Enantioselective synthesis of 8-azabicyclo[3.2.1]octanes via asymmetric 1,3-dipolar cycloadditions of cyclic azomethine ylides using a dual catalytic system.

The first example of asymmetric 1,3-dipolar cycloadditions between diazo imine-derived cyclic azomethine ylides and acryloylpyrazolidinone using a rhodium(ii) complex/chiral Lewis acid binary system is reported. The asymmetric cycloadditions afforded optically active 8-oxabicyclo[3.2.

Time-programmed release of fluoroscein isocyanate dextran from micro-pattern-designed polymer scrolls.

In this article we present a relevant strategy for a non-trivial time-programmed release of water-soluble macromolecules from biocompatible μ-containers. The system is based on self-scrolled chitosan acetate (CA) fibers, encapsulated in a poly(dimethylsiloxane) matrix. Mass transfer between a fiber and the external environment takes place via the only opened extremity of the fiber.

Self-scrolling ability of differentially acetylated chitosan film.

Chitosan film cast on a glass slide was exposed to acetic anhydride vapor, resulting in an acetylation gradient in the film, with preferential acetylation of the exposed surface. The difference in degree of acetylation between the two surfaces of the peeled film was confirmed by attenuated total reflection infrared spectroscopy. Upon immersion of the film in water, differential swelling occurred because the more highly acetylated surface absorbed less water, and the resulting bending moment caused self-scrolling with the more highly acetylated surface inside.