共查询到20条相似文献,搜索用时 15 毫秒
1.
Nanoparticles of (R)-1,1′-bi-2-naphthol dibenzoate (R-BND) ranging from 40 to 170 nm were prepared by using the reprecipitation method. The nanoparticles exhibit size-dependent exciton chirality, where the coupling potential V12 of 1Bb transitions increases as nanoparticles grow and simultaneously the exciton chirality peaks exhibit the bathochromic shift. Such size-dependent optical properties can be attributed to the lattice hardening with increased particle size, which leads to a decreased dihedral angel θ between the two naphthyl planes in a R-BND molecule. 相似文献
2.
Xiao D Yang W Yao J Xi L Yang X Shuai Z 《Journal of the American Chemical Society》2004,126(47):15439-15444
Organic nanoparticles from a chiral auxiliary, (R)-(+)-1,1'-bi-2-naphthol dimethyl ether (BNDE), with a range of particle sizes from 25 to 100 nm were fabricated through the reprecipitation method. It is found that BNDE nanoparticles exhibit positive exciton chirality in 200-260 nm region in circular dichroism (CD) spectra, which are completely opposite to CD spectra of the dilute solution. The exciton chirality of the particles displays size-dependent behavior; that is, the exciton chirality peaks evolve to the low-energy side with increase in particles size. CD spectra accompanied with UV, fluorescence spectra, lifetime measurements of the excited states, and quantum mechanical calculations reveal that the chirality inversion results from intermolecular exciton coupling between two adjacent BNDE molecules in the nanoparticles, and the bathochromic shift of the peaks is attributed to the increased intermolecular interaction with increasing particle size. 相似文献
3.
Jingjin Chen Andrew J. Ferreira Christopher M. Beaudry 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(44):12125-12128
Bis(indole) alkaloids from Arundo donax were synthesized using the first ynindole Diels–Alder reaction. The alkaloids are chiral, having stable enantiomeric conformations with half‐lives of racemization of t1/2=4150–25100 seconds at room temperature. Their absolute stereochemistry was determined using the exciton chirality method. 相似文献
4.
Synthesis of Bis(indole) Alkaloids from Arundo donax: The Ynindole Diels–Alder Reaction,Conformational Chirality,and Absolute Stereochemistry 下载免费PDF全文
Dr. Jingjin Chen Andrew J. Ferreira Prof. Dr. Christopher M. Beaudry 《Angewandte Chemie (International ed. in English)》2014,53(44):11931-11934
Bis(indole) alkaloids from Arundo donax were synthesized using the first ynindole Diels–Alder reaction. The alkaloids are chiral, having stable enantiomeric conformations with half‐lives of racemization of t1/2=4150–25100 seconds at room temperature. Their absolute stereochemistry was determined using the exciton chirality method. 相似文献
5.
《中国化学》2018,36(2):124-128
Three limonoids cipaferoids A–C ( 1 – 3 ) representing two different scaffolds were isolated from Cipadessa baccifera. Their structures were completely assigned by spectroscopic data, CD exciton chirality method, and X‐ray crystallography. Compounds 2 and 3 exhibited moderate antimalarial activity with IC50 values of 9.3±0.1 and 14.7±4.8 μmol•L–1, respectively. 相似文献
6.
Features of electronic circular dichroism and tips for its use in determining absolute configuration
Jesús T. Vázquez 《Tetrahedron: Asymmetry》2017,28(10):1199-1211
This review focuses on the general features of electronic circular dichroism (ECD) as applied in determining the absolute configuration of organic compounds. The high sensitivity and straightforward spectral interpretation of the exciton chirality method makes this approach very useful, and complementary to X-ray crystallography. A brief tutorial is provided on ECD, with precautions and tips for using it, especially the exciton chirality method. The spectroscopic ECD of several examples are analyzed. 相似文献
7.
