Tighter Confinement Increases Selectivity of d ‐Glucose Isomerization Toward l ‐Sorbose in Titanium Zeolites

Rare sugar L-sorbose exerts antitumor activity by impairing glucose metabolism

Rare sugars are monosaccharides with low natural abundance. They are structural isomers of dietary sugars, but hardly be metabolized. Here, we report that rare sugar L-sorbose induces apoptosis in various cancer cells. As a C-3 epimer of D-fructose, L-sorbose is internalized via the transporter GLUT5 and phosphorylated by ketohexokinase (KHK) to produce L-sorbose-1-phosphate (S-1-P). Cellular S-1-P inactivates the glycolytic enzyme hexokinase resulting in attenuated glycolysis. Consequently, mitochondrial function is impaired and reactive oxygen species are produced. Moreover, L-sorbose downregulates the transcription of KHK-A, a splicing variant of KHK. Since KHK-A is a positive inducer of antioxidation genes, the antioxidant defense mechanism in cancer cells can be attenuated by L-sorbose-treatment. Thus, L-sorbose performs multiple anticancer activities to induce cell apoptosis. In mouse xenograft models, L-sorbose enhances the effect of tumor chemotherapy in combination with other anticancer drugs. These results demonstrate L-sorbose as an attractive therapeutic reagent for cancer treatment.

Metal Sites in Zeolites: Synthesis, Characterization, and Catalysis

Zeolites with ordered microporous systems, distinct framework topologies, good spatial nanoconfinement effects, and superior (hydro)thermal stability are an ideal scaffold for planting diverse active metal species, including single sites, clusters, and nanoparticles in the framework and framework-associated sites and extra-framework positions, thus affording the metal-in-zeolite catalysts outstanding activity, unique shape selectivity, and enhanced stability and recyclability in the processes of Brønsted acid-, Lewis acid-, and extra-framework metal-catalyzed reactions. Especially, thanks to the advances in zeolite synthesis and characterization techniques in recent years, zeolite-confined extra-framework metal catalysts (denoted as metal@zeolite composites) have experienced rapid development in heterogeneous catalysis, owing to the combination of the merits of both active metal sites and zeolite intrinsic properties. In this review, we will present the recent developments of synthesis strategies for incorporating and tailoring of active metal sites in zeolites and advanced characterization techniques for identification of the location, distribution, and coordination environment of metal species in zeolites. Furthermore, the catalytic applications of metal-in-zeolite catalysts are demonstrated, with an emphasis on the metal@zeolite composites in hydrogenation, dehydrogenation, and oxidation reactions. Finally, we point out the current challenges and future perspectives on precise synthesis, atomic level identification, and practical application of the metal-in-zeolite catalyst system.

Magnesium-mediated Wittig reagent-promoted Stereoselective synthesis of L-Sorbopyranoses from D-Glucopyranoses

l-Sorbose is an important rare sugar that exists in some natural products and widely used in pharmaceutical and chemical industries. Herein, two simple and practical routes were developed using cheap magnesium (II) for the synthesis of 1,3,4,5-tetra-O-benzyl-l-sorbopyranose from 2,3,4,6-tetra-O-benzyl-d-glucopyranose with high stereoselectivity and yield. The first route involved the intramolecular hydride shift from C5 to the C1 of the glucopyranose precursor. Wittig reagent (PPh₃CHCOOBn) was used to combined with Mg(II) to promote this isomerization reaction from d-glucopyranose to l-sorbopyranose in the alternative route.