Modular Total Syntheses of the Alkaloids Discoipyrroles A and B, Potent Inhibitors of the DDR2 Signaling Pathway

Total Syntheses of Discoipyrroles A, B, and C, Three Marine Natural Products

Herein, we describe our efforts culminating in the total syntheses of discoipyrroles A, B, and C in 6, 6, and 7 steps respectively with excellent overall yield. Total syntheses of these unique natural products have been accomplished involving microwave-mediated Paal-Knorr pyrrole synthesis, Pd-catalyzed carbonylative transformation, and MoOPH (Vedejs reagent) oxidation as key reactions to construct the 1,2,3,5-tetrasubstituted pyrrole and oxidative cyclization of highly substituted pyrrole as key steps.

A Novel Ageladine A Derivative Acts as a STAT3 Inhibitor and Exhibits Potential Antitumor Effects

The Janus kinase/signal transducer and activator of the transcription 3 (JAK/STAT3) signaling pathway controls multiple biological processes, including cell survival, proliferation, and differentiation. Abnormally activated STAT3 signaling promotes tumor cell growth, proliferation, and survival, as well as tumor invasion, angiogenesis, and immunosuppression. Hence, JAK/STAT3 signaling has been considered a promising target for antitumor therapy. In this study, a number of ageladine A derivative compounds were synthesized. The most effective of these was found to be compound 25. Our results indicated that compound 25 had the greatest inhibitory effect on the STAT3 luciferase gene reporter. Molecular docking results showed that compound 25 could dock into the STAT3 SH2 structural domain. Western blot assays demonstrated that compound 25 selectively inhibited the phosphorylation of STAT3 on the Tyr705 residue, thereby reducing STAT3 downstream gene expression without affecting the expression of the upstream proteins, p-STAT1 and p-STAT5. Compound 25 also suppressed the proliferation and migration of A549 and DU145 cells. Finally, in vivo research revealed that 10 mg/kg of compound 25 effectively inhibited the growth of A549 xenograft tumors with persistent STAT3 activation without causing significant weight loss. These results clearly indicate that compound 25 could be a potential antitumor agent by inhibiting STAT3 activation.

Total Synthesis of Denigrin E and Its Oxidative Conversion into Co-occurring Metabolite Denigrin D

An unambiguous, six-step total synthesis of denigrin E (5) from anisaldehyde 22 has been achieved, confirming the structure of this marine natural product. On treatment with t-BuOOH/Mo(CO)₆, compound 5 undergoes a unique and possibly biogenetically relevant oxidative rearrangement to generate the co-occurring metabolite denigrin D (4), which is obtained in 61% yield.

A Hydroxypyrrole Approach to 2,2'-Bi(4-pyrrolin-3-ones) and Pyrrolone-Based α-Amino Esters

A high yield synthesis of 2-amino-4-pyrrolin-3-ones including 4-pyrrolin-3-one-based amino esters by the NBS- or TfCl-mediated reaction of 3-hydroxypyrroles with amines has been developed. The reaction of 3-hydroxypyrroles with triflyl chloride in the absence of amine affords 2,2'-bi(4-pyrrolin-3-ones) in excellent yields and diastereoselectivity. The relative configuration of stereocenters in these compounds can be changed from (2RS,2'RS) to (2RS,2'SR) by the action of NaH in THF, while the reverse stereoisomerization occurs in the presence of 2,5-lutidine in MeCN. Bi(4-pyrrolin-3-ones) also can be converted to 2-amino-4-pyrrolin-3-ones in excellent yields. Bi(4-pyrrolin-3-ones) and 2-amino-4-pyrrolin-3-ones were evaluated for their antiproliferative activity toward four human tumor cell lines.

The Journey of DDR1 and DDR2 Kinase Inhibitors as Rising Stars in the Fight Against Cancer

Discoidin domain receptor (DDR) is a collagen-activated receptor tyrosine kinase that plays critical roles in regulating essential cellular processes such as morphogenesis, differentiation, proliferation, adhesion, migration, invasion, and matrix remodeling. As a result, DDR dysregulation has been attributed to a variety of human cancer disorders, for instance, non-small-cell lung carcinoma (NSCLC), ovarian cancer, glioblastoma, and breast cancer, in addition to some inflammatory and neurodegenerative disorders. Since the target identification in the early 1990s to date, a lot of efforts have been devoted to the development of DDR inhibitors. From a medicinal chemistry perspective, we attempted to reveal the progress in the development of the most promising DDR1 and DDR2 small molecule inhibitors covering their design approaches, structure-activity relationship (SAR), biological activity, and selectivity.

Iterative Suzuki-Miyaura Cross-coupling/Bromo-desilylation Reaction Sequences for the Assembly of Chemically Well-defined, Acyclic Oligopyrrole/Benzenoid Hybrids Embodying Mixed Modes of Connectivity

Syntheses of a range of chemically well-defined oligopyrrole/benzenoid hybrids are described using tandem Suzuki-Miyaura cross-coupling/bromo-desilyation reaction sequences for linking borylated pyrroles, halogenated pyrroles and/or dibromobenzenes to one another. By such means, including iterative variants, a range of all α-linked, all β-linked oligopyrroles as well as certain combinations thereof have been assembled, some of them for the first time. The conductivities of iodine-treated thin films formed from certain such systems have been determined.

Total Synthesis of the Marine Alkaloid Discoipyrrole C via the MoOPH-Mediated Oxidation of a 2,3,5-Trisubstituted Pyrrole

A total synthesis of the marine alkaloid discoipyrrole C (3) is described. In the pivotal step, the 2,3,5-trisubstituted pyrrole 19 was treated with MoOPH in the presence of MeOH, and the resulting methoxylated 1,2-dihydro-3H-pyrrol-3-one 20 subjected to reaction with potassium carbonate in MeOH then trifluoroacetic acid and H₂O. This gave a mixture of target 3 and its dehydration product, and the structure of the former compound was confirmed by single-crystal X-ray analysis.

The construction of one-dimensional Pd nanoparticles/CNFs composite catalyst attached to the G-reactor@Ag and its application in Suzuki coupling reaction

CNFs-Pd attached to the inner wall of glass reactor, which was designated as G-reactor@Ag-CNFs-Pd, had been successfully constructed. The construction of G-reactor@Ag-CNFs-Pd will make a good contribution to design heterogeneous catalyst.