Comprehensive Overview of Progress in Functionalization of 2‐Pyridone and 2, 4 ‐Dihydroxy Pyridine: Key Constituents of Vital Natural Products

Synthesis of N-benzyl pyridones from para-quinone methides (p-QMs) at room temperature: evaluation of in vitro blood-stage antiplasmodial activity

We present a method for synthesizing N-benzyl pyridones from para-quinone methides (p-QMs) and 2- or 4-hydroxy pyridines in the presence of a base at room temperature. The reaction proceeds through 1,6-Michael addition reaction. Simple operation, good to excellent yields, broad substrate scope, and good functional group tolerance are the salient features of the developed methodology. The synthesized N-benzyl pyridones displayed significant in vitro blood-stage antiplasmodial activity at sub-micromolar concentration.

Co(III) or Ru(II)-Catalyzed Selective C-H Alkynylation of 2-Pyridones and Their Derivatives with Bromoalkynes

We successfully reported selective C-H alkynylation of 2-pyridones with bromoalkynes under the catalysis of Co(III) or Ru(II). The alkynylation reaction used easily accessible bromoalkynes instead of high-valent iodine alkynes. There is a broad substrate scope of 2-pyridones with good yields. In addition, 2-pyridone can be used as a weakly directing group for C-H alkynylation of the proximal aryl C-H bond. This method offers an efficient approach for synthesizing diverse 2-pyridone derivatives, yielding alkynylated products up to 95% yield (>40 examples).

Environment benign synthesis of 5-acyl-4-hydroxypyridin-2(1H)-one derivatives as antioxidant and α-amylase inhibitors

AIM

Oxidative stress, caused by postprandial activities, is a major global health issue causing chronic diseases like diabetes mellitus, cancer, and asthma. Therefore, it was envisaged to design and synthesize a series of substituted 4-hydroxypyridine-2(1 h)-ones in order to develop new molecules that can reduce oxidative stress and modulate α-amylase activity also.

MATERIALS & METHODS

An environmentally benign, solvent and catalyst free, natural product inspired synthesis of 4-hydroxypyridin-2(1 h)-one derivatives has been developed. The synthetic analogues were evaluated in vitro α-amylase activity and antioxidant potential.

RESULTS

Among all the synthesized compounds, 4a, 4c, and 4d displayed many folds higher antioxidants activity than the standard, BHT. The in vitro α-amylase inhibition was found to be moderate with IC50 values ranging from 5.48 to 9.31 mm as compared to the standard acarbose (IC50 = 0.65 mm). The most active compound against α-amylase 4c was further investigated for its binding affinity within the active site of the enzyme and the kinetics studies revealed probable uncompetitive mode of inhibition.

CONCLUSION

Compound 4a was found to be promising antioxidant and 4c as a good α-amylase inhibitor. These compounds could pave the way for development of new α-amylase inhibitors with antioxidant capabilities thereby effectively mitigating diabetes mellitus.

Solid-state synthesis of polyfunctionalized 2-pyridones and conjugated dienes

Functionalized 2-pyridones are important biologically active compounds, DNA base analogues and synthetic intermediates. Herein, we report a simple, green, solid-state synthesis of differently substituted 2-pyridones. It starts from commercially available amines and activated alkynes, uses silica gel (15%Cs2CO3/SiO2) as the solid phase and a reaction vial as the only equipment. If necessary, heating is performed in a laboratory oven. Since most reactions are completed within a few hours, no additional energy consumption is required. The syntheses do not require solvents and other reagents and are easily monitored by standard analytical techniques. The atom economy is high, since all atoms of reactants are present in the products and EtOH is the only by-product. The syntheses produce polyfunctionalized conjugated dienes as the only intermediates, which are also important building blocks.

Phenylhydrazone Alkaloids from the Deep-Sea Cold Seep Derived Fungus Talaromyces amestolkiae HDN21-0307

Alkaloids with a phenylhydrazone architecture are rarely found in nature. Four unusual phenylhydrazone alkaloids named talarohydrazones A-D (1-4) were isolated from the deep-sea cold seep derived fungus Talaromyces amestolkiae HDN21-0307 using the one strain-many compounds (OSMAC) approach and MS/MS-based molecular networking (MN) combined with network annotation propagation (NAP) and the unsupervised substructure annotation method MS2LDA. Their structures were elucidated by spectroscopic data analysis, single-crystal X-ray diffraction, and quantum chemical calculations. Talarohydrazone A (1) possessed an unusual skeleton combining 2,4-pyridinedione and phenylhydrazone. Talarohydrazone B (2) represents the first natural phenylhydrazone-bearing azadophilone. Bioactivity evaluation revealed that compound 1 exhibited cytotoxic activity against NCI-H446 cells with an IC50 value of 4.1 μM. In addition, compound 1 displayed weak antibacterial activity toward Staphylococcus aureus with an MIC value of 32 μg/mL.

Development and Scale-Up of a New Sulfone-Based Bismacycle as a Universal Precursor for Bi(V)-Mediated Electrophilic Arylation

The scope and practical utility of bismuth(V)-mediated electrophilic arylation have been greatly improved by the recent development of user-friendly protocols based on modular bismacycle reagents. Here, we report the scalable synthesis of a new bench-stable bismacycle bromide and demonstrate that it can be used as a "universal precursor" in electrophilic arylation. Relative to established syntheses of related bismacycles, the new protocol benefits from improved step- and vessel-economy, reduced production time, and the complete elimination of cryogenic temperatures and undesirable solvents (Et2O and CH2Cl2). The synthesis is complemented by a robust, chromatography-free purification procedure that was developed by using design of experiments. We show that this process is highly reproducible at the 100 mmol scale, with two independent experiments giving 61 and 62% yields of isolated material. We anticipate that this efficient method for the synthesis of a new bismacycle precursor will expedite both (a) wider uptake of existing bismuth-mediated arylation methods by the synthetic community and (b) ongoing efforts to develop new bismuth-mediated transformations.

Umpolung Synthesis of Pyridyl Ethers by BiV -Mediated O-Arylation of Pyridones

We report that O-selective arylation of 2- and 4-pyridones with arylboronic acids is affected by a modular, bismacycle-based system. The utility of this umpolung approach to pyridyl ethers, which is complementary to conventional methods based on S_N Ar or cross-coupling, is demonstrated through the concise synthesis of Ki6783 and picolinafen, and the formal synthesis of cabozantib and golvatinib. Computational investigations reveal that arylation proceeds in a concerted fashion via a 5-membered transition state. The kinetically-controlled regioselectivity for O-arylation-which is reversed relative to previous Bi^V -mediated pyridone arylations-is attributed primarily to the geometric constraints imposed by the bismacyclic scaffold.