Bucky-Bowl-Derived Unnatural Amino Acids and Peptides: Synthesis and Substituent Effect on Bowl Inversion Dynamics and Electronic Structure

Abstract

A new kind of bucky-bowl-derived unnatural amino acids and their peptides have been designed and synthesized. The substituent effect on bowl inversion dynamics and the electronic structure of corannulene-derived amino acids has been examined. The data of the inversion barrier revealed that all amino acid-linked corannulene cognates exhibit a slightly lower inversion barrier in comparison with the pristine corannulene; perhaps due to the repulsion energy between the peri-hydrogen of the corannulene moiety with the amino acid linker, it flattens the bowl and hence lowers the inversion barrier. The temperature of coalescence (T_C) and free energy barrier of unsubstituted corannulene and their corresponding amino acid derivatives were significantly different from the parent corannulene. Electrochemical measurement indicated that amino acid-based bucky-bowl than that of unsubstituted bucky-bowl confirmed the electron-rich character of the group, which is incorporated in the bowl skeleton.