Metal‐Free Synthesis of Thermally Stable Fluorescent p ‐Terphenyls by Ring Transformation of 2 H ‐Pyran‐2‐ones

A terphenyl derivative-based colorimetric-fluorimetric probe for the detection of lysine and arginine and their bioimaging

Lysine (Lys) and arginine (Arg) play a crucial role in the human diets, medical diagnostics, and functional biomaterial synthesis. The imbalance of intake for these two amino acids causes various diseases. Although many analytical techniques have been reported for the detection of amino acids, there are still some issues such as the need for bulky instruments, professional operators, sensitivity to be improved, and real-time detection. Here, a novel colorimetric-fluorimetric probe based on a terphenyl derivative (TPT) has been synthesized for the precise detection of Lys and Arg. In the EtOH-H2O solution of TPT, the NH2 group at the chain end of Lys/Arg undergoes a nucleophilic addition reaction with CN groups of benzothiazole groups of the probe TPT, which breaks the initial long-conjugated system of the probe molecule. As a result, blue shifts can be observed for both UV-vis absorption spectra and fluorescence spectra, accompanying with color changes of the TPT solution. The UV-vis absorption peak of TPT solution shifts from ∼410 nm to ∼325 nm, and the solution color changes from light-yellow to colorless. The fluorescence emission shifts from ∼580 nm to ∼470 nm and the bright-yellow TPT solution changes to blue under the irradiation of 365 nm UV light. For colorimetric method, the limits of detection (LoD) are 0.82 μM and 0.90 μM for Lys and Arg, respectively. For fluorimetric method, they are 2.02 nM and 1.62 nM for Lys and Arg, respectively. In addition, TPT has good selectivity and anti-interference for Lys and Arg. The synthesized probe TPT has been successfully used for the precise detection of Lys and Arg in drugs and for fluorescence imaging of living cells. This work demonstrates that terphenyl-based derivatives are promising organic probes for the detection of Lys and Arg, providing a new way for designing other amino acids probes.

Triflic acid-promoted Friedel-Crafts-type carbocyclization of alkenylated biphenyl derivatives: Synthesis and photophysical studies of novel 9,10-dihydrophenanthrenes

An efficient metal-free, triflic acid-promoted intramolecular Friedel-Crafts-type carbocyclization of alkenylated biphenyl derivatives is discussed. This method provides an elegant route for the construction of 9,10-dihydrophenanthrenes of biological significance in good to excellent yields. The carbocyclization reaction is likely to proceeds via activation of terminal C[bond, double bond]C bond of alkenylated biphenyl derivatives followed by subsequent aromatic electrophilic substitution to give desired carbocyclic products. Single crystal X-ray diffraction analysis of compound 10d revealed that the crystals are packed in AB-AB layer packing, where the molecules are aligned in anti-parallel fashion. Notably, all of the synthesized 9,10-dihydrophenanthrenes exhibited blue to greenish yellow fluorescence with λ max = 418-481 nm range. The stokes shift, quantum yield and optical band gap of tricyclic products were computed using their absorption and emission spectra. A significant positive solvatochromic effect was observed for 9,10-dihydrophenanthrene derivative 10l, which is a characteristic of ICT interactions.

Investigation of Pharmaceutical Importance of 2H-Pyran-2-One Analogues via Computational Approaches

Highly functionalized spirocyclic ketals were synthesized through asymmetric oxidative spirocyclization via carbanion-induced ring transformation of 2H-pyran-2-ones with 1,4-cyclohexandione monoethyleneketal under alkaline conditions. Further acidic-hydrolysis of obtained spirocyclic ketals yields highly substituted 2-tetralone in good yield. Computational analysis based on the DFT calculations and MD simulations has been performed in order to predict and understand global and local reactivity properties of newly synthesized derivatives. DFT calculations covered fundamental reactivity descriptors such as molecular electrostatic potential and average local ionization energies. Nitrogen atom and benzene rings have been recognized as the most important molecular sites from these aspects. Additionally, to predict whether studied compounds are stable towards the autoxidation mechanism, we have also studied the bond dissociation energies for hydrogen abstraction and identified the derivative which might form potentially genotoxic impurities. Interactions with water, including both global and local aspects, have been covered thanks to the MD simulations and calculations of interaction energies with water, counting of formed hydrogen interactions, and radial distribution functions. MD simulations were also used to identify which excipient could be used together with these compounds, and it has been established that the polyvinylpyrrolidone polymer could be highly compatible with these compounds, from the aspect of calculated solubility parameters.