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Biomimetic tris(4-imidazolyl)carbinol derivatives are prepared from imidazole in a short, high-yielding sequence via sulfonamide 1, which is converted to the 2-silylated carbinol 2 by one-pot, sequential 2-functionalization and then 4(5)-functionalization. Alcohol 2 can be transformed either to the parent carbinol 3 or to a desilylated sulfonamide derivative 4. The tripodal alcohol 3 is a convenient precursor to ethers by solvolysis and to metal complexes, as illustrated by the preparation of a bis-tripod complex with iron(III). 相似文献
3.
Andrew G McDonald Sinéad Boyce Gerard P Moss Henry BF Dixon Keith F Tipton 《BMC biochemistry》2007,8(1):14
Background
We describe the database ExplorEnz, which is the primary repository for EC numbers and enzyme data that are being curated on behalf of the IUBMB. The enzyme nomenclature is incorporated into many other resources, including the ExPASy-ENZYME, BRENDA and KEGG bioinformatics databases. 相似文献4.
tert-Butanesulfinyl aldimines and ketimines bearing an alpha-benzyloxy or alpha-silyloxy substituent serve as precursors in the synthesis of protected 1,2-amino alcohols in high yields and diastereoselectivities. General protocols are described for the addition of unbranched alkyl, branched alkyl, and aryl organometallic reagents to N-sulfinyl aldimines 1 and 2 and ketimines 5 and 6. Furthermore, the selective N- or O-deprotection of sulfinamide products 3, 4, 7, and 8 is described, enabling further synthetic transformations of the reaction products. 相似文献
5.
Synthetic routes to tris(imidazolyl)carboxylate ligands and representative metal complexes are reported, which provide more accurate active site models for several classes of redox metalloenzymes. In the first route a hydroxypivalate ester is converted in four regioselective steps to an imidazole diester 4; this is then converted to tris(imidazolyl)carboxylic acid ligand 9, featuring regiospecific double addition of an N-protected lithio-imidazole to an imidazole diester 8. Ligand 9 forms a Co(III) complex, (9)(9-H)Co (10), characterized by X-ray diffraction, coordinated via two imidazole units and the carboxylate. A second route was developed, which provides more soluble ligands that are less prone to form oligomeric complexes. It utilizes addition of the Grignard reagent from 4-iodo-2-isopropylimidazole 12 to an imidazole diester 13, producing atropisomeric tris(imidazolyl)carbinol esters 15M. Treatment of 15M with [Cu(CH3CN)4]PF6 gives a trinuclear complex 16 having alkoxide bridges between neighboring Cu atoms. A third route avoids the bridging alkoxo groups by reduction of tris(imidazolyl)carbinol 15M to the tris(imidazolyl)methane ester 17, which is hydrolyzed to the tris(imidazolyl)methane carboxylic acid 11a. This ligand reacts with [Cu(CH3CN)4]PF6 to produce dinuclear complex [(11a-H)2Cu2](PF6)2 (18), whose X-ray crystal structure shows each copper in a distorted square pyramidal geometry with coordination to the three imidazoles and two bridging carboxylate oxygens. Complex 18 is geometrically similar to the active site copper in quercetin 2,3-dioxygenase. 相似文献
6.
Rutledge SE Volkman HM Schepartz A 《Journal of the American Chemical Society》2003,125(47):14336-14347
Potent and specific inhibitors of protein.protein interactions have potential both as therapeutic compounds and biological tools, yet discovery of such molecules remains a challenge. Our laboratory has recently described a strategy, called protein grafting, for the identification of miniature proteins that bind protein surfaces with high affinity and specificity and inhibit the formation of protein.protein complexes. In protein grafting, those residues that comprise a functional alpha-helical binding epitope are stabilized on the solvent-exposed alpha-helical face of the small yet stable protein avian pancreatic polypeptide (aPP). Here we use protein grafting in combination with molecular evolution by phage display to identify phosphorylated peptide ligands that recognize the shallow surface of CBP KIX with high nanomolar to low micromolar affinity. Furthermore, we show that grafting of the CBP KIX-binding epitope of CREB KID onto the aPP scaffold yields molecules capable of high affinity recognition of CBP KIX even in the absence of phosphorylation. Importantly, both classes of designed ligands exhibit high specificity for the target CBP KIX domain over carbonic anhydrase and calmodulin, two unrelated proteins that bind hydrophobic or alpha-helical molecules that might be encountered in vivo. 相似文献
7.
