@article {2549,
	title = {Synthetic Approaches to the Microtubule-Stabilizing Sponge Alkaloid Ceratamine A and Desbromo Analogues},
	journal = {Journal of Organic Chemistry},
	volume = {74},
	number = {3},
	year = {2009},
	note = {ISI Document Delivery No.: 402HHTimes Cited: 6Cited Reference Count: 58Nodwell, Matt Pereira, Alban Riffell, Jenna L. Zimmerman, Carla Patrick, Brian O. Roberge, Michel Andersen, Raymond J.},
	month = {Feb},
	pages = {995-1006},
	type = {Article},
	abstract = {Two synthetic approaches to the microtubule-stabilizing ceratamine alkaloids are described. The first approach involved attempts to graft an aminoimidazole moiety onto an azepine ring to form partially hydrogenated versions of the unprecedented aromatic imidazo[4,5-d]azepine core of the ceratamines. This route ultimately failed because it was not possible to aromatize the partially hydrogenated ceratamine intermediates. A second approach started with tribromoimidazole that was sequentially metalated and functionalized to efficiently generate a key imidazole intermediate containing vinyl bromide and amide functionalities. An intramolecular Buchwald vinyl amidation reaction converted this key intermediate into a bicyclic imidazol[4,5-d]azepine that was at the same oxidation state as the aromatic core of the ceratamines. The 2-amino functionality present on the imidazole ring of the ceratamines was installed using a Buchwald/Hartwig amination reaction on a 2-chloroimidazole precursor. Deprotection and aromatization resulted in the first synthesis of desbromoceratamine A (55) and desmethyldesbromoceratamine A (60). An unanticipated addition of atmospheric oxygen was encountered during deprotection of the imidazole ring in the last step of the synthesis leading to C-11 oxygenated ceratamine analogues as byproducts. Evaluation of the synthetic ceratamines in a TG3 cell-based assay for mitotic arrest revealed that the C-14 and C-16 bromine substituents in ceratamine A (1) play a major role in the antimitotic potency of the natural product. The synthetic route to ceratamine analogues has provided sufficient quantities of desbromoceratamine A (55) for testing in mouse models of cancer.},
	keywords = {6-PI-2-AZATRIENE ELECTROCYCLIZATION, AGELADINE-A, ANTIMITOTIC AGENTS, ARYL CHLORIDES, DIRECTED LITHIATION, HALIDES, IMIDAZOLE, PACLITAXEL, PALLADIUM-CATALYZED AMINATION, TAXOL},
	isbn = {0022-3263},
	url = {<Go to ISI>://000263004300005},
	author = {Nodwell, M. and Pereira, A. and Riffell, J. L. and Zimmerman, C. and Patrick, B. O. and Roberge, M. and Andersen, R. J.}
}
@article {4280,
	title = {Chelate ring-opening ruthenium complexes: X-ray crystal structure and solution studies of cis,trans-bis(2-dimethyl-aminoethyl)diphenylphosphino(dichloro)ruthenium (II)},
	journal = {Inorganica Chimica Acta},
	volume = {273},
	number = {1-2},
	year = {1998},
	note = {ISI Document Delivery No.: ZP204Times Cited: 13Cited Reference Count: 34XXXIII International Conference on Coordination ChemistryAUG 30-SEP 04, 1998FLORENCE, ITALY},
	month = {May},
	pages = {1-7},
	type = {Proceedings Paper},
	abstract = {{The Ru(II) complex cis,trans-[Ru(Me(2)NCH(2)Ch(2)PPh(2)-P,N)(2)Cl-2] (1) has been characterized in the solid state and in solution. X-ray crystallography showed that complex 1 is monoclinic, space group C-2/c; a = 36.0421},
	keywords = {aminophosphine complexes, chelate ring complexes, crystal structures, DERIVATIVES, IMIDAZOLE, METAL-COMPLEXES, PHOSPHINE-LIGANDS, ruthenium complexes, SERIES},
	isbn = {0020-1693},
	url = {<Go to ISI>://000073728200002},
	author = {Guo, Z. J. and Habtemariam, A. and Sadler, P. J. and James, Brian R.}
}
@article {4418,
	title = {Structural, spectroscopic, thermodynamic and kinetic properties of copper(II) complexes with tripodal tetraamines},
	journal = {Inorganic Chemistry},
	volume = {37},
	number = {16},
	year = {1998},
	note = {ISI Document Delivery No.: 110GETimes Cited: 87Cited Reference Count: 38},
	month = {Aug},
	pages = {4022-4029},
	type = {Article},
