Synthesis and conformational analysis of linear homo- and heterooligomers from novel 2-C-branched sugar amino acids (SAAs).

Sugar amino acids (SAAs), as biologically interesting structures bearing both amino and carboxylic acid functional groups represent an important class of multifunctional building blocks. In this study, we develop an easy access to novel SAAs in only three steps starting from nitro compounds in high yields in analytically pure form, easily available by ceric (IV) mediated radical additions. Such novel SAAs have been applied in the assembly of total nine carbopeptoids with the form of linear homo- and heterooligomers for the structural investigations employing circular dichroism (CD) spectroscopy, which suggest that the carbopeptoids emerge a well-extended, left (or right)-handed conformation similar to polyproline II (PPII) helices. NMR studies also clearly demonstrated the presence of ordered secondary structural elements. 2D-ROESY spectra were acquired to identify i+1 NH ↔ i C 1 H, i C 2 H correlations which support the conformational analysis of tetramers by CD spectroscopy. These findings provide interesting information of SAAs and their oligomers as potential scaffolds for discovering new drugs and materials.

Periodical assembly of repetitive RNA sequences synthesized by rolling circle transcription with short DNA staple strands to RNA-DNA hybrid nanowires.

The long single-stranded RNAs produced from Rolling Circle Transcription (RCT) were used as scaffolds to be folded with a few short DNA staples into RNA-DNA hybrid nanowires.

Microwave irradiated click reactions on silicon surfaces via derivertization of covalently grafted poly(PEGMA) brushes.

Two surface chemistry approaches were realized to complete click reactions at covalently grafted polymer brushes of poly(poly(ethylene glycol) monomethacrylate) on a planar silicon surface (Si-g-P(PEGMAOH)). On one hand, the hydroxyls from Si-g-P(PEGMA-OH) brushes can be replaced by chlorines of thionyl chloride and then chlorines can be substituted with azides of sodium azide to achieve azide-terminated (Si-g-P(PEGMA-N(3))) brushes. On the other hand, the terminal acetylene (Si-g-P(PEGMA-CH(2)C[triple bond]CH)) brushes can be prepared easily by reaction between Si-g-P(PEGMA-OH) and propargyl bromide. Model compounds of acetylene-terminated propargylamine, propiolic acid, and 10-undecynoic acid as well as azide-terminal benzyl azide were chosen to investigate the surface click reactions catalyzed with Cu(II)/sodium L-ascorbate by microwave irradiation under very mild conditions at 30°C for 1h. The stepwise modifications were characterized by two surface-sensitive techniques, Multiple Transmission-Reflection Infrared Spectroscopy (MTR-IR) and X-ray Photoelectron Spectroscopy (XPS), and their spectra were analyzed in detail. The triazole ring v(H-C=) stretching at 3139 cm(-1) and the XPS high-resolution scan of N 1s directly confirm the click reactions. By quantifying their infrared spectra before and after click reactions, we conclude that the click reactions on silicon surfaces by microwave irradiation possess high yield and efficiency. Hence, the microwave irradiated click reaction approaches might open convenient avenues to fabricate functional and hybrid organic/silicon devices.