Photoinduced in situ generation of DNA-targeting ligands: DNA-binding and DNA-photodamaging properties of benzo[c]quinolizinium ions

• Julika Schlosser,
• Olga Fedorova,
• Yuri Fedorov and
• Heiko Ihmels

Beilstein J. Org. Chem. 2024, 20, 101–117, doi:10.3762/bjoc.20.11

• Academy of Sciences, Vavilova str. 28, 119991 Moscow, Russia 10.3762/bjoc.20.11 Abstract The photoreactions of selected styrylpyridine derivatives to the corresponding benzo[c]quinolizinium ions are described. It is shown that these reactions are more efficient in aqueous solution (97–44%) than in

• organic solvents (78–20% in MeCN). The quinolizinium derivatives bind to DNA by intercalation with binding constants of 6–11 × 104 M−1, as shown by photometric and fluorimetric titrations as well as by CD- and LD-spectroscopic analyses. These ligand–DNA complexes can also be established in situ upon

• irradiation of the styrylpyridines and formation of the intercalator directly in the presence of DNA. In addition to the DNA-binding properties, the tested benzo[c]quinolizinium derivatives also operate as photosensitizers, which induce DNA damage at relative low concentrations and short irradiation times

Cation-induced ring-opening and oxidation reaction of photoreluctant spirooxazine–quinolizinium conjugates

• Phil M. Pithan,
• Sören Steup and
• Heiko Ihmels

Beilstein J. Org. Chem. 2020, 16, 904–916, doi:10.3762/bjoc.16.82

• a certain extent Hg2+) initially induced a ring-opening reaction that was irreversibly followed by a fast ring closure–deprotonation–oxidation sequence to give styryl-substituted naphthoxazole derivatives as the products quantitatively. For the quinolizinium-substituted spirooxazine derivative, the

• +. Keywords: oxazole; oxidation; quinolizinium; spirooxazines; styryl dyes; Introduction Spiropyrans and spirooxazines are exemplary photochromic compounds that have gained great attention in the last decades because they allow to reversibly alter and control the physical and chemical properties of

• –oxidation reaction under aerobic conditions [51][52][53]. In this context, we were interested in the effect of a positively charged arylvinyl substituent on the photochromic properties of the spironaphthoxazine. For this purpose, we chose the quinolizinium ion as the cationic aryl substituent because it has

Reversible photoswitching of the DNA-binding properties of styrylquinolizinium derivatives through photochromic [2 + 2] cycloaddition and cycloreversion

• Sarah Kölsch,
• Heiko Ihmels,
• Jochen Mattay,
• Norbert Sewald and
• Brian O. Patrick

Beilstein J. Org. Chem. 2020, 16, 111–124, doi:10.3762/bjoc.16.13

• deactivation of a stilbene tyrosine kinase inhibitor by a [2 + 2] photocycloaddition [59]. As the quinolizinium ion has been established as a versatile platform for the development of DNA intercalators [60], we identified styryl-substituted quinolizinium derivatives as a promising basis for the search for

• ligands 3a–c upon association with DNA resembled the ones observed for other styryl-substituted quinolizinium derivatives [62][63][64][65][66][67]. Accordingly, the emission enhancement most likely resulted from the accommodation of the ligand in the constrained binding site of the DNA, which led to a

• particular, the weak positive LD band indicated an alignment of the aromatic units along the DNA grooves. In addition, the close vicinity of the quinolizinium substituents to the DNA helix was further confirmed by the CD band in the absorption region of the quinolizinium moiety, as it resulted from the

Identification of optimal fluorescent probes for G-quadruplex nucleic acids through systematic exploration of mono- and distyryl dye libraries

• Xiao Xie,
• Michela Zuffo,
• Marie-Paule Teulade-Fichou and
• Anton Granzhan

Beilstein J. Org. Chem. 2019, 15, 1872–1889, doi:10.3762/bjoc.15.183

• : replacement of the 2,4-pyridinium unit in dye 1a with a 2,6-pyridinium (7a) or a 2,4-quinolizinium moiety (11a) leads to a blue shift of the absorption maximum, whereas all other heterocyclic units lead to significantly stronger (10a, 14a) and/or red-shifted (9a, 12a, 13a) absorption bands (Table 1 and Figure

Synthesis of 9-arylalkynyl- and 9-aryl-substituted benzo[b]quinolizinium derivatives by Palladium-mediated cross-coupling reactions

• Siva Sankar Murthy Bandaru,
• Darinka Dzubiel,
• Heiko Ihmels,
• Mohebodin Karbasiyoun,
• Mohamed M. A. Mahmoud and
• Carola Schulzke

