Examining advances in the class of natural and non-natural piperidine azasugars, important therapeutic agents and potent glycosidase inhibitors, this review looks at syntheses applying olefin metathesis as a highly efficient key step and gateway strategy for discovery of better iminosugar leads for treatment of widespread affections like viral and metabolic diseases. Amply illustrated is how ring-closing metathesis (RCM and RCEYM), promoted by commercial ruthenium alkylidene catalysts, manage to construct the common tetrahydropyridine core while cross-metathesis (CM), starting from this generic scaffold, provides general access to families of novel azasugars. Special consideration is given to high-profile iminosugar drugs of this class (1-deoxynojirimycin and congeners, adenophorine, fagomine, isofagomine and some of their N- and C-substituted analogues) stressing upon newest trends for enhancing biological activity and modulating previously unexploited targets in multispecific therapies.

Recent trends in Ru complex chemistry are surveyed with emphasis on the development of anticancer drugs and applications in catalysis, polymers, materials science and nanotechnology.

We report straightforward access to two new anionic porous organic polymers (Si-POPs) based on hexacoordinate [SiO₆]^2– species and polyimine aromatic linkers which exhibit outstanding capabilities for removal of cationic dyes from contaminated industrial water. These multifunctional materials are stable under air and in water; they were synthesized via solvothermal chemistry exploiting Schiff base formation between tri(protocatechuic aldehyde)-silicate and 4,4′-diaminobiphenyl acid (for Si-POP-1) or 4,4′-diamino-2,2′-stilbenedisulfonic acid (for Si-POP-2). Charge neutrality of the Si-POPs was achieved by [Et₃NH]⁺ cations. The structures were determined by spectroscopic techniques (FT-IR and solid ¹³C-NMR spectroscopy), while SEM and TEM revealed a micrometer-scale solid sphere morphology for Si-POP-1 and hollow nanometer-sized tubes for Si-POP-2. BET specific surface area determination gave 376 and 234 m² g⁻¹ for Si-POP-1 and Si-POP-2, respectively. The unprecedented adsorption abilities of these materials for standard cationic dyes such as methylene blue (MB), malachite green (MG), and Basic Blue 7 (BB7) were revealed by studying the effects of system variables such as pH, contact time, temperature and mixed-dye solutions. At 25 °C, the maximum adsorption capacity of Si-POP-1 reached 300.3 mg g⁻¹ for MB and 378.5 mg g⁻¹ for MG, while the performance of Si-POP-2 at the same temperature was substantially higher (3516 mg g⁻¹ for MB and 662 mg g⁻¹ for MG). Furthermore, at 35 °C, the maximum adsorption of MB on Si-POP-2 reached 4098 mg g⁻¹, surpassing the performance of previous adsorbents. It was found that both Si-POP-1 and Si-POP-2 exhibit charge and size-selective adsorption. Thermodynamics studies indicated that the adsorptions were spontaneous and endothermic. A minimal loss of adsorptive capacity of Si-POP-2 (less than 4%) was observed after four cycles, demonstrating an effective reuse of the regenerated POP in discarding MB from effluents. Importantly, this green protocol also allows recovery of the dye retained in the POP. These assets recommend these new hexacoordinate silicate-based adsorbents as viable materials for wastewater remediation by removal of organic dye pollutants affecting nature and public health.

The generation of hydrogen-based energy and environmental remediation using sunlight is an emerging topic of great significance for meeting the ever-growing global need. However, the actual photocatalytic performance is still far below expectations because of the relatively slack charge-carrier separation and migration as well as insufficient spectral absorption in semiconductors. Therefore, the rational construction of heterojunctions is considered as an effective approach to solving the above issues. In this context, we have, for the first time, designed and synthesized a two-dimensional 2D-on-2D heterostructure, based on 2D Ag-doped ZnIn₂S₄ nanoplates deposited on 2D g-C₃N₄ nanosheets (denoted as g-C₃N₄/Ag:ZnIn₂S₄). This construct benefits from improved visible-light absorption by unveiling a greater number of catalytically active sites, effectively enhancing charge-carrier separation and relocation. Detailed analysis has proved that under visible-light irradiation, the optimized g-C₃N₄/20 wt% Ag:ZnIn₂S₄ nanocomposite has substantially upgraded photocatalytic activity in hydrogen formation by water splitting (hydrogen evolution rate of up to 597.47 μmol h⁻¹ g⁻¹) and in residual dyestuff degradation (methyl orange, MO; degradation rate constant of 0.1406 min⁻¹). Noteworthily, these two exceptionally high values respectively represent 30.73 and 5.42 times enhancements vs. results obtained with bare g-C₃N₄. Another strong point of our g-C₃N₄/Ag:ZnIn₂S₄ is its impressive recyclability for 20 runs, with no relevant metal release in the aqueous solution following photocatalysis. This work introduces new, superior access to highly efficient photocatalysts founded on 2D/2D nanocomposites serving both the production of hydrogen as an energy carrier and environmental remediation.

By focusing on recent developments on natural and non-natural azasugars (iminocyclitols), this review bolsters the case for the role of olefin metathesis reactions (RCM, CM) as key transformations in the multistep syntheses of pyrrolidine-, piperidine- and azepane-based iminocyclitols, as important therapeutic agents against a range of common diseases and as tools for studying metabolic disorders. Considerable improvements brought about by introduction of one or more metathesis steps are outlined, with emphasis on the exquisite steric control and atom-economical outcome of the overall process. The comparative performance of several established metathesis catalysts is also highlighted.