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1.
Nucleophile‐Dependent Regio‐ and Stereoselective Ring Opening of 1‐Azoniabicyclo[3.1.0]hexane Tosylate 下载免费PDF全文
Mi‐Kyung Ji Dietmar Hertsen Doo‐Ha Yoon Heesung Eum Hannelore Goossens Prof. Dr. Michel Waroquier Prof. Dr. Veronique Van Speybroeck Prof. Dr. Matthias D'hooghe Prof. Dr. Norbert De Kimpe Prof. Dr. Hyun‐Joon Ha 《化学:亚洲杂志》2014,9(4):1060-1067
1‐[(1R)‐(1‐Phenylethyl)]‐1‐azoniabicyclo[3.1.0]hexane tosylate was generated as a stable bicyclic aziridinium salt from the corresponding 2‐(3‐hydroxypropyl)aziridine upon reaction with p‐toluenesulfonyl anhydride. This bicyclic aziridinium ion was then treated with various nucleophiles including halides, azide, acetate, and cyanide in CH3CN to afford either piperidines or pyrrolidines through regio‐ and stereoselective ring opening, mediated by the characteristics of the applied nucleophile. On the basis of DFT calculations, ring‐opening reactions under thermodynamic control yield piperidines, whereas reactions under kinetic control can yield both piperidines and pyrrolidines depending on the activation energies for both pathways. 相似文献
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RD Harris WS Baker Van Stipdonk MJ RM Crooks EA Schweikert 《Rapid communications in mass spectrometry : RCM》1999,13(14):1374-1380
A suite of keV polyatomic or 'cluster' projectiles was used to bombard unoxidized and oxidized self-assembled monolayer surfaces. Negative secondary ion yields, collected at the limit of single ion impacts, were measured and compared for both molecular and fragment ions. In contrast to targets that are orders of magnitude thicker than the penetration range of the primary ions, secondary ion yields from polyatomic projectile impacts on self-assembled monolayers show little to no enhancement when compared with monatomic projectiles at the same velocity. This unusual trend is most likely due to the structural arrangement and bonding characteristics of the monolayer molecules with the Au(111). Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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Background
Tone languages such as Thai and Mandarin Chinese use differences in fundamental frequency (F0, pitch) to distinguish lexical meaning. Previous behavioral studies have shown that native speakers of a non-tone language have difficulty discriminating among tone contrasts and are sensitive to different F0 dimensions than speakers of a tone language. The aim of the present ERP study was to investigate the effect of language background and training on the non-attentive processing of lexical tones. EEG was recorded from 12 adult native speakers of Mandarin Chinese, 12 native speakers of American English, and 11 Thai speakers while they were watching a movie and were presented with multiple tokens of low-falling, mid-level and high-rising Thai lexical tones. High-rising or low-falling tokens were presented as deviants among mid-level standard tokens, and vice versa. EEG data and data from a behavioral discrimination task were collected before and after a two-day perceptual categorization training task.Results
Behavioral discrimination improved after training in both the Chinese and the English groups. Low-falling tone deviants versus standards elicited a mismatch negativity (MMN) in all language groups. Before, but not after training, the English speakers showed a larger MMN compared to the Chinese, even though English speakers performed worst in the behavioral tasks. The MMN was followed by a late negativity, which became smaller with improved discrimination. The High-rising deviants versus standards elicited a late negativity, which was left-lateralized only in the English and Chinese groups.Conclusion
Results showed that native speakers of English, Chinese and Thai recruited largely similar mechanisms when non-attentively processing Thai lexical tones. However, native Thai speakers differed from the Chinese and English speakers with respect to the processing of late F0 contour differences (high-rising versus mid-level tones). In addition, native speakers of a non-tone language (English) were initially more sensitive to F0 onset differences (low-falling versus mid-level contrast), which was suppressed as a result of training. This result converges with results from previous behavioral studies and supports the view that attentive as well as non-attentive processing of F0 contrasts is affected by language background, but is malleable even in adult learners. 相似文献4.
A formal synthesis of enantiomerically pure (−)-swainsonine was successfully achieved using intramolecular cyclization of the amino alcohol 4 which was derived from a readily available 1-(R)-α-methylbenzylaziridine-2-carboxylic acid (−)-menthol ester 6. 相似文献
5.
