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

Laccase-mediated chemoselective C-4 arylation of 5-aminopyrazoles

Chemoselective arylation of 5-aminopyrazoles was performed through oxidative formation of orthoquinones from catechols catalyzed by Myceliophthora thermophila laccase (Novozym 51003), and subsequently nucleophilic attack of 5-aminopyrazole to the catechol intermediates. The C-4 arylated products were obtained under extremely mild conditions without the need for amine protection or halogenation of the substrates. From this method, 10 derivatives with moderate to good efficiency (42-94%) were prepared.

Polynitro-functionalized 4-phenyl-1H-pyrazoles as heat-resistant explosives

A new class of heat-resistant explosives was synthesized by coupling N-methyl-3,5-dinitropyrazole with polynitrobenzene moieties through carbon-carbon bonds. Simple Pd(0)-based Suzuki cross-coupling reactions between N-methyl-4-bromo-3,5-dinitropyrazole and 4-chloro/3-hydroxy-phenylboronic acid followed by nitration, amination and oxidation lead to the formation of C-C connected penta-nitro energetic derivatives 6 and 10. Various other energetic derivatives, such as amino (5), azido (7), nitramino (8) and energetic salts (11-14), were also explored to fine-tune their properties. All the compounds were thoroughly characterized using IR, NMR [1H, 13C{1H}], differential scanning calorimetry (DSC), elemental analysis, and HRMS studies. Compounds 5, 10 and 13 were further characterized through 15N NMR, and the crystal structures of 6 and 14 were confirmed through single-crystal X-ray diffraction studies. The physicochemical and energetic properties of all the energetic compounds were explored. Most of the synthesized compounds demonstrated high thermal stability (decomposition temperature Tdec > 250 °C), among which compounds 5 and 6 showed excellent thermal stability, having decomposition temperatures above 300 °C. The excellent thermal stability, acceptable sensitivity and good energetic properties of compounds 5, 6, 10 and 13 make them promising heat-resistant explosives. Furthermore, these compounds were found to be more thermally stable than the known N-methyl-3,5-dinitropyrazole-based and C-N coupled 3,4,5-trinitrobenzene-azole-based energetic compounds.

Synthesis and Structural Optimization of 2,7,9-Trisubstituted purin-8-ones as FLT3-ITD Inhibitors

Therapy of FLT3-positive acute myeloid leukemia still remains complicated, despite the availability of newly approved kinase inhibitors. Various strategies to avoid the reduced efficacy of therapy have been explored, including the development of dual targeting compounds, which inhibit FLT3 and another kinase necessary for the survival and proliferation of AML cells. We have designed new 2,7,9-trisubstituted 8-oxopurines as FLT3 inhibitors and report here the structure-activity relationship studies. We demonstrated that substituents at positions 7 and 9 modulate activity between CDK4 and FLT3 kinase, and the isopropyl group at position 7 substantially increased the selectivity toward FLT3 kinase, which led to the discovery of compound 15a (9-cyclopentyl-7-isopropyl-2-((4-(piperazin-1-yl)phenyl)amino)-7,9-dihydro-8H-purin-8-one). Cellular analyses in MV4-11 cells revealed inhibition of autophosphorylation of FLT3 kinase in nanomolar doses, including the suppression of downstream STAT5 and ERK1/2 phosphorylation. We also describe mechanistic studies in cell lines and activity in a mouse xenograft model in vivo.

Cyclization of arylhydrazones of cross-conjugated enynones: synthesis of luminescent styryl-1H-pyrazoles and propenyl-1H-pyrazoles

On the basis of available ethynyl vinyl ketones and arylhydrazines, the authors have developed the two-stage synthesis method for styrylpyrazoles possessing fluorescent abilities, as well as the gram-scale synthesis method for fluorescent probes.

Synthesis of 4-styrylpyrazoles and evaluation of their inhibitory effects on cyclin-dependent kinases

BACKGROUND

Cycle-regulating and transcriptional cyclin-dependent kinases (CDKs) are attractive targets in cancer drug development. Several CDK inhibitors have already been obtained or are close to regulatory approval for clinical applications.

OBJECTIVE

Phenylazopyrazole CAN508 has been described as the first selective CDK9 inhibitor with an IC50 of 350 nM. Since the azo-moiety is not a suitable functionality for drugs due to pharmacological reasons, the preparation of carbo-analogues of CAN508 with similar biological activities is desirable. The present work is focused on the synthesis of carbo-analogues similar to CAN508 and their CDK inhibition activity.

METHODS

Herein, the synthesis of 21 novel carbo analogues of CAN508 and their intermediates is reported. Subsequently, target compounds 8a - 8u were evaluated for protein kinase inhibition (CDK2/cyclin E, CDK4/cyclin D, CDK9/cyclin T) and antiproliferative activities in cell lines (K562, MCF-7, MV4-11). Moreover, the binding mode of derivative 8s in the active site of CDK9 was revealed by molecular docking.

RESULTS

Compounds 8a - 8u were obtained from key intermediate 7, which was prepared by linear synthesis involving Vilsmeier-Haack, Knoevenagel, Hunsdiecker, and Suzuki-Miyaura reactions. Styrylpyrazoles 8t and 8u were the most potent CDK9 inhibitors with IC50 values of approximately 1 µM. Molecular modelling suggested binding in the active site of CDK9 and CDK2. The flow cytometric analysis of MV4-11 cells treated with the most active styrylpyrazoles showed a significant G1-arrest.

CONCLUSION

The prepared styrylpyrazoles showed inhibition activity towards CDKs and can provide a novel chemotype of kinase inhibitors.

Styrylpyrazoles: Properties, Synthesis and Transformations

The pyrazole nucleus and its reduced forms, pyrazolines and pyrazolidine, are privileged scaffolds in medicinal chemistry due to their remarkable biological activities. A huge number of pyrazole derivatives have been studied and reported over time. This review article gives an overview of pyrazole derivatives that contain a styryl (2-arylvinyl) group linked in different positions of the pyrazole backbone. Although there are studies on the synthesis of styrylpyrazoles dating back to the 1970s and even earlier, this type of compound has rarely been studied. This timely review intends to summarize the properties, biological activity, methods of synthesis and transformation of styrylpyrazoles; thus, highlighting the interest and huge potential for application of this kind of compound.

Modification of Boc-Protected CAN508 via Acylation and Suzuki-Miyaura Coupling

The cyclin-dependent kinase inhibitor, CAN508, was protected with di-tert-butyl dicarbonate to access the amino-benzoylated pyrazoles. The bromo derivatives were further arylated by Suzuki-Miyaura coupling using the XPhos Pd G2 pre-catalyst. The coupling reaction provided generally the para-substituted benzoylpyrazoles in the higher yields than the meta-substituted ones. The Boc groups were only utilized as directing functionalities for the benzoylation step and were hydrolyzed under conditions of Suzuki-Miyaura coupling, which allowed for elimination of the additional deprotection step.