Direct Conversion of Carboxylic Acids to Various Nitrogen-Containing Compounds in the One-Pot Exploiting Curtius Rearrangement

Design, synthesis, and anti-cancer evaluation of C-14 arylcarbamate derivatives of andrographolide

In this study, we explored a concise and mild synthetic route to produce novel C-14 arylcarbamate derivatives of andrographolide, a known anti-inflammatory and anticancer natural product. Upon assessing their anti-cancer efficacy against pancreatic ductal adenocarcinoma (PDAC) cells, some derivatives showed stronger cytotoxicity against PANC-1 cells than andrographolide. In addition, we demonstrated one derivative, compound 3m, effectively reduced the expression of oncogenic p53 mutant proteins (p53R273H and p53R248W), proliferation, and migration in PDAC lines, PANC-1 and MIA PaCa-2. Accordingly, the novel derivative holds promise as an anti-cancer agent against pancreatic cancer. In summary, our study broadens the derivative library of andrographolide and develops an arylcarbamate derivative of andrographolide with promising anticancer activity against PDAC.

1-[2-(1H-Pyrrole-2-carbonyl)phenyl]-3-(4-methoxyphenyl)urea

For the synthesis of 1-(2-(1H-pyrrole-2-carbonyl)phenyl)-3-(4-methoxyphenyl)urea, the final product, two different methods were used, in one or two steps, from (2-aminophenyl)(1H-pyrrol-2-yl)methanone. The one-step synthesis entailed a carbonylation reaction with 1/3 equivalent of triphosgene in the presence of two equivalents of trimethylamine, followed by the addition of 4-methoxyaniline to the in situ generated aryl isocyanate. The two-step synthesis required first the preparation of phenyl(2-(1H-pyrrole-2-carbonyl)phenyl)carbamate and then a substitution reaction by 4-methoxyaniline. The first method produced the final product in 72% yield, which was the best yield. The structure of the final product was confirmed by FTIR, UV-VIS, 1H and 13C NMR spectroscopy and high resolution mass spectrometry.

Reaction of Amide and Sodium Azide for the Synthesis of Acyl Azide, Urea, and Iminophosphorane

Amides reacted with NaN₃ to give the acyl azides in DMF at 25 °C and produce the symmetrical ureas in THF/H₂O at 80 °C via the sequential reaction of acyl substitution and Curtius rearrangement. All acyl azides were also obtained from the secondary amides via sequential reaction of p-toluenesulfonyl chloride and NaN₃. In addition, keto-stabilized iminophosphoranes were prepared from a one-pot reaction of amides, NaN₃, and phosphines.

TCT-mediated click chemistry for the synthesis of nitrogen-containing functionalities: conversion of carboxylic acids to carbamides, carbamates, carbamothioates, amides and amines

Here, we report a s-trichlorotriazine (TCT, also known as cyanuric chloride) mediated one-pot general method for the conversion of carboxylic acids into ubiquitous functionalities such as carbamides, carbamates, carbamothioates, amides, and amines. The TCT-mediated activation of acids followed by azidation and heating led to the isocyanate formation via Curtius rearrangement which involves click chemistry in the presence of nucleophiles and provided the coupled product. The TCT was employed at ≤40 mol% with respect to the starting materials; however, its bulk availability and low cost provide a unique opportunity towards its applicability in the synthesis of functional molecules. The optimized conditions have also been successfully demonstrated for gram scale synthesis and late-stage functionalization of natural products and drugs such as podophyllotoxin, eugenol, diosgenin, geraniol and fluvoxamine.

Investigation of Direct and Retro Chromone-2-Carboxamides Based Analogs of Pseudomonas aeruginosa Quorum Sensing Signal as New Anti-Biofilm Agents

Biofilm formation is considered a major cause of therapeutic failure because bacteria in biofilms have higher protection against antimicrobials. Thus, biofilm-related infections are extremely challenging to treat and pose major concerns for public health, along with huge economic impacts. Pseudomonas aeruginosa, in particular, is a “critical priority” pathogen, responsible for severe infections, especially in cystic fibrosis patients because of its capacity to form resistant biofilms. Therefore, new therapeutic approaches are needed to complete the pipeline of molecules offering new targets and modes of action. Biofilm formation is mainly controlled by Quorum Sensing (QS), a communication system based on signaling molecules. In the present study, we employed a molecular docking approach (Autodock Vina) to assess two series of chromones-based compounds as possible ligands for PqsR, a LuxR-type receptor. Most compounds showed good predicted affinities for PqsR, higher than the PQS native ligand. Encouraged by these docking results, we synthesized a library of 34 direct and 25 retro chromone carboxamides using two optimized routes from 2-chromone carboxylic acid as starting material for both series. We evaluated the synthesized carboxamides for their ability to inhibit the biofilm formation of P. aeruginosa in vitro. Overall, results showed several chromone 2-carboxamides of the retro series are potent inhibitors of the formation of P. aeruginosa biofilms (16/25 compound with % inhibition ≥ 50% at 50 μM), without cytotoxicity on Vero cells (IC50 > 1.0 mM). The 2,4-dinitro-N-(4-oxo-4H-chromen-2-yl) benzamide (6n) was the most promising antibiofilm compound, with potential for hit to lead optimization.

