1H-Pyrazolo[3,4-b]quinolines: Synthesis and Properties over 100 Years of Research

This paper summarises a little over 100 years of research on the synthesis and the photophysical and biological properties of 1H-pyrazolo[3,4-b]quinolines that was published in the years 1911–2021. The main methods of synthesis are described, which include Friedländer condensation, synthesis from anthranilic acid derivatives, multicomponent synthesis and others. The use of this class of compounds as potential fluorescent sensors and biologically active compounds is shown. This review intends to summarize the abovementioned aspects of 1H-pyrazolo[3,4-b]quinoline chemistry. Some of the results that are presented in this publication come from the laboratories of the authors of this review.     

The visualisation of the targeting of phospholipid liposomes to bacteria

Anionic and cationic phospholipid liposomes have been prepared from dipalmitoylphosphatidylcholine (DPPC) — phosphatidylinositol (PI) and DPPC-cholesterol-stearylamine (SA) mixtures over a range of composition and targeted to biofilms of the skin-associated bacterium Staphylococcus epidermidis to establish the optimum PI and SA content for targeting. The interaction of liposomes of optimum composition with the bacteria were visualized by electron microscopy using negative staining with uranyl acetate and phosphotungstic acid. It has been demonstrated that the liposomes absorb extensively to the bacterial surface. Immunoliposomes have been prepared with a covalently linked monoclonal antibody raised to antigenic determinants on the surface of the oral bacterium Streptococcus oralis. The targeting of the immunoliposomes to this bacterium has been visualized using a second gold labelled anti-antibody. As for the anionic and cationic liposomes the immunoliposomes adsorb to the surface of the bacteria. The results add support to the concept of using liposomes for the delivery of bactericides or therapeutic agents to bacteria.     

A study on application of impregnated synthetic peptide TLC stationary phases for the screening of 5-HT1A ligands. Part 2

Six extended analogues of the recently described peptides (LDVL, ADVL) were designed and synthesized on a solid support, and then impregnated on TLC stationary phases. The impact of the impregnated peptide sequence modifications on the chromatographic retard, Delta R(f) (difference in the migration of tested compound on control and impregnated plates), of 42 arylpiperazine 5-HT(1A) receptor ligands was studied. None of the new models tested made a better prediction of 5-HT(1A) affinity than that utilizing ADVL tetrapeptide. Further validation of the ADVL model on a set of 22 structurally differentiated 2-methoxy-phenylpiperazine derivatives confirmed its effectiveness in the affinity discrimination of a coherent group of 5-HT(1A) receptor ligands.     

Thermal stability study of the protease inhibitors

A thermal and kinetic analysis of two protease inhibitors: nelfinavir mesylate and atazanavir sulfate, were carried out to find their thermal stability. DSC curves of both drugs showed exothermic transition. This observed process resulted in two steps. Obtained apparent activation energy pointed at low stability of studied protease inhibitors in water solutions.     

Unexpected role of O-2 "protecting" groups of glycosyl donors in mediating regioselective glycosidation

Glycosidation of several vicinal diols reveals that exquisite regioselectivity can be achieved by using 2-O-benzoyl n-pentenyl glycoside donors and/or their cyclic 1,2-ortho ester counterparts. The regioselective preferences for both are the same, although ratios and yields may differ. In stark contrast, glycosidation of the diols with the corresponding 2-O-benzylated donors gives poor, if any, regioselectivity.     

Surface‐Guided Formation of an Organocobalt Complex

Organocobalt complexes represent a versatile tool in organic synthesis as they are important intermediates in Pauson–Khand, Friedel–Crafts, and Nicholas reactions. Herein, a single‐molecule‐level investigation addressing the formation of an organocobalt complex at a solid–vacuum interface is reported. Deposition of 4,4′‐(ethyne‐1,2‐diyl)dibenzonitrile and Co atoms on the Ag(111) surface followed by annealing resulted in genuine complexes in which single Co atoms laterally coordinated to two carbonitrile groups undergo organometallic bonding with the internal alkyne moiety of adjacent molecules. Alternative complexation scenarios involving fragmentation of the precursor were ruled out by complementary X‐ray photoelectron spectroscopy. According to density functional theory analysis, the complexation with the alkyne moiety follows the Dewar–Chatt–Duncanson model for a two‐electron‐donor ligand where an alkyne‐to‐Co donation occurs together with a strong metal‐to‐alkyne back‐donation.     

