A convenient synthesis of 4(5)-(hetero)aryl-1H-imidazoles via microwave-assisted Suzuki–Miyaura cross-coupling reaction

Efficient microwave-assisted Suzuki–Miyaura cross-coupling reaction of 3-bromo pyrazolo[1,5-a]pyrimidin-5(4H)-one: towards a new access to 3,5-diarylated 7-(trifluoromethyl)pyrazolo[1,5-a]pyrimidine derivatives

A convenient and efficient synthetic route to C3-arylated 7-trifluoromethylpyrazolo[1,5-a]pyrimidin-5-one derivatives has been reported starting from 3-bromo-7-(trifluoromethyl)pyrazolo[1,5-a]pyrimidin-5-one through a Suzuki–Miyaura cross-coupling reaction. The arylation (heteroarylation) strategy can be performed using a wide variety of aryl and heteroaryl boronic acids and requiring a tandem catalyst XPhosPdG2/XPhos to avoid the debromination reaction. These optimized conditions were successfully extended to the synthesis of 7-, 8- and 9-arylated pyrimido[1,2-b]indazol-2-ones from their corresponding brominated starting materials. Furthermore, the second C-5 arylation of C3-arylated pyrazolo[1,5-a]pyrimidin-5-ones was achieved under standard Suzuki–Miyaura cross-coupling conditions, after activating the C–O bond of the lactam function with PyBroP, giving access to a small library of 3,5-diarylated 7-(trifluoromethyl)pyrazolo[1,5-a]pyrimidines in good to excellent yields. The interest of this approach has been highlighted by the synthesis of a known anti-inflammatory agent. Additionally, a preliminary biological evaluation has revealed that a number of derivatives display micromolar IC₅₀ values against monoamine oxidase B, an important target in the field of neurodegenerative disorders.

A convenient and efficient synthetic route to C3-arylated 7-trifluoromethylpyrazolo[1,5-a]pyrimidin-5-one derivatives has been reported starting from 3-bromo-7-(trifluoromethyl)pyrazolo[1,5-a]pyrimidin-5-one through a Suzuki–Miyaura cross-coupling reaction.

Synthesis of 3-hetarylpyrroles by Suzuki–Miyaura cross-coupling

1-[tert-Butyl(diphenyl)silyl]pyrrol-3-ylboronic acid was obtained from pyrrole in three steps. Its Suzuki–Miyaura cross-coupling with functionalized pyridinyl and pyrimidinyl bromides afforded new promising 3-hetaryl-1H-pyrroles.

An Expedient Synthesis of Flexible Nucleosides through Enzymatic Glycosylation of Proximal and Distal Fleximer Bases

The structurally unique “fleximer” nucleosides were originally designed to investigate how flexibility in a nucleobase could potentially affect receptor–ligand recognition and function. Recently they have been shown to have low‐to‐sub‐micromolar levels of activity against a number of viruses, including coronaviruses, filoviruses, and flaviviruses. However, the synthesis of distal fleximers in particular has thus far been quite tedious and low yielding. As a potential solution to this issue, a series of proximal fleximer bases (flex‐bases) has been successfully coupled to both ribose and 2′‐deoxyribose sugars by using the N‐deoxyribosyltransferase II of Lactobacillus leichmannii (LlNDT) and Escherichia coli purine nucleoside phosphorylase (PNP). To explore the range of this facile approach, transglycosylation experiments on a thieno‐expanded tricyclic heterocyclic base, as well as several distal and proximal flex‐bases were performed to determine whether the corresponding fleximer nucleosides could be obtained in this fashion, thus potentially significantly shortening the route to these biologically significant compounds. The results of those studies are reported herein.

Modelling a ‘histidine brace’ motif in mononuclear copper monooxygenases

A mononuclear copper complex bearing a ‘histidine brace’ is synthesised and characterised as an active-site model of mononuclear copper monooxygenases such as lytic polysaccharide monooxygenases (LPMOs) and particulate methane monooxygenase (pMMO).

