Regioselective Base-Mediated Cyclizations of Mono-N-acylpropargylguanidines

Regioselective 5-exo-dig (halo)cyclization of N-propargyloxycarbonyl guanidine derivatives under mild conditions

A highly regioselective 5-exo-dig cyclization of aromatic N-propargyloxycarbonyl guanidines was developed via an Ag(I)-catalyzed intramolecular hydroamination reaction. This method features a fast reaction rate and mild reaction conditions. Furthermore, it was extended to access halogenated analogues via a one-pot Ag(I)-catalyzed bromocyclization reaction or an I2-mediated iodocyclization reaction with high E/Z selectivity.

Bioactivity-Driven Synthesis of the Marine Natural Product Naamidine J and Its Derivatives as Potential Tumor Immunological Agents by Inhibiting Programmed Death-Ligand 1

The total synthesis of the marine natural product naamidine J and a rapid structure modification toward its derivatives were achieved on the basis of several rounds of structure-relationship analyses of their tumor immunological activities. These compounds were tested for programmed death-ligand 1 (PD-L1) protein expression in human colorectal adenocarcinoma RKO cells. Among them, compound 11c was found to efficiently suppress constitutive PD-L1 expression in RKO cells with low toxicity and further exerted its antitumor effect in MC38 tumor-bearing C57BL/6 mice by reducing PD-L1 expression and enhancing tumor-infiltrating T-cell immunity. This research work may provide insight for the discovery of new marine natural product-derived tumor immunological drug leads.

A Cancer-Selective Zinc Ionophore Inspired by the Natural Product Naamidine A

We present data demonstrating the natural product mimic, zinaamidole A (ZNA), is a modulator of metal ion homeostasis causing cancer-selective cell death by specifically inducing cellular Zn²⁺-uptake in transformed cells. ZNA's cancer selectivity was evaluated using metastatic, patient-derived breast cancer cells, established human breast cancer cell lines, and three-dimensional organoid models derived from normal and transformed mouse mammary glands. Structural analysis of ZNA demonstrated that the compound interacts with zinc through the N²-acyl-2-aminoimidazole core. Combination treatment with ZnSO₄ strongly potentiated ZNA's cancer-specific cell death mechanism, an effect that was not observed with other transition metals. We show that Zn²⁺-dyshomeostasis induced by ZNA is unique and markedly more selective than other known Zn²⁺-interacting compounds such as clioquinol. The in vivo bioactivity of ZNA was also assessed and revealed that tumor-bearing mice treated with ZNA had improved survival outcomes. Collectively, these data demonstrate that the N²-acyl-2-aminoimidazole core of ZNA represents a powerful chemotype to induce cell death in cancer cells concurrently with a disruption in zinc homeostasis.

Reactions of secondary propargylamines with heteroallenes for the synthesis of diverse heterocycles

This focused review aims to summarize recent developments in the processes involving additions of secondary propargylamines to various heteroallenes and subsequent transition metal-catalyzed or electrophile-mediated cyclizations.