mass transfer and catalytic conversion of bulky molecules. We report here aluminosilicate zeolite ZSM-5 single crystals with b-axis-aligned mesopores, synthesized using a designed cationicamphiphilic copolymer as a mesoscale template. This sample exhibits excellent hydrothermal stability. The orientation of the mesopores was confirmed by scanning and transmission electron microscopy. More importantly, the b-axis-aligned mesoporous ZSM-5 shows much higher catalytic activities for bulky substrate conversion than conventional ZSM-5 and ZSM-5 with randomly oriented mesopores. The combination of good hydrothermal stability with high activities is important for design of novel zeolite catalysts. The b-axis-aligned mesoporous ZSM-5 reported here shows great potential for industrial applications. 相似文献
996.
Wu F Zhu H Sun L Rajendran C Wang M Ren X Panjikar S Cherkasov A Zou H Stöckigt J 《Journal of the American Chemical Society》2012,134(3):1498-1500
The Pictet-Spenglerase strictosidine synthase (STR1) has been recognized as a key enzyme in the biosynthesis of some 2000 indole alkaloids in plants, some with high therapeutic value. In this study, a novel function of STR1 has been detected which allows for the first time a simple enzymatic synthesis of the strictosidine analogue 3 harboring the piperazino[1,2-a]indole (PI) scaffold and to switch from the common tryptoline (hydrogenated carboline) to the rare PI skeleton. Insight into the reaction is provided by X-ray crystal analysis and modeling of STR1 ligand complexes. STR1 presently provides exclusively access to 3 and can act as a source to generate by chemoenzymatic approaches libraries of this novel class of alkaloids which may have new biological activities. Synthetic or natural monoterpenoid alkaloids with the PI core have not been reported before. 相似文献
997.
Moliner M Willhammar T Wan W González J Rey F Jorda JL Zou X Corma A 《Journal of the American Chemical Society》2012,134(14):6473-6478
A new molecular sieve, ITQ-38, containing interconnected large and medium pores in its structure has been synthesized. The rational combination of dicationic piperidine-derivative molecules as organic structure directing agents (OSDAs) with germanium and boron atoms in alkaline media has allowed the synthesis of ITQ-38 zeolite. High-resolution transmission electron microscopy (HRTEM) has been used to elucidate the framework topology of ITQ-38, revealing the presence of domains of perfect ITQ-38 crystals as well as very small areas containing nanosized ITQ-38/ITQ-22 intergrowths. The structure of ITQ-38 is highly related to ITQ-22 and the recently described polymorph C of ITQ-39 zeolite. It shares a common building layer with ITQ-22 and contains the same building unit as the polymorph C of ITQ-39. All three structures present similar framework density, 16.1 T atoms/1000 ?(3). 相似文献
998.
A novel electrochemical biosensing strategy based on a three-dimensional fishnet of DNA-linked nanoparticle supramolecular structure triggered by the analyst for detection of Hg(2+) has been designed. The detection limit is 7.38 pM and the sensor's selectivity and facility have been significantly improved. 相似文献
999.
通过乙烯基乙醚和连苯三酚缩二乙烯基苯树脂( PDVB resin)的羟基加成,合成了具有缩醛结构的活性醚化物,并对该活性醚化物的合成条件进行优化.这种具有缩醛结构的活性醚化物具有常温酸解和热解性能,作为阻溶促溶剂可用于常温化学增幅阳图感光成像和阳图热敏成像中.用于阳图热敏CTP感热成像配方中,使得版材具有高感度、高抗碱性、高稳定性;用于阳图CTcP感光成像配方中,使得该版材的综合成像性能优良;用于正性光致抗蚀剂成像配方中,使得该正性光致抗蚀剂具有高感度和高分辨率. 相似文献
1000.
通过熔融共混法制备了一系列聚乳酸(PLA)/矿物填料复合材料.采用示差扫描量热(DSC)研究了含有碳酸钙(CaCO3)、蒙脱土(MMT)和凹凸棒土(AT)的聚乳酸复合材料在不同热历程中的结晶和熔融行为.研究发现,MMT和AT对PLA的慢速降温结晶无明显影响,而碳酸钙在慢速降温过程中能够有效促进PLA结晶;在2.5 K/min的降温速率下,结晶热焓随碳酸钙含量增加而增加;填料种类和含量会对复合材料升温过程的冷结晶和熔融产生较大影响,低含量矿物填料主要对PLA的冷结晶起成核作用,其中MMT成核效果最好.较高含量下不同填料会对PLA晶体形态产生影响,从而得到多样的DSC曲线变化. 相似文献