2'-Deoxyribonucleoside 5'-triphosphates bearing 4-phenyl and 4-pyrimidinyl imidazoles as DNA polymerase substrates

We developed a versatile access to a series of 4-substituted imidazole 2'-deoxynucleoside triphosphate bearing functionalized phenyl or pyrimidinyl rings. 4-Iodo-1H-imidazole was enzymatically converted into the corresponding 2'-deoxynucleoside, which was then chemically derived into its 5'-triphosphate, followed by 4-arylation via Suzuki-Miyaura coupling using (hetero)arylboronic acids. Both KF (exo-) and Deep Vent (exo-) DNA polymerases incorporated these modified nucleotides in primer-extension assays, adenine being the preferred pairing partner in the template. The 4-(3-aminophenyl)imidazole derivative (3APh) was the most efficiently inserted opposite A by KF (exo-) with only a 37-fold lower efficiency (Vmax/KM) than that of the correct dTTP. No further extension occurred after the incorporation of a single aryl-imidazole nucleotide. Interestingly, the aryl-imidazole dNTPs were found to undergo successive incorporation by calf thymus terminal deoxynucleotidyl transferase with different tailing efficiencies among this series and with a marked preference for 2APyr polymerization.

Synthesis of 4-substituted pyrazole-3,5-diamines via Suzuki-Miyaura coupling and iron-catalyzed reduction

A general and efficient synthesis of 4-substituted-1H-pyrazole-3,5-diamines was developed to access derivatives with an aryl, heteroaryl, or styryl group, which are otherwise relatively difficult to prepare. The first step is based on the Suzuki-Miyaura cross-coupling reaction utilizing the XPhos Pd G2 precatalyst. The coupling reactions of 4-bromo-3,5-dinitro-1H-pyrazole with the electron-rich/deficient or sterically demanding boronic acids enabled the production of the corresponding dinitropyrazoles. The subsequent iron-catalyzed reduction of both nitro groups with hydrazine hydrate accomplished the synthesis. The additional demethylation of the 4-methoxystyryl derivative allowed the production of the carboanalog of CAN508 reported as a selective CDK9 inhibitor.

An expedient synthesis of flexible nucleosides via a regiocontrolled enzymatic glycosylation of functionalized imidazoles

A versatile two-step synthesis of C4- and C5-arylated 2′-deoxyribosylimidazoles was elaborated by enzymaticN-transglycosylation followed by microwave-assisted Pd-catalysed arylation reactions.

Expedient and generic synthesis of imidazole nucleosides by enzymatic transglycosylation

A straightforward route to original imidazole-based nucleosides that makes use of an enzymatic N-transglycosylation step is reported in both the ribo- and deoxyribo-series. To illustrate the scope of this approach, a diverse set of 4-aryl and 4-heteroaryl-1H-imidazoles featuring variable sizes and hydrogen-bonding patterns was prepared using a microwave-assisted Suzuki-Miyaura cross-coupling reaction. These imidazole derivatives were examined as possible substrates for the nucleoside 2'-deoxyribosyltransferase from L. leichmannii and the purine nucleoside phosphorylase from E. coli. The optimum transglycosylation conditions, including the use of co-adjuvants to address solubility issues, were defined. Enzymatic conversion of 4-(hetero)arylimidazoles to 2'-deoxyribo- or ribo-nucleosides proceeded in good to high conversion yields, except bulky hydrophobic imidazole derivatives. Nucleoside deoxyribosyltransferase of class II was found to convert the widest range of functionalized imidazoles into 2'-deoxyribonucleosides and was even capable of bis-glycosylating certain heterocyclic substrates. Our findings should enable chemoenzymatic access to a large diversity of flexible nucleoside analogues as molecular probes, drug candidates and original building blocks for synthetic biology.