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151.
Jhillu S. Yadav Basi V. Subba Reddy Ashutosh P. Singh Ashok K. Basak 《Tetrahedron letters》2008,49(41):5880-5882
The conversion of alkenes into α-iodoketones has been achieved in good yields and with high regioselectivity by means of iodohydrin formation and subsequent oxidation with 2-iodoxybenzoic acid (IBX) under mild conditions. Aromatic alkynes are also converted into their corresponding α-iodoketones under similar conditions. 相似文献
152.
Y. Suman Reddy P. Kadigachalam Ranjan K. Basak A.P. John Pal Yashwant D. Vankar 《Tetrahedron letters》2012,53(2):132-136
A simple and divergent route for the total synthesis of pericosine B and pericosine C and their enantiomers from d-ribose by using the Baylis–Hillman reaction and ring-closing metathesis reactions as key steps has been described. 相似文献
153.
Thander A Basak D Mallik B 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(10):2393-2398
The changes in the electronic absorption spectra (UV-Vis) (after photoexcitation) of poly(methyl methacrylate) (PMMA) thin films doped with a metallocene and containing chloroform molecules as impurities, have been studied as a function of photoexcitation wavelength (210-750 nm), photoexcitation time (duration), amount of metallocene in the film and amount of chloroform molecules present in the film. Photoeffects on the metallocenes have been observed, which depend significantly on the nature of the central metal atom of the metallocene and the results have been discussed on the basis of the electronic configuration of the metallocenes, which is under study. 相似文献
154.
Supriyo Majumder 《Tetrahedron》2010,66(17):3152-812
A titanium-catalyzed 3-component coupling reaction can be used to generate tautomers of 1,3-diimines. These diimines produced in situ undergo condensation with amidines in a one-pot procedure to provide substituted pyrimidines. Seventeen examples of pyrimidines are provided using this one-pot, 4-component procedure from simple starting materials. In some cases, catalyst architecture can be tuned to control the regioselectivity of the alkyne addition. Finally, the regioselectivity of amidine addition to unsymmetrical 1,3-diimines is discussed. 相似文献
155.
B Kükrer IM Barbu J Copps P Hogan SS Taylor E van Duijn AJ Heck 《Journal of the American Society for Mass Spectrometry》2012,23(9):1534-1543
In the gas-phase, ions of protein complexes typically follow an asymmetric dissociation pathway upon collisional activation, whereby an expelled small monomer takes a disproportionately large amount of the charges from the precursor ion. This phenomenon has been rationalized by assuming that upon activation, a single monomer becomes unfolded, thereby attracting charges to its newly exposed basic residues. Here, we report on the atypical gas-phase dissociation of the therapeutically important, heterodimeric calcium/calmodulin-dependent serine/threonine phosphatase calcineurin, using a combination of tandem mass spectrometry, ion mobility mass spectrometry, and computational modeling. Therefore, a hetero-dimeric calcineurin construct (62?kDa), composed of CNa (44?kDa, a truncation mutant missing the calmodulin binding and auto-inhibitory domains), and CNb (18?kDa), was used. Upon collisional activation, this hetero-dimer follows the commonly observed dissociation behavior, whereby the smaller CNb becomes highly charged and is expelled. Surprisingly, in addition, a second atypical dissociation pathway, whereby the charge partitioning over the two entities is more symmetric is observed. The presence of two gas-phase conformational isomers of calcineurin as revealed by ion mobility mass spectrometry (IM-MS) may explain the co-occurrence of these two dissociation pathways. We reveal the direct relationship between the conformation of the calcineurin precursor ion and its concomitant dissociation pathway and provide insights into the mechanisms underlying this co-occurrence of the typical and atypical fragmentation mechanisms. 相似文献
156.
Basak D Versek C Toscano DT Christensen S Tuominen MT Venkataraman D 《Chemical communications (Cambridge, England)》2012,48(47):5922-5924
In this communication, we introduce squaric acid derivatives as anhydrous proton conductors. We report the synthesis, characterization and proton conductivities of four squaric acid derivatives. The anhydrous proton conductivity of one of the derivatives was 2.3 × 10(-3) S cm(-1) at 110 °C, comparable to the conductivity of molten 1H-1,2,3-triazole or 1H-imidazole. 相似文献
157.
A general synthetic route to beta-lactam-fused enediynes by intramolecular Kinugasa reaction has been successfully developed. The method has widened the scope of Kinugasa reaction in the synthesis of sensitive systems like the one described in this communication. 相似文献
158.
159.
On the dependence of a characterization of proteomics maps on the number of protein spots considered
Randić M Witzmann FA Kodali V Basak SC 《Journal of chemical information and modeling》2006,46(1):116-122
We have reexamined the numerical characterization of proteomics maps based on the construction of novel distance matrices associated with the nearest neighbor graph for the protein spots. In particular we consider dependence of a characterization of proteomics map on the number of proteins considered in the analysis. We examined a collection of proteomics maps in which we approximately doubled the number of spots to be used for quantitative analysis, considering cases of maps having 30, 50, 100, 250, 500, and 1054 protein spots. For each case we have compared the similarity-dissimilarity results for five proteomics maps of rat liver cells associated with the control group and four proliferators administrated by intraperitoneal injection. We found that proteins maps based on a set of about the 250 most abundant proteins spots suffice for a satisfactory numerical characterization of such maps. 相似文献
160.