	abstract = {Spectroscopic, thermodynamic, and kinetic measurements have been made on aqueous solutions of copper(II) complexes of hexamethylated tren and trimethylated tren (one methylation per primary amine group of tren) with the objective of correlating: the influence of geometry (trigonal bipyramidal, evident from UV/vis spectroscopy) and N-alkyl substitution in the ligand on these inherent properties. At 25.0 degrees C the protonation constants of Me(3)tren are not significantly different from those of tren and Me(6)tren, and the stability constant for the Cu(II) complex is of the same order of magnitude as that for the [Cu(tren)(H2O)](2+) complex ion; The pK(a) for deprotonation of the coordinated water molecule of [Cu(Me(3)tren)(H2O)](2+) is intermediate between the values for the complexes containing the unsubstituted and the fully substituted tren ligand. Substitution (pyridine for water) kinetics measurements employing stopped-flow and temperature-jump methods revealed different patterns of reactivity: pyridine replaces water in [Cu(Me(3)tren)(H2O)](2+) with a second-order rate constant of (4.4 +/- 0.8) x 10(2) M-1 s(-1) at 25.0 degrees C, whereas the corresponding process for [Cu(Me(6)tren)(H2O)](2+) is relatively complex and is discussed in more detail. Substitution in the former complex ion is characterized in the forward and reverse directions, by Delta H-double dagger = 60 +/- 8 and 51.9 +/- 0.9 kJ mol(-1), Delta S-double dagger = 5 +/- 27 and -23 +/- 3 J mol(-1) K-1, and Delta V-double dagger = -8.7 +/- 4.6 and -6.2 +/- 1.1 cm(3) mol(-1), respectively, It is concluded that this reaction follows an I-a mechanism, similar to that reported for the comparable reaction of [Cu(tren)(H2O)](2+). An X-ray structural determination on a crystal of [Cu-2(Me(3)tren)(2)(CN)] (ClO4)(3) . 2CH(3)CN demonstrated trigonal bipyramidal geometry about each copper(II) center. As has been found in comparable complexes of tren and Me(6)tren, the axial nitrogen to copper bond is shorter than the equatorial nitrogen-copper bonds, and the angle made by N(axial)-Cu-N(equatorial) is less than 90 degrees (84.6-85.4 degrees), signifying that each copper ion lies below the plane of the equatorial nitrogen atoms.},
	keywords = {AQUEOUS-SOLUTION, CRYSTAL-STRUCTURE, ELECTRONIC-PROPERTIES, IMIDAZOLE, ION, MECHANISM, PHENANTHROLINE, PRESSURE-DEPENDENCE, RESONANCE, SUBSTITUTION KINETICS},
	isbn = {0020-1669},
	url = {<Go to ISI>://000075371200019},
	author = {Thaler, F. and Hubbard, C. D. and Heinemann, F. W. and vanEldik, R. and Schindler, S. and Fabian, I. and Dittler-Klingemann, A. M. and Hahn, F. E. and Orvig, Chris}
}
@article {3799,
	title = {Characterization of a buried neutral histidine residue in Bacillus circulans xylanase: NMR assignments, pH titration, and hydrogen exchange},
	journal = {Protein Science},
	volume = {5},
	number = {11},
	year = {1996},
	note = {ISI Document Delivery No.: VQ786Times Cited: 41Cited Reference Count: 63},
	month = {Nov},
	pages = {2319-2328},
	type = {Article},
	abstract = {Bacillus circulans xylanase contains two histidines, one of which (His 156) is solvent exposed, whereas the other (His 149) is buried within its hydrophobic core. His 149 is involved in a network of hydrogen bonds with an internal water and Ser 130, as well as a potential weak aromatic-aromatic interaction with Tyr 105. These three residues, and their network of interactions with the bound water, are conserved in four homologous xylanases. To probe the structural role played by His 149, NMR spectroscopy was used to characterize the histidines in BCX. Complete assignments of the H-1, C-13, and N-15 resonances and tautomeric forms of the imidazole rings were obtained from two-dimensional heteronuclear correlation experiments. An unusual spectroscopic feature of BCX is a peak near 12 ppm arising from the nitrogen bonded H-1(epsilon 2) of His 149. Due to its solvent inaccessibility and hydrogen bonding to an internal water molecule, the exchange rate of this proton (4.0 X 10(-5) s(-1) at pH* 7.04 and 30 degrees C) is retarded by > 10(6)-fold relative to an exposed histidine. The pK(a) of His 156 is unperturbed at similar to 6.5, as measured from the pH dependence of the N-15- and H-1-NMR spectra of BCX. In contrast, His 149 has a pK(a) < 2.3, existing in the neutral (NH)-H-epsilon 2 tautomeric state under all conditions examined. BCX unfolds at low pH and 30 degrees C, and thus His 149 is never protonated significantly in the context of the native enzyme. The structural importance of this buried histidine is confirmed by the destablizing effect of substituting a phenylalanine or glutamine at position 149 in BCX.},
	keywords = {ACTIVE-SITE, ALPHA-HELICES, AQUEOUS-SOLUTION, CHEMICAL-SHIFTS, ESCHERICHIA-COLI, GLYCOSYL HYDROLASES, H-1-NMR SPECTRUM, HYDROGEN-DEUTERIUM EXCHANGE, IMIDAZOLE, internal water, L-ALA-OH, NUCLEAR MAGNETIC-RESONANCE, pH titration, pK(alpha), PROTEIN HYDRATION, protein stability},
	isbn = {0961-8368},
	url = {<Go to ISI>://A1996VQ78600018},
	author = {Plesniak, L. A. and Connelly, G. P. and Wakarchuk, W. W. and McIntosh, L. P.}
}
