Spatially resolved acyl transfer on surface by organo-catalytic scanning probe nanolithography (o-cSPL).

Groundbreaking research done in the area of nanolithography makes it a versatile tool to produce nanopatterns for a broad range of chemical surface functionalization or physical modifications. We report for the first time an organocatalytic scanning probe nanolithography (o-cSPL) approach. Covalent binding of an organocatalyst on the apex of an atomic force microscope (AFM) tip gives way to a system that allows the formation of locally defined acylated-alcohol patterns on self-assembled monolayers (SAMs).

Signal transduction in oligoamide foldamers by selective non-covalent binding of chiral phosphates at a urea binding site.

The transduction of biological signals depends on the spatial communication of conformational change. We report a synthetic mimic of this signal transduction process in which non-covalent binding induces a change in the position of equilibrium between two rapidly interconverting screw-sense conformers of a synthetic helical polyamide. Selectivity was achieved by incorporating at the N-terminus of the polyamide a urea-based anion recognition site capable of binding chiral phosphate anions.

Design of chiral urea-quaternary ammonium salt hybrid catalysts for asymmetric reactions of glycine Schiff bases.

Bifunctional chiral urea-containing quaternary ammonium salts can be straightforwardly synthesised in good yield and with high structural diversity a scalable and operationally simple highly telescoped sequence starting from -1,2-cyclohexanediamine. These novel hybrid catalysts were systematically investigated for their potential to control glycine Schiff bases in asymmetric addition reactions. It was found that Michael addition reactions and the herein presented aldol-initiated cascade reaction can be carried out to provide enantiomeric ratios up to 95 : 5 and good yields under mild conditions at room temperature.

Towards Tartaric-Acid-Derived Asymmetric Organocatalysts.

Tartaric acid is one of the most prominent naturally occurring chiral compounds. Whereas its application in the production of chiral ligands for metal-catalysed reactions has been exhaustively investigated, its potential to provide new organocatalysts has been less extensively explored. Nevertheless, some impressive results, such as the use of TADDOLs as chiral H-bonding catalysts or of tartrate-derived asymmetric quaternary ammonium salt catalysts, have been reported over the last decade.

Application scope and limitations of TADDOL-derived chiral ammonium salt phase-transfer catalysts.

We have recently introduced a new class of chiral ammonium salt catalysts derived from easily available TADDOLs. To get a full picture of the scope of application and limitations of our catalysts we tested them in a variety of different important transformations. We found that, although these compounds have recently shown their good potential in the asymmetric α-alkylation of glycine Schiff bases, they clearly failed when we attempted to control more reactive nucleophiles like b-keto esters.

Investigations Concerning the Syntheses of TADDOL-Derived Secondary Amines and Their Use To Access Novel Chiral Organocatalysts.

A structurally carefully diversified library of novel TADDOL-derived chiral secondary amines was synthesized and investigated for their applicability to obtain new organocatalysts like chiral Lewis bases and chiral phase-transfer catalysts. The scope and limitations of the developed syntheses routes to access these catalysts as well their catalytic performance in different benchmark reactions were systematically investigated. The most powerful of the catalysts prepared was found to be highly useful for the phase-transfer catalyzed α-alkylation of glycine Schiff base (high yields and up to 93% ee).

Design, synthesis, and application of tartaric acid derived N-spiro quaternary ammonium salts as chiral phase-transfer catalysts.

A novel class of tartaric acid-derived N-spiro quaternary ammonium salts was synthesised starting from known TADDOLs. These compounds were found to catalyse the asymmetric α-alkylation of glycine Schiff bases with high enantioselectivities and in good yields.