Synthesis and Investigation of Phthalazinones as Antitubercular Agents

A series of 2‐ and 7‐substituted phthalazinones was synthesised and their potential as anti‐tubercular drugs assessed via Mycobacterium tuberculosis (mc²6230) growth inhibition assays. All phthalazinones tested showed growth inhibitory activity (MIC <100 μm ), and those compounds containing lipophilic and electron‐withdrawing groups generally exhibited better anti‐tubercular activity. Several lead compounds were identified, including 7‐((2‐amino‐6‐(4‐fluorophenyl)pyrimidin‐4‐yl)amino)‐2‐heptylphthalazin‐1(2H)‐one (MIC=1.6 μm ), 4‐tertbutylphthalazin‐2(1H)‐one (MIC=3 μm ), and 7‐nitro‐phthalazin‐1(2H)‐one (MIC=3 μm ). Mode of action studies indicated that selected pyrimidinyl‐phthalazinones may interfere with NADH oxidation, however, the mode of action of the lead compound is independent of this enzyme. MIC=minimum inhibitory concentration.     

Analysis of Single‐Molecule Fluorescence Spectroscopic Data with a Markov‐Modulated Poisson Process

We present a photon‐by‐photon analysis framework for the evaluation of data from single‐molecule fluorescence spectroscopy (SMFS) experiments using a Markov‐modulated Poisson process (MMPP). A MMPP combines a discrete (and hidden) Markov process with an additional Poisson process reflecting the observation of individual photons. The algorithmic framework is used to automatically analyze the dynamics of the complex formation and dissociation of Cu²⁺ ions with the bidentate ligand 2,2′‐bipyridine‐4,4′dicarboxylic acid in aqueous media. The process of association and dissociation of Cu²⁺ ions is monitored with SMFS. The dcbpy‐DNA conjugate can exist in two or more distinct states which influence the photon emission rates. The advantage of a photon‐by‐photon analysis is that no information is lost in preprocessing steps. Different model complexities are investigated in order to best describe the recorded data and to determine transition rates on a photon‐by‐photon basis. The main strength of the method is that it allows to detect intermittent phenomena which are masked by binning and that are difficult to find using correlation techniques when they are short‐lived.     

A sequential cyclization/π-extension strategy for modular construction of nanographenes enabled by stannole cycloadditions

The synthesis of polycyclic aromatic hydrocarbons (PAHs) and related nanographenes requires the selective and efficient fusion of multiple aromatic rings. For this purpose, the Diels–Alder cycloaddition has proven especially useful; however, this approach currently faces significant limitations, including the lack of versatile strategies to access annulated dienes, the instability of the most commonly used dienes, and difficulties with aromatization of the [4 + 2] adduct. In this report we address these limitations via the marriage of two powerful cycloaddition strategies. First, a formal Cp₂Zr-mediated [2 + 2 + 1] cycloaddition is used to generate a stannole-annulated PAH. Secondly, the stannoles are employed as diene components in a [4 + 2] cycloaddition/aromatization cascade with an aryne, enabling π-extension to afford a larger PAH. This discovery of stannoles as highly reactive – yet stable for handling – diene equivalents, and the development of a modular strategy for their synthesis, should significantly extend the structural scope of PAHs accessible by a [4 + 2] cycloaddition approach.

Stannoles are introduced as a new, spontaneously aromatizing diene for [4 + 2] cycloadditions that can be easily introduced into diverse conjugated systems, facilitating the efficient synthesis of complex PAHs and their π-extension.     

Über Chalkogenolate. 191. Ester der 2-Oxophenyldithioessigsäure 2. Kristall- und Molekülstruktur des Methylesters

On Chalcogenolates. 191. Esters of 2-Oxophenyldithioacetic Acid. 2. Crystal and Molecular Structure of the Methyl Ester The title compound C₆H₅? CO? CS? SCH₃ crystallizes with Z = 2 in the triclinic space group P1 with cell dimensions (?60°C) a = 6.236(4) Å, b = 7.972(2) Å, c = 9.589(4) Å, α = 88.42(3)°, β = 75.39(5)°, γ = 81.54(4)°. The structure has been determined from single crystal X-ray data measured at ?60°C and refined to R = 0.085 and R_w = 0.087 for 2307 independent reflections. With nearly 20° the C?O bond is turned out of the plane of the phenyl ring.     

Synthesis, structure and emission properties of spirocyclic benzofuranones and dihydroindolones: a domino insertion-coupling-isomerization- Diels-Alder approach to rigid fluorophores

An alkynoyl ortho-iodo phenolester or alkynoyl ortho-iodo anilides and propargyl allyl ethers react under Sonogashira coupling conditions in the sense of an insertion-coupling-isomerization-Diels-Alder hetero domino reaction to furnish (tetrahydroisobenzofuran)-spirobenzofuranones and -spirodihydroindolones in good yields. Many representatives can be crystallized and single crystal structure analyses display steric and electronic substituent effects on the torsional angles of the terminal (hetero)aryl groups and the central cis,trans-butadiene fragment. DFT computations reveal that in the final pericyclic step the Diels-Alder termination is by far thermodynamically and kinetically favored over a possible Claisen rearrangement. Compounds of this new class of spirocyclic compounds possess large Stokes shifts and fluoresce intensively with blue over green to orange colors. As a consequence of the spirocyclic rigidity fluorescence lifetimes and quantum yields are rather high in some cases.     

SYNTHESIS AND CHARACTERIZATION OF HYDROPHOBIC-HYDROPHILIC MULTIBLOCK COPOLYMERS FOR BIOMEDICAL APPLICATIONS*

The synthesis and characterization of amphiphilic copolymers of poly(dimethyl siloxane)(PDMS),poly(ethylene oxide)(PEO), and heparin(Hep) were investigated. These multiblock copolymers wereidentified using ~1H-NMR, FTIR, end group analysis, and sulfur elemental analysis. The multiblockcopolymers were characterized by using DSC and X-ray diffractometry. The glass transition temperature,crystalline melting characteristics, annealing effect, and cold crystallization of the block copolymers weredetermined by DSC. The crystallinity of the block copolymers was also determined by X-ray diffractionmethod.