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

Amino acid esters react with C 60 both thermally and photochemically to give different products. Refluxing a mixture of C 60 and glycine ethyl ester afforded C 60 (Me 2 CHNHCHCOOEt) 1, whereas irradiation of the same mixture produced C 60 (EtOOCCHNHCHCOOEt) 2b as the main product. Photochemical reactions between C 60 and sarcosine esters yielded two pyrrolidine derivatives C 60 (CH 2 N(Me)CHCOOR) 3 and C 60 (ROOCCHNHCHCOOR) 2 (R = Me, Et, CH 2 Ph). Compound 2a is also prepared from the photochemical reaction between C 60 and iminodiacetic methyl ester in high yield. These ester derivatives are difficult to hydrolyze in excess mineral acids. The fullerene dicarboxylic acid C 60 (HOOCCHNHCHCOOH) 5 is synthesized from the tert -butyl derivative C 60 ( t BuOOCCHNHCHCOO t Bu) 4 . A possible radical reaction mechanism for the photochemical reactions is proposed which involves an unprecedented C−N bond breakage.