Two novel stereoisomeric analogues of 1,25-dihydroxyvitamin D3 bearing a spiro-oxetane at the C3 position of the A-ring have been designed and synthesized in a convergent manner. The absolute configuration at the C1 position of the synthesized compounds was determined by the circular dichroism exciton chirality method using the corresponding C1-allylic benzoates. The replacement of the C3-hydroxy group with a spiro-oxetane provided an advantageous conformational preference for the parent seco-steroids, which would facilitate the formation of a stable receptor complex. 相似文献
8.
Katumitu Hayakawa Mayuko Sato Izumi Nagata Naoya Yamato Hiroshi Murata Masaru Tanokura 《Colloid and polymer science》2006,284(12):1453-1458
Circular dichroism (CD) and absorption spectra were measured for acridine orange derivatives: 3,6-bis(dimethylamino) acridine (AO), 3,6-bis(dimethylamino)-10-methylacridinium bromide (C1AO), and 3,6-bis(dimethylamino)-10-dodecylacridinium bromide (C12AO) in aqueous dodecanoyl-l-threonine (C12Thr) solutions at 30, 40, 50, and 60 °C and pH 8–9. CD spectra were not induced for AO and C1AO in C12Thr aqueous solutions. Induced circular dichroism (ICD) based on the exciton interaction was found for premicellar aggregates of C12AO with C12Thr, but the micellar aggregates failed to induce CD for solubilized C12AO at a higher concentration than C12Thr critical micelle concentration. The maximum ICD intensity was observed for 1:1.2 aggregates of C12AO and C12Thr. The ICD spectrum indicated positive chirality at 30 °C, but negative chirality at 50 °C. The chirality transition occurred at 40∼45 °C. The slow change in both the absorption and ICD spectra is ascribed partly to the rearrangement of dye alignment and partly to the growth of the aggregate; the system reaches final phase separation after a few days. 相似文献
9.
Xing Su Xiangkun Li Hongxun Tao Jinge Zhou Tao Wu Guixin Chou Zhihong Cheng 《Journal of separation science》2013,36(21-22):3644-3650
A combinative method using overpressured layer chromatography (OPLC) and TLC bioautography against O2?? was developed to separate antioxidants from Glehnia littoralis roots. Through target‐directed isolation by the TLC bioautographic method, seven compounds including five antioxidants were rapidly isolated by OPLC and identified as 1‐linoloyl‐3‐palmitoylglycerol, facarindiol, panaxynol, isoimperatorin, β‐sitosterol, scopoletin, and umbelliferone from G. littoralis roots. This OPLC method is a very suitable separation technique for light‐sensitive polyacetylenes (panaxynol and facarindiol) with higher isolated yields compared to conventional open column chromatography. This is the first report on the separation of polyacetylenes by OPLC. 相似文献
10.
Richard C. Jennings 《Tetrahedron letters》1982,23(26):2693-2696
All four stereoisomers of precocene I 3,4-dihydrodiol have been prepared and their absolute configurations assigned by the exciton chirality method. 相似文献
11.
Absolute configuration of (?)-solanapyrone A was confirmed by the application of CD exciton chirality method to the dibenzoate derivative. 相似文献
12.
Shohei Nishitani Prof. Dr. Ryo Sekiya Prof. Dr. Takeharu Haino 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(2):679-683
The development of chiral nanographenes has mostly been carried out by bottom-up methods and examples of species developed by the post-modification of nanographenes prepared by top-down methods remain limited. We show that the attachment of chiral functional groups onto the edge of nanographenes generates chirality on the surface. X-ray diffraction analysis and DFT calculations indicate that the chirality of the functional groups is transferred to the surface via steric interactions from the chiral center through the five-membered cyclic imide to the nanographene edge. The exciton coupling between the p-bromophenyl groups confirms that the functional groups are arranged on the armchair edges at distances that permit exciton coupling, which provides information about their relative orientation. These pieces of information help to elucidate the edge structure of nanographenes prepared by top-down methods. 相似文献
13.
