Circulardichroismus von Aminosäuren im Vakuum-Ultravioletten

Four-Component Ugi Reaction for Optical Chirality Sensing and Surface Nanoengineering of Chiral Self-Assemblies

Using green chemistry to control chirality at hierarchical levels as well as chiroptical activities endows with new opportunities to the development of multiple functions. Here, the four-component Ugi reaction is introduced for the general and precise optical chirality sensing of amines as well as the surface nanoengineering of chiral soft self-assemblies. To overcome the relatively weak Cotton effects, direct synthesis of a folded peptide structure on a rotatable ferrocene core with axial chirality was accomplished from chiral amine, 1,1'-ferrocenyl dicarboxylic acid, formaldehyde and isocyanide. Enhanced Cotton effects benefiting from the folded structure allow for the precise and quantitative sensing of natural and synthetic chiral amines covering alkyl, aromatic amines and amino acid derivatives. In addition, aqueous reaction enables the modification of amine-bearing dye to microfibers self-assembled from π-conjugated amino acids. Surface dye-modification via Ugi reaction barely changes the pristine morphology, showing non-invasive properties in contrast to dye staining, which is applicable in soft nano/microarchitectures from self-assembly. This work which combines the four-component Ugi reaction to enable precise ee% detection and surface nanoengineering of soft chiral assemblies sheds light on the advanced application of green chemistry to chirality science.

Chirality, photochemistry and the detection of amino acids in interstellar ice analogues and comets

The primordial appearance of chiral amino acids was an essential component of the asymmetric evolution of life on Earth. In this tutorial review we will explore the original life-generating, symmetry-breaking event and summarise recent thoughts on the origin of enantiomeric excess in the universe. We will then highlight the transfer of asymmetry from chiral photons to racemic amino acids and elucidate current experimental data on the photochemical synthesis of amino and diamino acid structures in simulated interstellar and circumstellar ice environments. The chirality inherent within actual interstellar (cometary) ice environments will be considered in this discussion: in 2014 the Rosetta Lander Philae onboard the Rosetta space probe is planned to detach from the orbiter and soft-land on the surface of the nucleus of comet 67P/Churyumov-Gerasimenko. It is equipped for the in situ enantioselective analysis of chiral prebiotic organic species in cometary ices. The scientific design of this mission will therefore be presented in the context of analysing the formation of amino acid structures within interstellar ice analogues as a means towards furthering understanding of the origin of asymmetric biological molecules.