Investigation of Masked N-Acyl-N-isocyanates: Support for Oxadiazolones as Blocked N-Isocyanate Precursors

In contrast to carbon-substituted isocyanates that are common building blocks, N-substituted isocyanates remain underdeveloped and reports on their N-acyl derivatives (i. e. amido-isocyanates) are exceedingly rare. Herein, amido-isocyanates were investigated in the context of syntheses of aza-tripeptide and hydantoins subunits starting from simple bench-stable precursors. A key finding is that the amido-isocyanate formed in situ cyclized to yield an oxadiazolone, and that under suitable reaction conditions this heterocycle is a traceless blocked (masked) N-isocyanate. Using organic bases as catalysts and upon heating, oxadiazolone formation is observed, and various nucleophiles to provide the desired aza-dipeptides or hydantoins in moderate to high yields. Further support for an amido-isocyanate intermediate was obtained using carboxylic acids as nucleophiles, affording N-acylhydrazide products.

Catalytic and non-catalytic amidation of carboxylic acid substrates

The present review offers an apt summary of amide bond formation with carboxylic acid substrates by taking advantage of several methods. Carboxamides can be regarded as a substantial part of organic and medicinal chemistry due to their utility in synthesizing peptides, lactams, and more than 25% of familiar drugs. Moreover, they play a leading role in the synthesis of bioactive products with anticancer, antifungal, and antibacterial properties. The data are arranged based on the type and amount of reagents used to conduct amidation and are also divided into the following categories: catalytic amidation of carboxylic acids, non-catalytic amidation, and transamidation.

Searching for Small Molecules as Antibacterials: Non-Cytotoxic Diarylureas Analogues of Triclocarban

Triclocarban (TCC), a broad-spectrum lipophilic antimicrobial agent, is a diarylurea derivative that has been used for more than 60 years as a major ingredient of toys, clothing, food packaging materials, food industry floors, medical supplies and especially of personal care products, such as soaps, toothpaste and shampoo. In September 2016, the U.S. FDA banned nineteen antimicrobial ingredients, including TCC, in over-the-counter consumer antiseptic wash products, due to their toxicity. Withdrawal of TCC has prompted efforts to search for new antimicrobial compounds. In this paper, we present the synthesis and biological evaluation, as antibiotic and non-cytotoxic agents, of a series of diarylureas, analogues of TCC. These compounds are characterized by an intriguingly simple chemistry and can be easily synthesized. Among the synthesized compounds, 1ab and 1bc emerge as the most interesting compounds as they show the same activity of TCC (MIC = 16 µg/mL) against Staphylococcus aureus, and a higher activity than TCC against Enterococcus faecalis (MIC = 32 µg/mL versus MIC = 64 µg/mL). Moreover, 1ab and 1bc show no cytotoxicity towards the human mammary epithelial cells MCF-10A and embryonic kidney epithelial cells Hek-293, in opposition to TCC, which exhibits a marked cytotoxicity on the same cell lines and shows a good antitumor activity on a panel of cell lines tested.

Synthesis and biological evaluation of diaryl urea derivatives designed as potential anticarcinoma agents using de novo structure-based lead optimization approach

To develop inhibitors blocking VEGFR2 and the Raf/MEK/ERK mitogen-activated protein kinase signaling pathway new compounds based on sorafenib were designed, synthesized and biologically evaluated. Using de novo design method, a library of new ligands was generated and expanded. Considering in silico binding affinity towards VEGFR2, synthetic feasibility, and drug-likeness property, some of the designed ligands were selected for synthesis and screening for their in vitro antiproliferative activities against two cancer cell lines (HT-29 and A549). Four compounds (13a, 14a, 14l and 15b) exhibited stronger antiproliferative activity (with IC₅₀ values of 13.27, 6.62, 12.74, 3.38 μM, respectively) against HT-29 cells compared to that of the positive reference drug sorafenib (IC₅₀ = 17.28 μM). Notably, compound 15b demonstrated the highest activity, and in particular, it induced HT-29 apoptosis, increased intracellular reactive oxygen species level, arrested cell cycle at G0/G1 phase, and influenced the expression of apoptosis- and cell cycle-related proteins. 15b compound can effectively block the Raf/MEK/ERK pathway and inhibit VEGFR2 phosphorylation. Molecular docking revealed that 15b can bind well to the active site of VEGFR2 receptor. Collectively, 15b may be considered as a promising compound amenable for further investigation for the development of new anticancer agents.

Regorafenib analogues and their ferrocenic counterparts: synthesis and biological evaluation

New ferrocene analogues of regorafenib have been prepared and their biological activity was evaluated in kinase and cellular assays.