Search Results (7)

The preparation of two 1-acyl-8-pyrrolylnaphthalenes (5 and 6) and one pyrrolone (8) are reported along with the issues complicating the preparations of other compounds. The photophysical behavior of the fused, planar derivative 6 is explored in detail. The fluorescence of 6 shows solvato-chromism due to intramolecular charge transfer in the excited state and enhanced emission in protic solvents. The emission intensity increases very linearly with the H-bond-donating strength of the solvent. Preferential solvation studies, multilinear regression analysis and computational modeling suggest that the fluorescence enhancement results from inhibition of the spin–orbit coupling-promoted intersystem crossing from the π→π* singlet state to an n→π* triplet state. Some of the inhibitions are due to the dielectric stabilization of the excited singlet state. A stronger effect is obtained from H-bonding, which not only further stabilizes the singlet state but also negatively impacts the vibronic coupling between the states. Full article

Phycocyanobilin was computationally investigated by means of DFT calculations in combination with implicit solvation starting from X-ray data. Different conformations and degrees of protonation were considered, and the acidity constants were estimated. The computed data suggest a syn-syn-syn conformation for the molecule, with the two carboxylic groups deprotonated under physiological conditions and weak acidic behavior of one of the pyrrolone heterocycles. The absorption transitions in the visible range were studied by means of TD-DFT calculations, focusing on the molecular orbitals involved. The frontier orbitals have a dominant role in the lowest energy absorption. Full article

Chagas disease is caused by a protozoan parasite called Trypanosoma cruzi. The infection produces a first clinical phase, commonly asymptomatic or showing non-specific symptoms, and a second chronic phase characterized by cardiac and digestive dysfunctions in some individuals with the disease. This disease affects 7 million people and has been categorized by the World Health Organisation as a neglected tropical disease. In addition, the drugs used to combat it were developed in the 1970s and present major toxicity problems and limited efficacy in the chronicity of the disease. This has led to research into new active compounds that are effective against the disease, with studies on cyanoderivatives showing promising activity. In this work, eight active E-cyanoacrylamides/5-imino pyrrolones were studied. Compounds B and F showed excellent activity, while compounds C and G stood out for their lower cytotoxicity. After correlating the activity and cytotoxicity of the compounds, it was observed that compounds B, C, and G obtained the most favourable results. Various cell death studies were carried out with these compounds, and it was determined that all of them produced programmed cell death, with compound B standing out as being at a late stage in the process. Full article

Five new sulfated arylpyrrole and arylpyrrolone alkaloids, denigrins H–L (1–5), along with two known compounds, dictyodendrin B and denigrin G, were isolated from an extract of a New Zealand Dictyodendrilla c.f. dendyi marine sponge. Denigrins H–L represent the first examples of sulfated denigrins, with denigrins H and I (1–2), as derivatives of denigrin D, containing a pyrrolone core, and denigrins J–L (3–5), as derivatives of denigrin E (6), containing a pyrrole core. Their structures were elucidated by interpretation of 1D and 2D NMR spectroscopic data, ESI, and HR-ESI-MS spectrometric data, as well as comparison with literature data. Compounds 1–5, along with six known compounds previously isolated from the same extract, showed minimal cytotoxicity against the HeLa cervical cancer cell line. Full article

Diaryl-furanones are specific analytical reagents for the biochemical detection of primary amines by fluorescence techniques. Well-known reagents are fluorescamine (Fluram) and 2-methoxy-2,4-diphenyl-3(2H)-furanone (MDPF), yielding fluorescent products with λem at 480–490 nm. Although the reaction products claim to be pyrrolinones, recent studies show that they are really 3-oxopyrrole (pyrrolone) derivatives. Both reagents have been used for the cytochemical demonstration of primary amines. In this work, we have applied the fluorescent products of MDPF with amines (n-butylamine, BA; glucosamine, GA; and spermine, Sp), which showed interesting fluorescence reactions with chromatin DNA. 2,4-diphenyl-3-oxopyrrole products (diPOPy) can be easily synthesized according to well-known procedures, by mixing solutions of MDPF in acetone with water at pH 9 containing the amino compounds. DiPOPy derivatives of BA, GA, and Sp were used for spectroscopic, microscopic, and molecular modeling studies, showing a bright and selective blue–green fluorescence on DNA substrates, mainly chromatin, kinetoplast DNA, and stretched chromatin fibers. The cationic diPOPy fluorophore is planar, with a high partial positive charge in the N atom, and suitable for intercalative binding to DNA. A mechanism of fluorescamine fluorescence due to an inner-salt isomeric form is proposed, and an astonishing correlation between adenine–thymine-rich centromeric heterochromatin in mouse metaphase chromosomes after reaction of the fluorescamine reagent with protein amino groups is also discussed. Full article

Three isomeric (benzyloxythienyl)oxazolines 9, 11 and 13 have been prepared and are found, upon treatment with a strong base, to undergo either Wittig rearrangement or intramolecular attack of the benzylic anion on the oxazoline function to give products derived from cleavage of the initially formed 3-aminothienofuran products. This pattern of reactivity is directly linked to the distance between the two reactive groups as determined by X-ray diffraction, with the greatest distance in 11 leading to exclusive Wittig rearrangement, the shortest distance in 13 giving exclusively cyclisation-derived products, and the intermediate distance in 9 leading to both processes being observed. The corresponding N-butyl amides were also obtained in two cases and one of these undergoes efficient Wittig rearrangement leading to a thieno[2,3-c]pyrrolone product. Full article

Arylidene-Δ²-pyrrolin-4-ones undergo organocatalyzed double spirocyclization with 3-isothiocianato oxindoles in a domino 1,4/1,2-addition sequence. The products contain three contiguous stereocenters (ee up to 98%, dr up to 99:1, 12 examples). The absolute configuration of the major diastereomer was determined by single crystal X-ray analysis. Along with heterocyclic Michael acceptors based on oxazolone, isoxazolone, thiazolidinone, pyrazolone, and pyrimidinedione, the reported results display the applicability of unsaturated Δ²-pyrrolin-4-ones (pyrrolones) for the organocatalyzed construction of 3D-rich pyrrolone-containing heterocycles. Full article