Polymeric redox-responsive delivery systems bearing ammonium salts cross-linked via disulfides

• Christian Dollendorf,
• Martin Hetzer and
• Helmut Ritter

Beilstein J. Org. Chem. 2013, 9, 1652–1662, doi:10.3762/bjoc.9.189

• successfully synthesized by cross-linking reactions via quaternary ammonium compounds with the disulfide-bearing cross-linker CL 1. The ability of the polymer network to enclose and release substances by reductive cleavage or oxidative formation of disulfide bonds was shown exemplarily using different dyes

• poly(DEAAm-co-DMAEMA) (right) in distilled water. (b) Reductive cleavage of cross-linked poly(DEAAm-co-DMAEMA) networks containing phenolphthalein in pH 10 buffer solution. Storage modulus G’ as function of applied shear stress τ for samples 4 and 5 containing different amounts of CL 1 or CL 2. Storage

• (empty symbols) and 30% H2O2 (half symbols). Swelling degree Q of polymer discs 4–6 as a function of the amount and type of containing cross-linker. (a) Synthesis of a polycationic cross-linked hydrogel containing disulfide groups. (b) Reductive cleavage and oxidative rebuilding of disulfide groups in

Novel synthesis of pseudopeptides bearing a difluoromethyl group by Ugi reaction and desulfanylation

• Jingjing Wu,
• Hui Li and
• Song Cao

Beilstein J. Org. Chem. 2011, 7, 1070–1074, doi:10.3762/bjoc.7.123

• continuation of our interest in the synthesis of diverse difluoromethyl-containing pseudopeptides, we herein report a novel and efficient synthesis of difluoromethyl-containing pseudopeptides through Ugi reaction, with gem-difluoromethylene-containing acid as a key component, followed by reductive cleavage of

• building block 2 were subjected to Ugi reaction under solvent-free conditions, followed by reductive cleavage of the phenylsulfanyl group. It was found that both Ugi reaction and desulfanylation proceeded smoothly for all substrates used to give the corresponding difluoromethylene-containing and

• building block 2,2-difluoro-2-(phenylthio)acetic acid (2) as one component, followed by removal of the phenylsulfanyl protecting group in the presence of tributyltin hydride and azobisisobutyronitrile. Keywords: difluoromethyl functionality; gem-difluoromethylene-containing acid; pseudopeptides; reductive

Photocycloaddition of aromatic and aliphatic aldehydes to isoxazoles: Cycloaddition reactivity and stability studies

• Axel G. Griesbeck,
• Marco Franke,
• Jörg Neudörfl and
• Hidehiro Kotaka

Beilstein J. Org. Chem. 2011, 7, 127–134, doi:10.3762/bjoc.7.18

• . Photochemical ring contraction of isoxazoles 7f–7h. Photocycloaddition of aromatic aldehydes to di- and trimethyl isoxazoles 7d and 7e. Preparative photocycloadditions of 7e with aromatic aldehydes. T-type photochromism of isoxazole–aldehyde pairs. Reductive cleavage of the trimethylisoxazole adduct 9a

Design and synthesis of a cyclitol-derived scaffold with axial pyridyl appendages and its encapsulation of the silver(I) cation

• Pierre-Marc Léo,
• Christophe Morin and
• Christian Philouze

Beilstein J. Org. Chem. 2010, 6, 1022–1024, doi:10.3762/bjoc.6.115

• , upon complexation with participation of three oxygen atoms in the binding, no substantial rearrangement of this semi-rigid structure is to be expected. In addition, reductive cleavage of one of the ortho-ester C–H benzylic bonds, which is known to yield a free hydroxy group [15][16], would allow