Based on their high photosensitivity, the potential medical application of fullerenes (C₆₀ and C₇₀) such as photodynamic therapy agents has been discussed for decades. Due to their high hydrophobicity, it is necessary to find a good method to solubilize fullerenes in water or water-miscible solvents for such application.  We have been using a biocompatible and water-soluble polymer, poly(vinylpyrrolidone) (PVP) to prepare water-soluble C₆₀/ or C₇₀/PVP complex¹ and C₆₀- or C₇₀-PVP conjugates^{2. 3} with efficient reactive oxygen species (ROSs) generation under visible light.^4,5 However, in the clinical use, well-defined compounds with narrower molecular weight distribution are favored.

In this study, we synthesized a RAFT reagent 1 for the preparation of well-defined PVP. The terminal moiety was converted to an amine 2 to connect to a C₆₀ acid anhydride derivative 3 which was obtained through a Prato reaction.⁶ Obtained C60-PVP conjugate had a narrower molecular distribution, high water-solubility and photoinduced ROS generation.⁷

(1) Yamakoshi, Y.; Yagami, T.; Fukuhara, K.; Sueyoshi, S.; Miyata, N. J. Chem. Soc., Chem. Commun. 1994, 517. (2) Iwamoto, Y.; Yamakoshi, Y. Chem. Commun. 2006, 4805. (3) Oriana, S.; Aroua, S.; Söllner, J. O. B.; Ma, X.; Iwamoto, Y.; Yamakoshi, Y. Chem. Comm. 2013, 49, 9302. (4) Yamakoshi, Y.; Sueyoshi, S.; Fukuhara, K.; Miyata, N. J. Am. Chem. Soc. 1998, 120, 12367. (5) Yamakoshi, Y.; Umezawa, N.; Ryu, A.; Arakane, K.; Miyata, N.; Goda, Y.; Masumizu, T.; Nagano, T. J. Am. Chem. Soc. 2003, 125, 12803. (6) Aroua, S.; Schweizer, W. B.; Yamakoshi, Y. Org. Lett. 2014, 16, 1688. (7) Aroua, S.; Tiu, E. G. V.; Ayer, M.; Ishikawa, T.; Yamakoshi, Y. Polymer Chem. 2015, 6, 2616.