p-Phenyleneethynylene molecular wires: influence of structure on photoinduced electron-transfer properties

A series of donor-acceptor arrays (exTTF-oPPE-C60) containing pi-conjugated oligo(phenyleneethynylene) wires (oPPE) of different length between pi-extended tetrathiafulvalene (exTTF) as electron donor and fullerene (C60) as electron acceptor has been prepared by following a convergent synthesis. The key reaction in these approaches is the bromo-iodo selectivity of the Hagihara-Sonogashira reaction and the deprotecting of acetylenes with different silyl groups to afford the corresponding donor-acceptor conjugates in moderate yields. The electronic interactions between the three electroactive species were determined by using UV-visible spectroscopy and cyclic voltammetry. Our studies clearly confirm that, although the C60 units are connected to the exTTF donor through pi-conjugated oPPE frameworks, no significant electronic interactions are observed in the ground state. Theoretical calculations predict how a simple exchange from C=C double bonds (i.e., oligo(p-phenylenevinylene) to C triple chemical bond C triple bonds (i.e., oPPE) in the electron donor-acceptor conjugates considerably alters long-range electron transfer. Photoexcitation of exTTF-oPPE-C60 leads to the following features: a transient photoproduct with maxima at 660 and 1000 nm, which are unambiguously attributed to the photolytically generated radical-ion-pair state, [exTTF*+-oPPE-C60*]. Both charge-separation and charge-recombination processes give rise to a molecular-wire behaviour of the oPPE moiety with an attenuation factor (beta) of (0.2+/-0.05) A(-1).     

Influence of diamino acid derivatives of protoporphyrin IX on mouse immunological system: preliminary results

Immunological response related to photodynamic therapy (PDT) is one of the basic elements that influence on the efficiency of this cancer treatment method. Diamino acid derivatives of protoporphyrin IX are promising photosensitizing agents that are intended to be the components of new anti-tumor drug. The influence of three derivatives - PP(Ser)(2)Arg(2), PP(Ala)(2)Arg(2), PP(Phe)(2)Arg(2) and a mixture of these compounds called Sensyphyrine on mouse immunological system was investigated where animals were exposed and unexposed to the laser irradiation. Porphyrins solutions were injected intravenously, mice were irradiated with the red diode laser at lambda=632 nm. Cells and blood samples were taken at time intervals after irradiation. The levels of interleukin-6, interleukin-1beta and the production of reactive forms of nitrogen by macrophages were determined. The results show that all of the diamino acid derivatives of protoporphyrin IX indicate an immunological response when the light is applied. Each of the porphyrin revealed different impact on mice immunological system. The most potent stimulant properties disclosed PP(Phe)(2)Arg(2) derivative for which the highest values of IL-1beta, IL-6 and NO(2)(-) were noticed. The weakest immunological activation revealed PP(Ser)(2)Arg(2) derivative.     

Learning from the acquired optimized pulse shapes about the isotope selective ionization of potassium dimers

Selective optimization of the 39,39K2 and 39,41K2 isotopomers in a three-photon ionization process is presented by applying evolution strategies on shaped fs pulses in a feedback loop. The optimizations at different center wavelengths show considerably large enhancements of one isotope compared to the other and reversed. We compare the acquired optimized pulse shapes for combined phase and amplitude with pure amplitude modulation. Particularly from their spectra we are able to extract information about the optimally chosen differing ionization paths via the involved vibrational states. Furthermore, a comparison of the temporal shape of the optimized pulse forms for combined phase and amplitude with pure phase optimization is given. The presented pulse form analysis demonstrates the potential of restricted optimization to gain insight into the underlying dynamical processes. Our approach reveals how the optimization algorithm precisely addresses the vibrational wave functions both spectrally and temporally.