Correction: Turn-on fluorogenic sensors based on an anthraquinone signaling unit for the detection of Zn(II) and Cd(II) ions

Correction for 'Turn-on fluorogenic sensors based on an anthraquinone signaling unit for the detection of Zn(II) and Cd(II) ions' by Chawanakorn Kongsak et al., Org. Biomol. Chem., 2023, 21, 7367-7381, https://doi.org/10.1039/D3OB01223A.

Turn-on fluorogenic sensors based on an anthraquinone signaling unit for the detection of Zn(II) and Cd(II) ions

Turn-on fluorescent chemosensors based on an anthraquinone moiety, N,N'-(9,10-dioxo-9,10-dihydroanthracene-1,8-diyl)bis(2-(bis(pyridin-2-ylmethyl)amino)acetamide) (1) and N,N'-(9,10-dioxo-9,10-dihydroanthracene-2,6-diyl)bis(2-(bis(pyridin-2-ylmethyl)amino)acetamide) (2), have been successfully synthesized with the overall yields of 61% and 90%, respectively. The structures of both chemosensors 1 and 2 were elucidated using several spectroscopic techniques such as 1H NMR, 13C NMR, 2D-NMR, FTIR and HRMS. The target chemosensor 1 is a promising tool for the detection of trace levels of d10 metal ions, such as Zn(II) and Cd(II) ions, by exhibiting a significant fluorescence enhancement via a turn-on photoinduced electron transfer (PET) mechanism with a rapid and highly reproducible signal, and low detection limit values of 0.408 μM and 0.246 μM, for Zn(II) and Cd(II), respectively.

Discovery of Natural Bisbenzylisoquinoline Analogs from the Library of Thai Traditional Plants as SARS-CoV-2 3CLPro Inhibitors: In Silico Molecular Docking, Molecular Dynamics, and In Vitro Enzymatic Activity

The emergence of SARS-CoV-2 in December 2019 has become a global issue due to the continuous upsurge in patients and the lack of drug efficacy for treatment. SARS-CoV-2 3CL^Pro is one of the most intriguing biomolecular targets among scientists worldwide for developing antiviral drugs due to its relevance in viral replication and transcription. Herein, we utilized computer-assisted drug screening to investigate 326 natural products from Thai traditional plants using structure-based virtual screening against SARS-CoV-2 3CL^Pro. Following the virtual screening, the top 15 compounds based on binding energy and their interactions with key amino acid Cys145 were obtained. Subsequently, they were further evaluated for protein-ligand complex stability via molecular dynamics simulation and binding free energy calculation using molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) approaches. Following drug-likeness and ADME/Tox assessments, seven bisbenzylisoquinolines were obtained, including neferine (3), liensinine (4), isoliensinine (5), dinklacorine (8), tiliacorinine (13), 2'-nortiliacorinine (14), and yanangcorinine (15). These compounds computationally showed a higher binding affinity than native N3 and GC-373 inhibitors and attained stable interactions on the active site of 3CL^pro during 100 ns in molecular dynamics (MD) simulation. Moreover, the in vitro enzymatic assay showed that most bisbenzylisoquinolines could experimentally inhibit SARS-CoV-2 3CL^Pro. To our delight, isoliensinine (5) isolated from Nelumbo nucifera demonstrated the highest inhibition of protease activity with the IC₅₀ value of 29.93 μM with low toxicity on Vero cells. Our findings suggested that bisbenzylisoquinoline scaffolds could be potentially used as an in vivo model for the development of effective anti-SARS-CoV-2 drugs.

Scalable and Room-Temperature Ring-Opening Polymerization of ε-Caprolactone Catalyzed by Active Lithium Tetramethylene-Tethered Bis[N-(N'-butylimidazol-2-ylidene)] N-Heterocyclic Carbene as a Lewis Acid Organocatalyst

The Lewis acid organocatalytic system of lithium tetramethylene-tethered bis[N-(N'-butylimidazol-2-ylidene)] N-heterocyclic carbene (1,4-bisNHC) including lithium benzyloxide and benzyl alcohol has been successfully utilized in the ring-opening polymerization (ROP) of ε-caprolactone (CL) for the first time. The catalytic performance of this organic catalyst in the synthesis of high-molecular-weight polymers was investigated via bulk polymerization using different combinations of tetramethylene-tethered bis[N-(N'-butylimidazolium)] hexafluorophosphate (1,4-bis[Bim][PF₆]), benzyl alcohol (BnOH), and n-butyl lithium (nBuLi) ([1,4-bis[Bim][PF₆]]/[BnOH]/[nBuLi]) with the molar ratios of 0:2:2, 1:1:3, 1:2:3, and 1:2:4. The results showed that the molar ratio of 1:2:3 efficiently and rapidly initiated the bulk ROP of CL at room temperature with a high molar ratio of CL to 1,4-bis[Bim][PF₆] of 3000/1 and produced the highest number of average-molecular-weight (M_n) poly(ε-caprolactone) (103,057 g mol^-1) with the dispersity (D̵) and %conversion of 1.73 and 98% in a short period of time (152 s). From comparative studies, the relative polymerization rates of the bulk ROP of CL with different [1,4-bis[Bim][PF₆]]/[BnOH]/[nBuLi] molar ratios was determined in the following order: 1:2:4 > 1:1:3 > 1:2:3 > 0:2:2. For mechanistic investigation, the bulk ROP mechanism of CL with our organic catalyst was proposed through the intramolecular bis-lithium-carbene interaction pathway for 1,4-bisNHC_1,1,3, 1,4-bisNHC_1,2,3, and 1,4-bisNHC_1,2,4 systems.

