First enantiomerically pure C70-adducts with a non-inherently chiral addition pattern

By addn. of an enantiomerically pure nitrile oxide to C70, four chiral isoxazolo[70]fullerene isomers were prepd. and isolated in pure state: two constitutional isomers resulting from addn. to one of the bonds radiating from the polar pentagons, and a constitutionally different pair of diastereoisomers resulting from addn. to a hexagon-hexagon fusion site parallel to the equator of the fullerene. After elimination of the stereogenic center from the side chain, the former two adducts become achiral, while the latter two are sep. transformed into enantiomeric fullerene derivs. with a non-inherently chiral addn. pattern as sole stereogenic element. In the present work, chiral [70]fullerene derivs. with a non-inherently chiral functionalization pattern were isolated in enantiomerically pure form for the first time. Their abs. configuration was assigned based on the good agreement between exptl. CD data and CD spectra calcd. using the ZINDO method.