Synthesis of fullerene amino acid derivatives by direct interaction of amino acid ester with C-60

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(CH2N(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.