A trinuclear palladium(II) complex containing N,S‐coordinating 2‐(benzylsulfanyl)anilinide and 1,3‐benzothiazole‐2‐thiolate ligands with a central square‐planar PdN4 motif

The reaction of dichlorido(cod)palladium(II) (cod = 1,5‐cyclooctadiene) with 2‐(benzylsulfanyl)aniline followed by heating in N,N‐dimethylformamide (DMF) produces the linear trinuclear Pd₃ complex bis(μ₂‐1,3‐benzothiazole‐2‐thiolato)bis[μ₂‐2‐(benzylsulfanyl)anilinido]dichloridotripalladium(II) N,N‐dimethylformamide disolvate, [Pd₃(C₇H₄NS₂)₂(C₁₃H₁₂NS)₂Cl₂]·2C₃H₇NO. The molecule has symmetry and a Pd...Pd separation of 3.2012 (4) Å. The outer Pd^II atoms have a square‐planar geometry formed by an N,S‐chelating 2‐(benzylsulfanyl)anilinide ligand, a chloride ligand and the thiolate S atom of a bridging 1,3‐benzothiazole‐2‐thiolate ligand, while the central Pd^II core shows an all N‐coordinated square‐planar geometry. The geometry is perfectly planar within the PdN₄ core and the N—Pd—N bond angles differ significantly [84.72 (15)° for the N atoms of ligands coordinated to the same outer Pd atom and 95.28 (15)° for the N atoms of ligands coordinated to different outer Pd atoms]. This trinuclear Pd₃ complex is the first example of one in which 1,3‐benzothiazole‐2‐thiolate ligands are only N‐coordinated to one Pd centre. The 1,3‐benzothiazole‐2‐thiolate ligands were formed in situ from 2‐(benzylsulfanyl)aniline.     

One‐electron redox properties of DNA nucleobases and common tautomers

The redox properties of DNA play an influential role in several important processes such as DNA mutation and the interaction of DNA with drugs. Structural changes in DNA nucleobases from its canonical form to its tautomeric forms can alter these properties and may lead to DNA mutation due to altered base‐pairing properties. Experimental results for the standard value of DNA redox properties vary due to choice of methodology and solvent. Theoretical determination of these properties is helpful in pinpointing standard values but still vary depending on methodology and chosen experimental benchmark. However, it is of importance to identify the overall trend of electron mobility within DNA while providing reliable standard values for redox reactions. In this work, we present the results of theoretical calculations for redox properties. Using the thermodynamic cycle, we can approximate reliable values. We report the electron affinities, ionization potentials, and redox potential for the canonical DNA nucleobases and their rare tautomers. For each of these properties, we evaluate its overall trend to gain a greater understanding of the role that electron attachment and electron mobility have within the DNA strand. All calculations are computed at the M06‐2X/6–31++G(d,p) level of theory. © 2014 Wiley Periodicals, Inc.     

Syntheses of 5′-amino-2′,5′-dideoxy-2′,2′-difluorocytidine derivatives as novel anticancer nucleoside analogs

A novel class of 5′-amino-2′,5′-dideoxy-2′,2′-difluorocytidine derivatives has been synthesized in order to identify anticancer nucleoside analogs. Several synthetic routes were devised and implemented which relied upon either S_N2 displacement or reductive amination to provide the desired derivatives.     

Calcium-catalyzed Friedel–Crafts addition of 1-methylindole to activated cyclopropanes

The synthesis of γ-indolyl malonates was achieved through the addition of indoles to activated cyclopropanes. These Friedel–Crafts reactions were catalyzed by calcium bis(trifluoromethanesulfonimide), Ca(NTf₂)₂. The addition proceeded with complete regioselectivity and in good to excellent yields. Optimization of the reaction conditions and investigation into the scope of the reaction with regard to substitution on cyclopropane are reported.     

