Synthesis of Naphthalimides through Tandem Pd(II)-Catalyzed C(sp3)-H Oxidation and Diels-Alder Reaction Using a Transient Directing Group Strategy.

Naphthalimides have found extensive applications in materials science and pharmaceuticals. It is still highly desirable to develop efficient methods for the synthesis of naphthalimides with structural diversity. In this work, we developed a new approach for the synthesis of naphthalimides via a tandem reaction of o-methylbenzaldehydes and maleimides. The tandem reaction involves Pd(II)-catalyzed benzylic C(sp3)-H oxidation using an amino acid as the transient directing group and Diels-Alder reaction. The subsequent dehydration forms naphthalimides. The reaction introduces the imide moiety and constructs a benzene ring simultaneously, allowing for easy access to a range of naphthalimides with a variety of substituents.

Versatile functionalization of pectic conjugate: From design to biomedical applications.

Pectin exists extensively in nature and has attracted much attention in biological applications for its unique chemical and physical characteristics. Functionalized pectin, especially pectic conjugates, has given many possibilities for pectin to improve its properties and bioactivity as well as to deliver active molecules. To better exploit this strategy of pectic functionalization, this review presents in detail the structural modifications of pectin, different synthetic methods, and design strategies of pectic conjugates involving both traditional chemical and "green" approaches. Here, the research ideas and applications of pectic prodrugs as well as the development of preparation based on pectic conjugates are reviewed, with emphasis on crosslinking systems of functionalized pectin and nanosystems based on self-assembly techniques. We hope this review will provide comprehensive and valuable information for the functionalization and systematization of the pectic conjugate from synthesis to application.

The impact of the methyl esters of homogalacturonan on cellular uptake dependent hypoglycemic activity in IR-HepG2 cells.

A homogalacturonan (HG) FPLP obtained from Ficus pumila L. was reported to have anti-diabetic activity but how this is influenced by degree of methyl-esterification (DM) of HG is unknown. To comprehensively analyze the role of DM in hypoglycemic activity in insulin-resistant HepG2 cells, HG derivatives (0 < DM < 100) were prepared from FPLP (DM25) by alkali or methanol acidified with acetyl chloride. Interestingly, a quadratic curve relationship revealed that hypoglycemic effect increased and then decreased with DM, and which was the most pronounced with DM54. DM might regulate activity by altering the intracellular drug concentration through cellular uptake. Furthermore, HG-DMn (0 < n < 100) were dependent on macropinocytosis, while HG-DMn (30 < n < 100) were also dependent on caveolae-mediated endocytosis. For HG, higher lipophilicity, smaller particle size, and more endocytosis mechanisms involved were favorable for cellular uptake, thereby increasing the intracellular drug concentration and enhancing the hypoglycemic activity. This work provides ideas for future investigations on structure-activity relationships.

Catalyst-Controlled Diastereoselectivity Switch in the Asymmetric [3 + 2] Annulation of Isatin-Derived MBH Carbonates and 5-Alkenylthiazol-4(5H)-ones.

Exploration of the diastereodivergent synthesis of spirocyclic oxindoles has been challenging. Herein we report asymmetric [3 + 2] annulations of isatin-derived Morita-Baylis-Hillman (MBH) carbonates and 5-alkenylthiazol-4(5H)-ones. Interestingly, two different chiral catalysts, amide-phosphine and 4-dimethylaminopyridine (DMAP)-thiourea, could lead to two kinds of diastereomeric dispiro oxindoles with three contiguous stereogenic centers. The hexafluoroisopropanol (HFIP) additive plays a vital role in accelerating the reaction and tuning the diastereoselectivity. Moreover, both annulation adducts could be further converted to structurally diverse spirooxindoles.

Enantioselective [3+2] annulation of isatin-derived MBH-carbonates and 3-nitroindoles enabled by a bifunctional DMAP-thiourea.

A highly enantioselective [3+2] annulation of isatin-derived Morita-Baylis-Hillman (MBH) carbonates and 3-nitroindoles was enabled by a chiral DMAP-thiourea bifunctional catalyst, affording the corresponding polycyclic spirooxindoles bearing three consecutive stereocenters with good to excellent yields and enantioselectivities. Transformations of the annulation product were subsequently elaborated and the preliminary biological assays demonstrated that these artificial spirooxindoles potentially inhibited pancreatic lipase in a dose-dependent manner.