Synthesis, Chiroptical Properties, and Configurational Assignment of Fulleroproline Derivatives and Peptides

1,3-Dipolar cycloaddition of azomethine ylides to C 60 leads to fulleroproline derivatives, in which a proline ring is fused on a 6,6-ring junction of the fullerene spheroid. This unnatural amino acid can be manipulated under standard coupling conditions to afford fulleroproline-containing peptides. All optically active fulleroproline derivatives and peptides display a characteristic maximum at 428 nm in CD spectra, which is diagnostic for the assignment of the absolute configuration of the C α atom of the proline ring. Calculation of the CD spectra confirm the configurational assignment.