Rheology of cellulose/KSCN/ethylenediamine solutions and coagulation into filaments and films

Dissolution of cellulose in ethylenediamine/potassium thiocyanate (KSCN) was studied as a function of cellulose and KSCN concentration. Concentrations of up to 9% (w/w) cellulose were obtained. Large variations in solution rheology with salt and cellulose concentration were observed, and phases including flowing solutions and gels were identified visually. Rheological data indicated that viscosity decreased with increasing salt or cellulose concentration in certain composition ranges. Viscosity decrease with concentration increase is associated with either onset of liquid crystalline ordering or phase separation in the system. Both of these are quite likely in the cellulose/ethylenediamine/KSCN system, depending on composition. Additionally, comparison of loss (G′′) and storage (G′) moduli confirmed that compositions that exhibited gel behavior at zero shear became liquid at shear rates as low as 1 Hz. Solutions were coagulated into filaments and films using ethanol (CH₃CH₂OH) and methanol (CH₃OH). Infrared spectroscopy (FTIR) indicated that significant quantities of KSCN salt remained in the fibers and films after coagulation. Subsequent washing removed residual KSCN and improved physical properties. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2013–2022, 2005     

Objective Detection of Oral Carcinoma with Multispectral Fluorescence Lifetime Imaging In Vivo

Successful early detection and demarcation of oral carcinoma can greatly impact the associated morbidity and mortality rates. Current methods for detection of oral cancer include comprehensive visual examination of the oral cavity, typically followed by tissue biopsy. A noninvasive means to guide the clinician in making a more objective and informed decision toward tissue biopsy can potentially improve the diagnostic yield of this process. To this end, we investigate the potential of fluorescence lifetime imaging (FLIM) for objective detection of oral carcinoma in the hamster cheek pouch model of oral carcinogenesis in vivo. We report that systematically selected FLIM features can differentiate between low‐risk (normal, benign and low‐grade dysplasia) and high‐risk (high‐grade dysplasia and cancer) oral lesions with sensitivity and specificity of 87.26% and 93.96%, respectively. We also show the ability of FLIM to generate “disease” maps of the tissue which can be used to evaluate relative risk of neoplasia. The results demonstrate the potential of multispectral FLIM with objective image analysis as a noninvasive tool to guide comprehensive oral examination.     

Vibrational-torsional excitation and direct overtone photodissociation of ethyl hydroperoxide at 5nuOH

We have observed OH radical products from the unimolecular dissociation of ethyl hydroperoxide (CH3-CH2OOH) excited to 5nuOH and have collected an action spectrum from 15,600 to 16,800 cm(-1) and an OH product state distribution at the maximum (16,119 cm(-1)). We use a vibrational-torsional model to simulate spectra in the 5nuOH region for the trans and gauche conformers. A combination of the two simulated spectra resembles the experimental action spectrum, provided that the trans conformer is assumed to dominate at room temperature. Energy disposal in the OH fragment yields an upper limit for the O-O bond dissociation energy at D0 < 44 kcal mol(-1).     

Preparation of combinatorial arrays of polymer thin films for transmission electron microscopy analysis

We present a new method for harvesting multiple thin film specimens from polymer combinatorial libraries for transmission electron microscopy (TEM) analysis. Such methods are of interest to researchers who wish to integrate TEM measurements into a combinatorial or high-throughput experimental workflow. Our technique employs poly(acrylic acid) plugs, sequestered in an elastomer gasket, to extract a series of film patches from gradient combinatorial libraries. A strategy for simultaneous deposition of the array of film specimens onto TEM grids also is described. We demonstrate our technique using nanostructured polymer thin film libraries as test cases in which the nanoscale details can be successfully imaged. Microscopy of test case specimens demonstrates that these samples are of sufficient quality for morphology screening via TEM, and in some cases are sufficient for more detailed morphological studies.     

Naturally occurring esterification reactions with bryostatin

Bryostatin structures share a commonality of a central bryophan ring, but each differs due to two groups (R(1) and R(2)) that are attached to the bryophan ring via ester bonds. This research examines the impact that conditions such as UV light, acidic and basic conditions can have on the bryostatin structure in the presence of octanoic acid and water. Mass spectrometry (MS) measurements suggest that bryostatin can easily rearrange into various structures under natural conditions by reacting with carboxylates that are ubiquitous in nature. A second set of measurements suggest bryostatin can be hydrolyzed by water, a reaction that has significant implications in both medicinal applications and extraction procedures.     

p-Iodinations in hydrocarbon media: continuous flow reactor application

Regiospecific iodination of aryl amines, that is, aryl compounds possessing strong electron donating groups (EDG’s) in the p-position, is described. This procedure features not only the unique use of hydrocarbon media for such substitutions but also the absence of any oxidants aside from iodine itself. Further potential of this hydrocarbon media based electrophilic aromatic substitution is demonstrated by the coupling of the iodination with an in situ halogen/lithium exchange and product forming nucleophilic addition in a batch process. The protocol was ultimately scaled to a continuous flow reactor using an isolated p-iodoarylamine. Constituted as described, these procedures possess enhanced atom-economical, green and safety aspects compared to existing literature protocols.