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71.
Fructos MR Belderrain TR Nicasio MC Nolan SP Kaur H Díaz-Requejo MM Pérez PJ 《Journal of the American Chemical Society》2004,126(35):10846-10847
The complex IPrCuCl (1) catalyzes the transfer of the :CHCO2Et group from ethyl diazoacetate (EDA) to unsaturated and saturated substrates (olefins, amine, alcohols) with very high yields. In the absence of substrate, the complex 1 does not react with EDA to give the diazo coupling products (fumarate and maleate), a rare example in the field of metal-catalyzed diazocompounds decomposition. 相似文献
72.
73.
A metastable state, characterized by a low degree of mass localization, is identified using density-functional theory (DFT). This free energy minimum, located through the proper evaluation of competing terms in the free energy functional, is independent of the specific form of the DFT used. Computer simulation results on particle motion indicate that this heterogeneous state corresponds to the deeply supercooled state. 相似文献
74.
Dibromoacetyl benzene derivatives on condensation with thiourea give 2-amino-4-arylthiazoles instead of the expected 2-amino-4-aryl-5-bromothiazoles. Attempts have been made to find the reaction pathway. 相似文献
75.
Rajnish Moudgil Damanjit Kaur Rachita Vashisht Prasad V Bharatam 《Journal of Chemical Sciences》2000,112(6):623-629
Ab initio HF/6-31+G*, MP2/6-31+G*, B3LYP/6-31+G* level calculations have been performed on HSe-NH2 to estimate the Se-N rotational barriers and N-inversion barriers. Two conformers have been found withsyn andanti arrangement of the NH2 hydrogens with respect to Se-H bond. The N inversion barriers in selenamide are 1.65, 2.47, 1.93 kcal/mol and the Se-N rotational
barriers are 6.58, 6.56 and 6.12 kcal/mol respectively at HF/6-31+G*, MP2/6-31+G* and B3LYP/6-31+G* levels respectively. The
nN →Σ *Se-H negative hyperconjugation is found to be responsible for the higher rotational barriers. 相似文献
76.
77.
S. B. Beri K. B. Bhalla R. Bhanja A. Bharti V. S. Bhatia G. Claesson S. Garpman S. K. Gupta V. K. Gupta N. Y. Herrstrom B. Jakobsson R. Joseph G. L. Kaul G. Kaur M. Kaur S. Kitroo V. Kumar S. Lokanathan I. Lund L. K. Mangotra I. S. Mitra S. Mookerjee B. Norén A. Oskarsson I. Otterlund Y. Prakash S. Persson N. K. Rao S. Sankhyadhar S. Satti M. M. Sherif K. Söderström S. K. Tuli 《Zeitschrift für Physik A Hadrons and Nuclei》1987,327(4):431-441
40Ar-emulsion interactions are studied, to investigate the question of anomalons, in twoG- 5 emulsion stacks. In about 4600 primary interactions, projectile fragments of Z≧2 for all generations have been followed until they interact or leave the stack. After careful estimation of charges of these fragments, variation of their mean free paths is studied as a function of distance from the preceding interaction. Generation effect,N h dependence and production angle effect are investigated. In addition multi-chain events are analysed separately. Our results do not show anomalons at the 6% level and are consistent with non-occurrence of anomalons. However, this experiment is not sensitive enough to rule out anomalons (with a mfp of the order of 2 to 3 cm) produced at about 1% (or less) level. 相似文献
78.
A novel, efficient and protecting group free enantioselective synthetic approach of (?)-(R)-1 and (+)-(S)-rolipram 2 is described employing the organocatalyzed asymmetric Michael addition, Henry condensation, Wittig olefination and reductive lactamization reactions as key steps. 相似文献
79.
The preparation of some novel 3-(arylideneamino)-3a,8a-dihydroxy-1,3,3a,8a-tetrahydroindeno[1,2-d]imidazole-2,8-diones 8(i–xiv) and 3-(arylideneamino)-3a,8a-dihydroxy-2-thioxo-1,3,3a,8a-tetrahydroindeno[1,2-d]imidazol-8(2H)-ones 9(i–xiv) have been reported through one-pot catalyst-free reaction of aldehydes, semicarbazide hydrochloride/thiosemicarbazide with ninhydrin. All the synthesized compounds have been screened for antimicrobial activity and some of them were observed to possess broad spectrum antibacterial potential as well as significant antagonistic potential against fungal pathogens. 相似文献
80.
Domadia PN Bhunia A Ramamoorthy A Bhattacharjya S 《Journal of the American Chemical Society》2010,132(51):18417-18428
Lipopolysaccharide (LPS) provides a well-organized permeability barrier at the outer membrane of Gram-negative bacteria. Host defense cationic antimicrobial peptides (AMPs) need to disrupt the outer membrane before gaining access to the inner cytoplasmic membrane or intracellular targets. Several AMPs are largely inactive against Gram-negative pathogens due to the restricted permeation through the LPS layer of the outer membrane. MSI-594 (GIGKFLKKAKKGIGAVLKVLTTG) is a highly active AMP with a broad-spectrum of activities against bacteria, fungi, and virus. In the context of LPS, MSI-594 assumes a hairpin helical structure dictated by packing interactions between two helical segments. Residue Phe5 of MSI-594 has been found to be engaged in important interhelical interactions. In order to understand plausible structural and functional inter-relationship of the helical hairpin structure of MSI-594 with outer membrane permeabilization, a mutant peptide, termed MSI-594F5A, containing a replacement of Phe5 with Ala has been prepared. We have compared antibacterial activities, outer and inner membrane permeabilizations, LPS binding affinity, perturbation of LPS micelles structures by MSI-594 and MSI-594F5A peptides. Our results demonstrated that the MSI-594F5A has lower activities against Gram-negative bacteria, due to limited permeabilization through the LPS layer, however, retains Gram-positive activity, akin to MSI-594. The atomic-resolution structure of MSI-594F5A has been determined in LPS micelles by NMR spectroscopy showing an amphipathic curved helix without any packing interactions. The 3D structures, interactions, and activities of MSI-594 and its mutant MSI-594F5A in LPS provide important mechanistic insights toward the requirements of LPS specific conformations and outer membrane permeabilization by broad-spectrum antimicrobial peptides. 相似文献