Molekülchiralität in Meteoriten und interstellarem Eis und das Chiralitätsexperiment an Bord der Kometenmission Rosetta der ESA

Gas-Phase Conformational Map of the Amino Acid Isovaline

Four conformers of the non-proteinogenic α-amino acid isovaline, vaporized by laser ablation, are characterized by Fourier-transform microwave techniques in a supersonic expansion. The comparison between the experimental rotational and ¹⁴ N nuclear quadrupole coupling constants and the ab initio calculated ones provides conclusive evidence for the identification of the conformers. The most stable species is stabilized by an N-H⋅⋅⋅O =C intramolecular hydrogen bond and a cis-COOH interaction, whereas the higher-energy conformers exhibit an N⋅⋅⋅H-O intramolecular hydrogen bond and trans-COOH, as in other aliphatic amino acids. The spectroscopic data herein reported can be used for the astrophysical purpose in a possible detection of isovaline in space.

Frozen Chirality of Tertiary Aromatic Amides: Access to Enantioenriched Tertiary α-Amino Acid or Amino Alcohol without Chiral Reagent

One of the fundamental and intriguing aspects of life is the homochirality of the essential molecules. In this field, the absolute asymmetric synthesis of α-amino acids is a major challenge. Herein, we report access, by chemical means, to tertiary α-amino acid derivatives in up to 96 % ee without using any chiral reagent. In our strategy, the dynamic axial chirality of tertiary aromatic amides is frozen in a crystal and is responsible for the stereoselectivity of the subsequent steps. Furthermore, we could control the configuration of the final product by manually sorting and selecting the initial crystals. Based on vibrational circular dichroism studies, we could rationalize the observed stereoselectivity.