Synthesis of Benzo[c][2,7]naphthyridinones and Benzo[c][2,6]naphthyridinones via Ruthenium-Catalyzed [2+2+2] Cycloaddition between 1,7-Diynes and Cyanamides.

A convenient method for the ruthenium-catalyzed synthesis of benzo[c]naphthyridinone derivatives is reported. The [2+2+2] cycloaddition from various mono- and disubstituted 1,7-diynes and cyanamides provided benzo[c][2,7]naphthyridinones as major products and benzo[c][2,6]naphthyridinones as minor ones in yields of ≤79% and regioselectivities of ≤99:1. This method is amenable to internal and terminal diynes and a number of cyanamides with diverse functional group tolerance.

Mannose-Coated Fluorescent Lipid Microparticles for Specific Cellular Targeting and Internalization via Glycoreceptor-Induced Phagocytosis.

In this work, we report on the development of mannose-coated fluorescent lipid microparticles to study the role of C-type lectin membrane receptors in phagocytosis. The micrometric droplets of soybean oil-in-water emulsion were functionalized with a tailor-made fluorescent mannolipid. The amphiphilic ligand was built from a mannose unit, a lipid C11 spacer, and a naphthalimide fluorophore. The functionalization of the droplets was monitored by fluorescence microscopy as well as their interaction with concanavalin A, which was used as a model lectin in vitro. The use of a monovalent ligand on the surface of emulsion droplets yielded particles with an affinity approximately 40 times higher than that of free mannose. In cellulo, the coated droplets were shown to be specifically internalized by macrophages in a receptor-dependent phagocytic pathway. The naked droplets, on the other hand, displayed very little internalization because of their low immunogenicity. This work thus brings evidence that C-type lectin membrane receptors may act as phagocytic receptors. The functionalization of the droplets with the tailored amphiphilic fluorescent ligand also provides insights into the development of organic fluorescent particles that may prove useful for developing targeted imaging and delivery tools.

Biomimetic flavin-catalyzed aldehyde oxidation.

The oxidation of alkyl and aryl aldehydes to their corresponding carboxylic acids has been achieved through the action of a biomimetic bridged flavin catalyst. The reaction uses readily available 35% aqueous hydrogen peroxide and is operationally simple. The oxidation is a green and sustainable reaction, obviating chlorinated solvents with minimal byproducts.