title: Enantioselective synthesis of endohedral metallofullerenes.
abstract: Endohedral metallofullerenes are promising materials in biomedical and material sciences. In particular, they are of interest as agents for magnetic resonance imaging (MRI), photovoltaic devices, and semimetallic components. The synthesis of chiral endofullerenes represents one step further in the potential use of these carbon allotropes; however, this step has not been addressed so far. In this regard, enantiopure endofullerenes are expected to open new avenues in fields in which chirality is a key issue. Here, the synthesis and characterization of the first chiral endohedral metallofullerenes, namely, chiral bis-adducts of La@C(72), are reported. Eight optically active isomers were obtained by enantioselective 1,3-dipolar cycloaddition of a N-metalated azomethine ylide onto a non-isolated-pentagon rule metallofullerene derivative, La@C(72)(C(6)H(3)Cl(2)), catalyzed by a copper chiral complex. The chiral bis-adducts of La@C(72), isolated by nonchiral HPLC, showed optical purities as high as 98% as revealed by the remarkable positive or negative Cotton effects observed in the circular dichroic spectra.
authors.affiliation: Life Science Center of Tsukuba Advanced Research Alliance, University of Tsukuba, Ibaraki 305-8577, Japan.
authors.forename: Koji
authors.initials: K
authors.lastname: Sawai
authors.forename: Yuta
authors.initials: Y
authors.lastname: Takano
authors.forename: Marta
authors.initials: M
authors.lastname: Izquierdo
authors.forename: Salvatore
authors.initials: S
authors.lastname: Filippone
authors.forename: Nazario
authors.initials: N
authors.lastname: Martín
authors.forename: Zdenek
authors.initials: Z
authors.lastname: Slanina
authors.forename: Naomi
authors.initials: N
authors.lastname: Mizorogi
authors.forename: Markus
authors.initials: M
authors.lastname: Waelchli
authors.forename: Takahiro
authors.initials: T
authors.lastname: Tsuchiya
authors.forename: Takeshi
authors.initials: T
authors.lastname: Akasaka
authors.forename: Shigeru
authors.initials: S
authors.lastname: Nagase
mesh_terms: D037741:Fullerenes / Q000737:chemistry*; D008670:Metals / Q000737:chemistry*; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D037741:Fullerenes; D008670:Metals; D009942:Organometallic Compounds