Design, synthesis and biological evaluation of paclitaxel-mimics possessing only the oxetane D-ring and side chain structures

Synthesis and Anticancer Activity of Ergosterol Peroxide Hybrids With Paclitaxel Side Chain Inducing Apoptosis in Human Hepatoma Carcinoma Cells

The antitumor activities of natural paclitaxel (PTX), semisynthetic docetaxel, and cabazitaxel are highly dependent on their C-13 side chains. Therefore, using natural ergosterol peroxide (EP, 1) as the lead compound, two EP-PTX hybrids (EP-A2 and EP-B2) were prepared and their antitumor activities were evaluated against 4 kinds of human MCF-7, HepG2, HCT-116, and A549 cell lines in vitro. The results showed that both EP-A2 and EP-B2 inhibited the growth of all four kinds of tested tumor cell lines. For paclitaxel-resistant MCF-7 cells, both EP-A2 and EP-B2 showed significant inhibitory activity with relatively low IC50 values (9.39 μM and 8.60 μM, respectively). In addition, EP-B2 inhibited the growth of the HepG2 cells (IC50 = 7.82 μM) more successfully than EP. Preliminary studies of the mechanism suggest that EP-B2 could arrest the G1 phase transition in HepG2 cells. In addition, EP-B2 showed an obvious apoptosis-inducing effect in HepG2 cells, as detected by the Annexin V/PI binding assay and the Western blot assay. Hybrid EP-B2 has the potential to become a novel antitumor drug through further study of the mechanism of action and its structural modifications.

Synthesis and biological activity evaluation of novel 3,5,7-trisubstituted pyrazolo[1,5-a]pyrimidines

Mutation of FLT3 protein kinase is often associated with deregulated cell proliferation in acute myeloid leukemia and the inhibition of this kinase is a potential therapeutic strategy. We report a novel series of 3,5,7-trisubstituted pyrazolo[1,5-a]pyrimidines prepared in an effort to study their biological activity particularly toward FLT3-ITD and its downstream regulators as well as toward CDK2 and CDK9. Derivative 10b was capable to strongly inhibit all kinases and its selectivity in FLT3-ITD expressing cell lines MOLM13 and MV4-11 was in line with FLT3-ITD inhibition. Further biochemical analyses and molecular docking confirmed FLT3 as a cellular target of 10b.

Molecular-docking-guided design, palladium-catalyzed synthesis and anticancer activity of paclitaxel-benzoxazoles hybrids

A series of new paclitaxel-benzoxazoles hybrids were designed based on both the molecular docking mode of beta-tubulin with paclitaxel derivatives (7a and 7g), and the activity-structure relationship of C-13 side chain in paclitaxel. Palladium-catalyzed direct Csp²–H arylation of benzoxazoles with different aryl-bromides was used as the key synthetic strategy for the aryl-benzoxazoles moieties in the hybrids. Twenty-six newly synthesized hybrids were screened for their antiproliferative activity against human cancer cell lines such as human breast cancer cells (MDA-MB-231) and liver hepatocellular cells (HepG2) by the MTT assay and results were compared with paclitaxel. Interestingly, most hybrids (7a–7e, 7i, 7k, 7l, 7A, 7B, 7D and 7E) showed significantly active against both cell lines at concentration of 50 µM, which indicated that the hybrid strategy is effective to get structural simplified paclitaxel analogues with high anti-tumor activity.

Selective separation and inexpensive purification of paclitaxel based on molecularly imprinted polymers modified with ternary deep eutectic solvents

Paclitaxel (PTX) is a powerful anticancer natural product, with its separation and purification having been widely studied. In this work, new molecular imprinted polymers (MIPs) using deep eutectic solvents (DESs) with different molar ratios were prepared as functional monomers. These were then used as adsorbents in solid phase extraction (SPE) for the separation of PTX from its structural analogs. The polymers were characterized by energy disperive X-rays (EDX), scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and fourier transform infrared spectroscopy (FT-IR). The results suggested that the formative regular DES-MIPs had an even pore-size distribution and a large specific surface area. The dynamic adsorption and static adsorption showed that the DES-MIPs had excellent adsorption performance, with a maximum adsorption capacity and optimum adsorption time of 87.08 mg/g and 180 min, respectively. The selective adsorption experiments showed that the material had outstanding selectivity, and the maximum selectivity factor was 6.20. For stability, after six consecutive adsorption and desorption cycles, the DES-MIPs maintained the perfect stability and reusability. Furthermore, the fabricated SPE column was successfully utilized for extracting and eluting PTX. This study provides a reliable protocol for the separation and purification PTX from its structural analogs and the DES-MIPs materials have excellent potential application value in pharmaceutical industry.

Design, Synthesis, and Anticancer Activity of Natural Product Hybrids With Paclitaxel Side Chain Inducing Apoptosis in Human Colon Cancer Cells

Based on the strong activity dependence of paclitaxel (PTX; Taxol) or docetaxel (Taxotere) on the C-13 side chain, a small library of dehydroepiandrosterone, cholesterol, vitamin D2, and alkaloids talatisamine and songorine-PTX hybrids have been synthesized and evaluated for in vitro anticancer activity by MTT assay against human breast (MCF-7), colon (HCT116), lung carcinoma (A549), and renal adenocarcinoma (786-0) cancer cell lines. Most hybrids (11b, 12b, 13b, 15b, and 18b) reduced the growth of MCF-7 and 786-0 cells with low PTX sensitivity in vitro. Among the synthesized compounds, hybrid 11b was better in inhibiting the growth of the 4 cells than PTX. A relatively low IC50 value of compound 11b (8.16 ± 0.04 μM) was also examined after exposure for 48 hours. Hybrid 11b showed a proapoptotic effect in HCT116 cells evaluated by Annexin V/propidium iodide binding assay. The level of hybrid 11b leading to protective cell death in HCT116 cells was detected using western blot and not easily observed in our basic examinations.

