Photo-Addition of Amino Acid Methyl Esters to [60]Fullerene

Since their discovery in 1985 and early after the development of a method of efficient synthesis, countless studies showed that fullerenes and derivatives exhibit paramount potentialities in several fields of science and technology.

While some authors consider that the chemistry of fullerenes is now well established, several issues remain to be clarified.^[1] In particular, the synthesis of poly-adducts is difficult to control because it leads to many isomers.

The photo-addition of amino acids to C₆₀ may be a facile route for C₆₀-poly-adduct synthesis. However, the involved mechanism and the maximum number of adducts remained to be ascertained.

Recently, we proposed two possible mechanisms of photo-addition of glycine methyl ester (GME) to C₆₀. The first one involves the concomitant addition of two GME radicals followed by an unprecedented cyclization mechanism leading to fulleropyrrolydines (FP) formation. The second one involves several steps leading to azomethine ylide (AMY), which undergoes a [2+3] cyclo-addition to C₆₀.

To check this assumption, we used HRMS and HPLC-MS to systematically investigate the composition and the evolution of the reaction mixture during irradiation.  Our results show that: 1- AMY is present in the final mixture, which confirm the second mechanism,  and 2- the maximum number of adducts on C₆₀ is equal to 6.^[2]

Similar experiments with other amino acids are currently performed in our laboratory. Preliminary results suggest that this reaction can be generalized to all amino acid classes.

References :

[1]Martin, N, Chem Commun. 2006, 2093—2104.

[2] de Person M, Coffre A, Skanji R, Ben Messaouada M, Abderraba M, Zhang Y, Moussa F Tetrahedron  2013, 69, 6826-31.