Krabasinolide A with anti-HIVs activity from the leaves and twigs of Croton krabas

One new clerodane-type diterpenoid, together with one known, was isolated from the leaves and twigs of C. krabas. The structures of these compounds were elucidated as krabasinolide A (1) and taraxerol (2) by spectroscopic methods (UV, IR, HRESIMS, 1 D, and 2 D NMR), and the relative stereochemistry was confirmed by X-ray diffraction analysis with graphite monochromated Mo-Kα (λ = 0.71073 Å) radiation at 296(2) K. Extracts and compounds 1-2 were evaluated for in vitro antiviral activity.

Organocatalytic Ring-Opening Polymerization of ε-Caprolactone Using bis(N-(N'-butylimidazolium)alkane Dicationic Ionic Liquids as the Metal-Free Catalysts: Polymer Synthesis, Kinetics and DFT Mechanistic Study

In this work, we successfully synthesized high thermal stable 1,n-bis(N-(N′-butylimidazolium)alkane bishexafluorophosphates (1,n-bis[Bim][PF₆], n = 4, 6, 8, and 10) catalysts in 55–70% yields from imidazole which were applied as non-toxic DILs catalysts with 1-butanol as initiator for the bulk ROP of ε-caprolactone (CL) in the varied ratio of CL/nBuOH/1,4-bis[Bim][PF₆] from 200/1.0/0.25–4.0 to 700/1.0/0.25–4.0 by mol%. The result found that the optimal ratio of CL/nBuOH/1,4-bis[Bim][PF₆] 400/1.0/0.5 mol% at 120 °C for 72 h led to the polymerization conversions higher than 95%, with the molecular weight (M_w) of PCL 20,130 g mol⁻¹ (Đ~1.80). The polymerization rate of CL increased with the decreasing linker chain length of ionic liquids. Moreover, the mechanistic study was investigated by DFT using B3LYP (6–31G(d,p)) as basis set. The most plausible mechanism included the stepwise and coordination insertion in which the alkoxide insertion step is the rate-determining step.

Synthesis and application of methyl itaconate-anthracene adducts in configuration assignment of chiral secondary alcohols by 1H NMR

Novel chiral derivatising agents (CDAs) such as methyl itaconate-anthracene adducts (MIAs) were reported for the absolute configuration determination of chiral secondary alcohols by the ¹H NMR technique. These adducts were facilely prepared through well-known reactions, and furthermore, commercially available starting materials. According to these synthetic routes, the desired MIAs were afforded in 6 steps with 49% overall yield from dimethyl itaconate. Moreover, the represented MIAs provided significantly large differences of chemical shift values (Δδ^SR). No racemisation from the tertiary characteristics of the adjacent alpha carbon was observed.

Correction: Synthesis and application of methyl itaconate-anthracene adducts in configuration assignment of chiral secondary alcohols by 1H NMR

Correction for 'Synthesis and application of methyl itaconate-anthracene adducts in configuration assignment of chiral secondary alcohols by ¹H NMR' by Puracheth Rithchumpon et al., Org. Biomol. Chem., 2021, DOI: 10.1039/D1OB01387D.

Synthesis, cytotoxicity evaluation and molecular docking studies on 2',4'-dihydroxy-6'-methoxy-3',5'-dimethylchalcone derivatives

2′,4′-Dihydroxy-6′-methoxy-3′,5′-dimethylchalcone (DMC, 1) was isolated from seeds of Syzygium nervosum A.Cunn. ex DC. exhibiting intriguing biological activities. Herein, thirty three DMC derivatives including 4′-O-monosubstituted-DMC (2), 7-O-acylated-4-hydroxycoumarin derivatives (3), stilbene–coumarin derivatives (4), 2′,4′-disubstituted-DMC (5), and flavanone derivatives (6), were synthesised through acylation, alkylations, and sulfonylation. These semi-synthetic DMC derivatives were evaluated for in vitro cytotoxicity against six carcinoma cell lines. It was found that most derivatives exhibited higher cytotoxicity than DMC. In particular, 4′-O-caproylated-DMC (2b) and 4′-O-methylated-DMC (2g) displayed the strongest cytotoxicity against SH-SY5Y with IC₅₀ values of 5.20 and 7.52 μM, respectively. Additionally, 4′-O-benzylated-DMC (2h) demonstrated the strongest cytotoxicity against A-549 and FaDu with IC₅₀ values of 9.99 and 13.98 μM, respectively. Our structure–activity relationship (SAR) highlights the importance of 2′-OH and the derivatisation pattern of 4′-OH. Furthermore, molecular docking simulation studies shed further light on how these bioactive compounds interact with cyclin-dependent kinase 2 (CDK2).

Semi-synthetic DMC derivatives were synthesised and displayed biological potency against various cancer cell lines.

Synthesis and characterization of novel chiral derivatizing agents containing β-keto-anthracene adducts (KAAs) by 1H-NMR: aromatic influence and chiral alcohol absolute configuration determination

New chiral derivatizing agents and the effect of aromatic rings were investigated for absolute configuration of chiral alcohols via¹H-NMR.