Beilstein J. Org. Chem. 2018, 14, 1871–1884, doi:10.3762/bjoc.14.161

• -Arylbenzo[b]quinolizinium derivatives were prepared with base-free Suzuki–Miyaura coupling reactions between benzo[b]quinolizinium-9-trifluoroborate and selected benzenediazonium salts. In addition, the Sonogashira coupling reaction between 9-iodobenzo[b]quinolizinium and the arylalkyne derivatives yielded

• four novel 9-(arylethynyl)benzo[b]quinolizinium derivatives under relatively mild reaction conditions. The 9-(N,N-dimethylaminophenylethynyl)benzo[b]quinolizinium is only very weakly emitting, but the emission intensity increases by a factor >200 upon protonation, so that this derivative may operate as

• pH-sensitive light-up probe. Photometric and fluorimetric titrations of duplex and quadruplex DNA to 9-(arylethynyl)benzo[b]quinolizinium derivatives revealed a significant binding affinity of these compounds towards both DNA forms with binding constants of Kb = 0.2–2.2 × 105 M−1. Keywords: DNA

Interactions between photoacidic 3-hydroxynaphtho[1,2-b]quinolizinium and cucurbit[7]uril: Influence on acidity in the ground and excited state

• Jonas Becher,
• Daria V. Berdnikova,
• Darinka Dzubiel,
• Heiko Ihmels and
• Phil M. Pithan

Beilstein J. Org. Chem. 2017, 13, 203–212, doi:10.3762/bjoc.13.23

• ]quinolizinium was synthesized by cyclodehydration route and its optical properties in different media were investigated. The absorption and emission spectra of this compound depend on the pH of the solution. Thus, at higher pH values the deprotonation yields a merocyanine-type dye that exhibits significantly

• , the blue-shifted fluorescence of the hydroxyquinolizinium becomes dominant only under strongly acidic conditions. In addition, it is shown that 3-hydroxynaphtho[1,2-b]quinolizinium binds to cucurbit[7]uril (CB[7]) with moderate affinity (Kb = 1.8 × 104 M−1, pH 5) and that the pKa and pKa* values of

• cavity. In contrast, if the hydroxy group of the ligand points far outside the binding pocket of CB[7] the ESPT is comparable to the one observed with the non-complexed ligand [28]. Recently, we discovered that the 8-hydroxybenzo[b]quinolizinium ion (1a, Figure 1) represents an efficient water-soluble

Synthesis and fluorosolvatochromism of 3-arylnaphtho[1,2-b]quinolizinium derivatives

• Phil M. Pithan,
• David Decker,
• Manlio Sutero Sardo,
• Giampietro Viola and
• Heiko Ihmels

Beilstein J. Org. Chem. 2016, 12, 854–862, doi:10.3762/bjoc.12.84

• Pharmacological Sciences, via Marzolo 5, 35131 Padova, Italy University of Padova, Department of Woman’s and Child’s health, 35128 Padova, Italy 10.3762/bjoc.12.84 Abstract Cationic biaryl derivatives were synthesized by Suzuki–Miyaura coupling of 3-bromonaphtho[1,2-b]quinolizinium bromide with arylboronic acids

• states. Keywords: fluorescence; heterocycles; quinolizinium; solvatochromism; Introduction Dyes that change their absorption and emission properties, especially their color, in different media are considered as helpful optical probes, because they may be applied for the characterization and

• ][12]. Along these lines, we established the annelated quinolizinium ion as a versatile platform for the investigation of cationic chemosensors, especially when the chromophore is incorporated within a donor–acceptor system [13]. In particular, we observed that biaryl-type quinolizinium derivatives

Beyond catalyst deactivation: cross-metathesis involving olefins containing N-heteroaromatics

• Kevin Lafaye,
• Cyril Bosset,
• Lionel Nicolas,
• Amandine Guérinot and
• Janine Cossy

Beilstein J. Org. Chem. 2015, 11, 2223–2241, doi:10.3762/bjoc.11.241

• pyridinium salts in the presence of the GII catalyst (Scheme 11) [47]. The formation of seven- and eight-membered rings required high dilution. Few years later, the same authors showed that it was possible to oxidize 3,4-dihydroquinolizinium salts into their quinolizinium counterparts using Pd/C at high

Cyclization of substitued 2-(2-fluorophenylazo)azines to azino[1,2-c]benzo[d][1,2,4]triazinium derivatives

• Aleksandra Jankowiak,
• Emilia Obijalska and
• Piotr Kaszynski

Beilstein J. Org. Chem. 2013, 9, 1873–1880, doi:10.3762/bjoc.9.219

• computational results. Keywords: DFT; heterocycles; mechanism; synthesis; Introduction Derivatives of benzo[c]quinolizinium [1][2][3][4] (I, X = Y = CH, Figure 1) and its di-aza analogue pyrido[2,1-c]benzo[d][1,2,4]triazinium (I, X = Y = N) belong to a class of tricyclic cations featuring general structure I