Fullerene Unsymmetrical Bis‐Adducts as Models for Novel Peptidomimetics

Two classes of unsymmetrical, orthogonally protected bis‐fulleropyrrolidine amino acids have been prepared as models for fullerene‐based peptidomimetics with the carbon sphere inserted into the peptide backbone. Two successive [3+2]cycloadditions of azomethine ylides (thermally generated from formaldehyde and the corresponding orthogonally protected glycino‐amines and ‐acids) to C 60 afforded NHFmoc/CO 2 t Bu and NHBoc/CO 2 Me fulleropyrrolidine couples, offering the possibility of selective deprotection under both acidic and basic conditions. In both classes of unsymmetrical bis‐adducts, the distribution of all the trans ( t 1 – t 4 ) and equatorial ( e′ and e″ ) isomers was quite similar except for the t 3 NHBoc/CO 2 Me compound, which rapidly decomposed during chromatography. All compounds were characterized by UV/Vis, 1 H and 13 C NMR spectroscopy, and mass spectrometry.