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 Mn in CD spectra, which is diagnostic for the assignment of the absolute configuration of the C-alpha atom of the proline ring. Calculation of the CD spectra confirm the configurational assignment.