Synthesis of Fullerene Amino Acid Derivatives by Direct Interaction of Amino Acid Ester with C60

Amino acid esters react with C60 both thermally and photochemically to give different products. Refluxing a mixture of C60 and glycine ethyl ester afforded C60(Me2CHNHCHCOOEt) 1, whereas irradiation of the same mixture produced C60(EtOOCCHNHCHCOOEt) 2b as the main product. Photochemical reactions between C60 and sarcosine esters yielded two pyrrolidine derivatives C60(CH2N(Me)CHCOOR) 3 and C60(ROOCCHNHCHCOOR) 2 (R = Me, Et, CH2Ph). Compound 2a is also prepared from the photochemical reaction between C60 and iminodiacetic methyl ester in high yield. These ester derivatives are difficult to hydrolyze in excess mineral acids. The fullerene dicarboxylic acid C60(HOOCCHNHCHCOOH) 5 is synthesized from the tert-butyl derivative C60(tBuOOCCHNHCHCOOtBu) 4. A possible radical reaction mechanism for the photochemical reactions is proposed which involves an unprecedented C−N bond breakage.