Tetracosanaphthalenes with diethylaminocarbonylmethoxy side chains were constructed by bottom-up synthesis, and their absolute configurations were determined by an exciton chirality method. 相似文献
14.
《Tetrahedron: Asymmetry》1998,9(9):1549-1556
Fumonisins are mycotoxins produced by Fusarium moniliforme (Sheldon) and other related fungi that are common contaminants of corn and other grains throughout the world. The circular dichroism (CD) exciton chirality method was applied to determine the absolute configuration of the terminal part of the backbone of fumonisins. Using the p-dimethylaminobenzoate chromophore, the structure of FB1 was confirmed to be 2S, 3S and 5R, while that of FB3 is described for the first time to be 2S and 3S. 相似文献
15.
Shohei Nishitani Ryo Sekiya Takeharu Haino 《Angewandte Chemie (International ed. in English)》2020,59(2):669-673
The development of chiral nanographenes has mostly been carried out by bottom‐up methods and examples of species developed by the post‐modification of nanographenes prepared by top‐down methods remain limited. We show that the attachment of chiral functional groups onto the edge of nanographenes generates chirality on the surface. X‐ray diffraction analysis and DFT calculations indicate that the chirality of the functional groups is transferred to the surface via steric interactions from the chiral center through the five‐membered cyclic imide to the nanographene edge. The exciton coupling between the p‐bromophenyl groups confirms that the functional groups are arranged on the armchair edges at distances that permit exciton coupling, which provides information about their relative orientation. These pieces of information help to elucidate the edge structure of nanographenes prepared by top‐down methods. 相似文献
16.
A new one-step strategy is described for the stereochemical assignment of acyclic 2- and 3-sulfanyl-1-alkanols using the CD exciton chirality method. Using the 9-anthroate chromophore for the derivatization of both functional groups, the resulting bisignate CD curves unequivocally allow the determination of the stereochemistry from a single CD measurement. The usefulness of the new method is demonstrated using synthesized optically pure 3-sulfanyl-1-hexanols and 2-sulfanyl-1-hexanols as model compounds. The developed microscale method is also useful for the stereochemical assignment of 1,2- and 1,3-diols. To our knowledge this is the first application of the CD exciton chirality method to acyclic 2- and 3-sulfanyl-1-alkanols. 相似文献
17.
18.
包公藤甲素及其类似物的绝对构型研究 总被引:4,自引:0,他引:4
本文采用Pr(dpm)3诱导CD裂分Cotton效应法、激子手性法和Horean法对新缩瞳剂包公藤甲素(1)及其类似物包公藤丙素(2)、凹脉丁公藤碱(3)及两者的N-甲基化物(4、5)进行了研究。确定了它们的绝对构型分别为: (2S, 6S)2β-羟基-6β-乙酰氧基去甲莨菪烷、(2S, 6S)-2β, -6β-二羟基去甲莨菪烷、(2S,7R)-2β, 7β-二羟基去甲莨菪烷、(2S, 6S)-2β, 6β-二羟基莨菪烷和(2S, 7R)-2β, 7β-二羟基莨菪烷。通过构象分析和用绝对构型已知的化合物验证, 初步解释了Horeau法的测定结果。 相似文献
19.
Lintuluoto JM Nakayama K Setsune J 《Chemical communications (Cambridge, England)》2006,(33):3492-3494
Octaphyrin O1 has been found to be an effective sensor for the direct determination of absolute configuration of a variety of carboxylic acids at mM concentrations at room temperature based on CD exciton chirality method. 相似文献
20.
Tsubaki K 《Organic & biomolecular chemistry》2007,5(14):2179-2188
Helical oligonaphthalenes were constructed by bottom-up synthesis (repeating dimerization reactions), their absolute configurations were determined by an exciton chirality method and their functions, such as energy transfer, are also reported. 相似文献