Unusual long-chain, diunsaturated alkenones and alkyl alkenoates exhibiting double bonds separated by three methylene units instead of the more usual five were characterized by electron ionization (EI) gas chromatography/mass spectrometry. In a first step, the positions of the double bonds of these compounds (isolated from Holocene Black Sea sediments) were confirmed after OsO4 treatment and silylation. Mass spectra of the resulting tetratrimethylsilyloxy derivatives allowed unambiguous determination of the positions of unsaturations. The EI mass spectra of the non-derivatized compounds were then compared with those of the alkenones and alkyl alkenoates having double bonds separated by five methylene units. Specific fragment ions resulting from gamma-H rearrangements were found to be prominent in EI mass spectra of these unusual 'Black Sea' diunsaturated alkenones and alkyl alkenoates. These fragment ions can be used to characterize these compounds in natural samples without the need for laborious derivatization treatments. 相似文献
8.
Sun Q Tyler RC Volkman BF Julian RR 《Journal of the American Society for Mass Spectrometry》2011,22(3):399-407
The human chemokine lymphotactin (Ltn) is a remarkable protein that interconverts between two unrelated native state structures
in the condensed phase. It is possible to shift the equilibrium toward either conformation with selected sequence substitutions.
Previous results have shown that a disulfide-stabilized variant preferentially adopts the canonical chemokine fold (Ltn10),
while a single amino acid change (W55D) favors the novel Ltn40 dimeric structure. Selective noncovalent adduct protein probing
(SNAPP) is a recently developed method for examining solution phase protein structure. Herein, it is demonstrated that SNAPP
can easily recognize and distinguish between the Ltn10 and Ltn40 states of lymphotactin in aqueous solution. The effects of
organic denaturants, acid, and disulfide bond reduction and blocking were also examined using SNAPP for the CC3, W55D, and
wild type proteins. Only disulfide reduction was shown to significantly perturb the protein, and resulted in considerably
decreased adduct formation consistent with loss of tertiary/secondary structure. Cold denaturation experiments demonstrated
that wild-type Ltn is the most temperature sensitive of the three proteins. Examination of the higher charge states in all
experiments, which are presumed to represent transition state structures between Ltn-10 and Ltn-40, reveals increased 18C6
attachment relative to the more folded structures. This observation is consistent with increased competitive intramolecular
hydrogen bonding, which may guide the transition. Experiments examining the gas phase structures revealed that all three proteins
can be structurally distinguished in the gas phase. In addition, the gas phase experiments enabled identification of preferred
adduct binding sites. 相似文献
9.
Jean-Claude Daran Nicolas Gimeno Maryse Gouygou Jrme Volkman 《Acta Crystallographica. Section C, Structural Chemistry》2019,75(5):523-528
The self‐assembly of ditopic bis(1H‐imidazol‐1‐yl)benzene ligands ( L H) and the complex (2,2′‐bipyridyl‐κ2N,N′)bis(nitrato‐κO)palladium(II) affords the supramolecular coordination complex tris[μ‐bis(1H‐imidazol‐1‐yl)benzene‐κ2N3:N3′]‐triangulo‐tris[(2,2′‐bipyridyl‐κ2N,N′)palladium(II)] hexakis(hexafluoridophosphate) acetonitrile heptasolvate, [Pd3(C10H8N2)3(C12H10N4)3](PF6)6·7CH3CN, 2 . The structure of 2 was characterized in acetonitrile‐d3 by 1H/13C NMR spectroscopy and a DOSY experiment. The trimeric nature of supramolecular coordination complex 2 in solution was ascertained by cold spray ionization mass spectrometry (CSI–MS) and confirmed in the solid state by X‐ray structure analysis. The asymmetric unit of 2 comprises the trimetallic Pd complex, six PF6? counter‐ions and seven acetonitrile solvent molecules. Moreover, there is one cavity within the unit cell which could contain diethyl ether solvent molecules, as suggested by the crystallization process. The packing is stabilized by weak inter‐ and intramolecular C—H…N and C—H…F interactions. Interestingly, the crystal structure displays two distinct conformations for the L H ligand (i.e. syn and anti), with an all‐syn‐[Pd] coordination mode. This result is in contrast to the solution behaviour, where multiple structures with syn/anti‐ L H and syn/anti‐[Pd] are a priori possible and expected to be in rapid equilibrium. 相似文献
10.
M Julia BF Flaminio Alexandre S Borges Daryl V Nydam David W Horohov Rolf Hecker Mary Beth Matychak 《Journal of immune based therapies and vaccines》2007,5(1):1-17