Pyrrole-containing hybrids as potential anticancer agents: An insight into current developments and structure-activity relationships

Base-Mediated Synthesis of Polysubstituted Pyrroles from N-Allyl Ketimines and Alkynes: Interplay of Carbanions

Terminal (het)arylacetylenes react (KOBut/DMSO, 60 °C, 1 h) with N-allyl ketimines to afford 2-(het)aryl-4-(het)arylmetyl-5-ethylpyrroles in up to 71% yield as a result of the interaction of acetylenic and azadienic carbanions with C=N and C≡C bonds. This new reaction opens a one-pot access to synthetically and pharmaceutically prospective compounds.

Quantum Chemical Studies on the Prototropic and Acid/Base Equilibria for 2-Aminopyrrole in Vacuo-Role of CH Tautomers in the Design of Strong Brønsted Imino N-Bases

In the quest of the pivotal origin of the very strong gas-phase proton basicity for some iminopyrrole derivatives, proposed in the literature on the basis of quantum chemical calculations, the full tautomeric and acid/base equilibria were investigated in vacuo for 2-aminopyrrole exhibiting enamino-imino tautomerism. Thermochemistry of these processes investigated at the Density Functional Theory (DFT) level indicates a lower stability for the imino than for the enamino tautomers. However, the imino N atom in the imino forms displays an exceptionally high basicity, particularly in the minor and rare tautomers containing at least one tautomeric proton at the pyrrole C atom. This explains why derivatives of CH tautomers (being free of prototropy) display exceptionally high gas-phase proton basicity. As predicted by the Maksić group using quantum chemical methods, these derivatives can be considered as good organic imino N-superbase candidates. Unfortunately, some other structures of iminopyrrole derivatives (proposed by the same group) possess labile protons, and, thus, exhibit prototropy, resulting in the transformation into the more stable but less basic aminopyrrole derivatives under synthesis conditions or acid/base equilibria measurements.

Ligand-Controlled C2- or C3-Selectivity Switching in the Palladium-Catalyzed C-H Arylation of Nonsubstituted 1H-Pyrrole

The C2- or C3-selective direct C-H arylation of nonsubstituted 1H-pyrrole with aryl chlorides/nonaflates was achieved using catalysts derived from palladium and appropriate phosphine ligands. The site selectivity of the arylation can be switched by changing the ligands, and the C3-selective arylation of nonsubstituted 1H-pyrrole was realized for the first time. tBuOLi played an important role in suppressing N-arylation and accelerating C2- or C3-arylation.

Synthesis, Cytotoxicity and Antiproliferative Effect of New Pyrrole Hydrazones

Novel pyrrole-based carbohydrazide (1) and hydrazones (1A-D) were synthesized, characterized, and subjected to spectroscopic studies. The hydrazones were obtained by reacting a pyrrole hydrazide with substituted pyrrole aldehydes. The initial carbohydrazide was prepared by selective hydrazinolysis of the obtained N-pyrrolylcarboxylic acid ethyl ester. The biological activity of the newly synthesized compounds was investigated in vitro on a panel of tumor and non-tumor cell lines. Mouse embryonic fibroblasts BALB 3T3 clone A31 were used in the safety test (BALB 3T3 NRU-assay). Antiproliferative activity was determined on keratinocytes (HaCaT) and melanoma (SH-4) cells by MTT dye reduction assay. The safety test of the compounds showed low cytotoxicity and absence of phototoxic potential. Among our novel pyrrole hydrazones, 1C was the most selective (SI = 3.83) in human melanoma cells and exhibited very good antiproliferative activity (IC50 = 44.63 ± 3.51 μM). The cytotoxic effect of 1C correlates with its ability to induce apoptosis and to cause cell cycle arrest in the S phase. In addition, the results show that hydrazones obtained by condensation with β-aldehydes are more bioactive than those obtained by condensation with α-aldehydes.

Discovery of pyrrolo[2,3-d]pyrimidin-4-one derivative YCH3124 as a potent USP7 inhibitor for cancer therapy

USP7 is one of the most studied deubiquitinating enzymes, which is involved in the regulation of multiple cell signaling pathways and has been shown to be associated with the occurrence and progression of a variety of cancers. Inhibitors targeting USP7 have been studied by several teams, but most of them lack selectivity and have low activities. Herein, we reported a serious of pyrrole[2,3-d]pyrimidin-4-one derivatives through scaffold hopping of recently reported 4-hydroxypiperidine compounds. The representative compound Z33 (YCH3124) exhibited highly potent USP7 inhibition activity as well as anti-proliferative activity against four kinds of cancer cell lines. Further study revealed that YCH3124 effectively inhibited the downstream USP7 pathway and resulted in the accumulation of both p53 and p21 in a dose-dependent manner. Notably, YCH3124 disrupted cell cycle progression through restricting G1 phase and induced significant apoptosis in CHP-212 cells. In summary, our efforts provided a series of novel pyrrole[2,3-d]pyrimidin-4-one analogs as potent USP7 inhibitors with excellent anti-cancer activity.