Kang MJ Lee S Kim BK Eum JY Park SH Kang MH Oh CH Choo J Choi YW 《Chemical & pharmaceutical bulletin》2011,59(1):109-112
A Pep-1 peptide-modified liposomal (Pep1-Lipo) carrier system was investigated to increase the intracellular delivery of gold nanoparticles (Au NPs). Au NPs with a mean diameter of 13 nm were successfully encapsulated into the inner aqueous compartment of the novel carrier using an ethanol injection technique, reserving the distinctive optical characteristics of the surface plasmon resonance peak around 530 nm. The Au NP-loaded liposomal carrier was physically characterized as 150-170 nm in size and 45 mV in zeta potential. Dark field microscopic observation demonstrated that in vitro cellular association and/or translocation of the nanoprobes into the cells was increased by Pep1-Lipo carriers compared to bare Au NPs. In conclusion, this novel liposomal formulation is a promising platform for the intracellular delivery of metallic nanoprobes including Au NPs. 相似文献
6.
We find some modularity criterion for a product of Klein forms of the congruence subgroup Γ1(N) (Theorem 2.6) and, as its application, construct a basis of the space of modular forms for Γ1(13) of weight 2 (Example 3.4). In the process we face with an interesting property about the coefficients of certain theta function from a quadratic form and prove it conditionally by applying Hecke operators (Proposition 4.3). 相似文献
7.
Chong Shik Chin Hyungeui Lee Myung Ki Lee Soyoung Noh Min-Sik Eum Seunggweon Hong 《Journal of organometallic chemistry》2005,690(5):1306-1313
Alkyl-carbonyl-iridium [Ir(CH3)(CO)(η2-O2CR′)(PPh3)2]+ (1, R′ = CH3, Ph, p-C6H4CH3) react with alkynes (RCCH; R = Ph, p-C6H4CH3) in the presence of NEt3 to give acyl-alkynyl-iridium Ir(C(O)CH3)(-CCR)(η2-O2CR′)(PPh3)2 (4) which further react with RCCH to give alkyl-carbonyl-cis-bis(alkynyl) iridium Ir(CH3)(CO)(CCR)2(PPh3)2 (5). cis-Bis(alkenyl)iridium complexes, Ir(-CHCH2)2(η2-O2CCH3)(PPh3)2 (6) and (η2-O2CCH3)(PPh3)2 (7) react with substituted alkynes RCCH (R = Ph, p-C6H4CH3, cyclohex-1-enyl) to give cis-bis(alkynyl) Ir(CCR)2(η2-O2CCH3)(PPh3)2 (9) that further react with RCCH to undergo the alkyne insertion reaction into the Ir-O bond to produce iridacycles containing vinyl acetate ligands, (-CCR)2(PPh3)2 (8). 相似文献
8.
Eum WS Li MZ Sin GS Choi SY Park JB Lee JY Kwon HY 《Experimental & molecular medicine》2003,35(5):379-384
Dexamethasone converts pluripotent pancreatic AR42J cells into exocrine cells expressing digestive enzymes. In order to address molecular mechanism of this differentiation, we have investigated the role of mitogen-activated protein (MAP) kinase pathway and gene expressions of p21(waf1/cip1) and nuclear oncogenes (c-fos and c-myc) during AR42J cell differentiation. Dexamethasone markedly increased the intracellular and secreted amylase contents as well as its mRNA level. However, cell growth and DNA content were significantly decreased. With these phenotypic changes, AR42J cells induced transient mRNA expression of p21(waf1/cip1) gene, which reached maximal level by 6 h and then declined gradually toward basal state. In contrast to p21(waf1/cip1), c-fos gene expression was transiently inhibited by 6 h and then recovered to basal level by 24 h. Increased c-myc expression detected after 3 h, peaked by 12 h, and remained elevated during the rest of observation. Dexamethasone inhibited epidermal growth factor-induced phosphorylation of extracellular signal regulated kinase. Inhibition of MAP kinase pathway by PD98059 resulted in further elevation of the dexamethasone-induced amylase mRNA and p21(waf1/cip1) gene expression. These results suggest that p21(waf1/cip1) and nuclear oncogenes are involved in dexamethasone-induced differentiation and inhibition of MAP kinase pathway accelerates the conversion of undifferentiated AR42J cells into amylase-secreting exocrine cells. 相似文献
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10.
Ick Sun Eum 《印度理论与应用数学杂志》2018,49(3):521-526
The Catalan-Mersenne numbers cn are double Mersenne numbers defined by c0 = 2 and \({c_n} = {2^{{c_{n - 1}}}} - 1\) for positive integers n. We prove a certain congruence relation of the Catalan- Mersenne numbers. 相似文献