Palladium-Catalyzed Synthesis and Anticancer Activity of Paclitaxel-Dehydroepiandrosterone Hybrids

According to the activity-structure relationship of the C-13 side chain in paclitaxel or docetaxel, eighteen novel paclitaxel-dehydroepiandrosterone (DHEA) hybrids were designed and synthesized by Pd(II)-catalyzed Suzuki-Miyaura cross-coupling of 17-trifluoromethanesulfonic enolate-DHEA with different aryl boronic acids. The in vitro anticancer activity of the hybrids against a human liver cancer cell line (HepG-2) was evaluated by MTT assay, showing that most of these hybrids possessed moderate antiproliferative activity against the HepG-2 cancer cell line. Among these hybrids, three ones (7b, 7g, and 7i) with ortho-substituents in the phenyl group of the D-ring of DHEA analogues exhibited moderate anticancer activity. The optimal compound 7i showed superior anticancer activity against the HepG-2 cell line with an IC₅₀ value of 26.39 μM.

Polycyclic Sulfoximines as New Scaffolds for Drug Discovery

The design and synthesis of three novel polycyclic scaffolds containing sulfoximines are presented in this work, which exemplify that sulfoximines represent a real opportunity for the discovery of new drug candidates. Additionally, the structures present at least two points of diversification and contain a high level of sp³-character, hence being very interesting 3D scaffolds. The compounds synthesized were added to the compound collection of the European Lead Factory.

Recent advances in microtubule-stabilizing agents

Highly dynamic mitotic spindle microtubules are superb therapeutic targets for a group of chemically diverse and clinically successful anticancer drugs. Microtubule-targeted drugs disrupt microtubule dynamics in distinct ways, and they are primarily classified into two groups: microtubule destabilizing agents (MDAs), such as vinblastine, colchicine, and combretastatin-A4, and microtubule stabilizing agents (MSAs), such as paclitaxel and epothilones. Systematic discovery and development of new MSAs have been aided by extensive research on paclitaxel, yielding a large number of promising anticancer compounds. This review focuses on the natural sources, structural features, mechanisms of action, structure-activity relationship (SAR) and chemical synthesis of MSAs. These MSAs mainly include paclitaxel, taccalonolides, epothilones, FR182877 (cyclostreptin), dictyostatin, discodermolide, eleutherobin and sarcodictyins, zampanolide, dactylolide, laulimalides, peloruside and ceratamines from natural sources, as well as small molecular microtubule stabilizers obtained via chemical synthesis. Then we discuss the application prospect and development of these anticancer compounds.

Room-temperature palladium-catalysed Suzuki–Miyaura coupling of arylboric acid with aryl chlorides

The first room-temperature Suzuki–Miyaura coupling of aryl-boronic acid with aryl chlorides catalyzed by a Pd(OAc)₂/NiXantphos-based system is communicated.

The quest for a simple bioactive analog of paclitaxel as a potential anticancer agent

Paclitaxel (PTX), introduced into the clinic in 1991, has revealed itself as an effective antimicrotubule drug for treatment of a range of otherwise intractable cancers. Along with docetaxel (DTX) and in combination with other agents such as cisplatin, it has proven to be a first-line therapy. Unfortunately, PTX and DTX carry severe liabilities such as debilitating side effects, rapid onset of resistance, and rather complex molecular structures offering substantial challenges to ease of synthetic manipulation. Consequently, the past 15 years has witnessed many efforts to synthesize and test highly modified analogs based on intuitive structural similarity relationships with the PTX molecular skeleton, as well as efforts to mimic the conformational profile of the ligand observed in the macromolecular tubulin-PTX complex. Highly successful improvements in potency, up to 50-fold increases in IC50, have been achieved by constructing bridges between distal centers in PTX that imitate the conformer of the electron crystallographic binding pose. Much less successful have been numerous attempts to truncate PTX by replacing the baccatin core with simpler moieties to achieve PTX-like potencies and applying a wide range of flexible synthesis-based chemistries. Reported efforts, characterized by a fascinating array of baccatin substitutes, have failed to surpass the bioactivities of PTX in both microtubule disassembly assays and cytotoxicity measurements against a range of cell types. Most of the structures retain the main elements of the PTX C13 side chain, while seeking a smaller rigid bicycle as a baccatin replacement adorned with substituents to mimic the C2 benzoyl moiety and the oxetane ring. We surmise that past studies have been handicapped by solubility and membrane permeability issues, but primarily by the existence of an expansive taxane binding pocket and the discrepancy in molecular size between PTX and the pruned analogs. A number of these molecules offer molecular volumes 50-60% that of PTX, fewer contacts with the tubulin protein, severe mismatches with the PTX pharmacophore, lessened capacity to dispel binding site waters contributing to ΔGbind, and unanticipated binding poses. The latter is a critical drawback if molecular designs of simpler PTX structures are based on a perceived or known PTX binding conformation. We conclude that design and synthesis of a highly cytotoxic tubulin-assembly agent based on the paclitaxel pharmacophore remains an unsolved challenge, but one that can be overcome by focus on the architecture of the taxane binding site independent of the effective, but not unique, hand-in-glove match represented by the PTX-tubulin complex.