Expedient Synthesis of Bridged Bicyclic Nitrogen Scaffolds via Orthogonal Tandem Catalysis.

Bridged nitrogen bicyclic skeletons have been accessed via unprecedented site- and diastereoselective orthogonal tandem catalysis from readily accessible reactants in a step economic manner. Directed Pd-catalyzed γ-C(sp )-H olefination of aminocyclohexane with gem-dibromoalkenes, followed by a consecutive intramolecular Cu-catalyzed amidation of the 1-bromo-1-alkenylated product delivers the interesting normorphan skeleton. The tandem protocol can be applied on substituted aminocyclohexanes and aminoheterocycles, easily providing access to the corresponding substituted, aza- and oxa-analogues.

Directed C-H Functionalization Reactions with a Picolinamide Directing Group: Ni-Catalyzed Cleavage and Byproduct Recycling.

An efficient strategy for the cleavage of the picolinamide directing group (DG) and recycling of the byproduct generated has been developed. In this protocol, picolinamides were first Boc activated into tertiary -Boc--substituted picolinamides. These were then cleaved via a Ni-catalyzed esterification reaction with EtOH to give valuable -Boc protected amines.

Universal Readers Based on Hydrogen Bonding or π-π Stacking for Identification of DNA Nucleotides in Electron Tunnel Junctions.

A reader molecule, which recognizes all the naturally occurring nucleobases in an electron tunnel junction, is required for sequencing DNA by a recognition tunneling (RT) technique, referred to as a universal reader. In the present study, we have designed a series of heterocyclic carboxamides based on hydrogen bonding and a large-sized pyrene ring based on a π-π stacking interaction as universal reader candidates. Each of these compounds was synthesized to bear a thiolated linker for attachment to metal electrodes and examined for their interactions with naturally occurring DNA nucleosides and nucleotides by H NMR, ESI-MS, computational calculations, and surface plasmon resonance.

Electronic single-molecule identification of carbohydrate isomers by recognition tunnelling.

Carbohydrates are one of the four main building blocks of life, and are categorized as monosaccharides (sugars), oligosaccharides and polysaccharides. Each sugar can exist in two alternative anomers (in which a hydroxy group at C-1 takes different orientations) and each pair of sugars can form different epimers (isomers around the stereocentres connecting the sugars). This leads to a vast combinatorial complexity, intractable to mass spectrometry and requiring large amounts of sample for NMR characterization.

Fixed-gap tunnel junction for reading DNA nucleotides.

Previous measurements of the electronic conductance of DNA nucleotides or amino acids have used tunnel junctions in which the gap is mechanically adjusted, such as scanning tunneling microscopes or mechanically controllable break junctions. Fixed-junction devices have, at best, detected the passage of whole DNA molecules without yielding chemical information. Here, we report on a layered tunnel junction in which the tunnel gap is defined by a dielectric layer, deposited by atomic layer deposition.

Single-molecule spectroscopy of amino acids and peptides by recognition tunnelling.

The human proteome has millions of protein variants due to alternative RNA splicing and post-translational modifications, and variants that are related to diseases are frequently present in minute concentrations. For DNA and RNA, low concentrations can be amplified using the polymerase chain reaction, but there is no such reaction for proteins. Therefore, the development of single-molecule protein sequencing is a critical step in the search for protein biomarkers.