Optically Active Carbon: Kinetic Resolution of C76 by Asymmetric Osmylation

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Science  25 Jun 1993:
Vol. 260, Issue 5116, pp. 1918-1920
DOI: 10.1126/science.260.5116.1918


The chiral fullerene C76 was kinetically resolved by asymmetric osmylation providing an example of an optically active allotrope of a pure element. C76 recovered from the treatment of racemic C76 with OsO4 and a chiral alkaloid ligand, showed a specific rotation [α]D of -4000° (> 97 percent enantiomeric excess) and a circular dichroism spectrum corresponding to the ultraviolet spectrum. Regenerated C76 formed by reducing the asymmetrically osmylated C76 with SnCl2 was enriched in the opposite enantiomer. Analysis of the local curvature of the C76 molecule indicated that OsO4 should selectively add to 2 of the 30 types of bonds in C76. This regioselectivity was supported chromatographically and interpreted in terms of the kinetic resolution.