Asymmetric autocatalysis triggered by carbon isotope ([sup.13]C/[sup.12]C) chirality

Many apparently achiral organic molecules on Earth may be chiral because of random substitution of the 1.11% naturally abundant [sup.13]C for [sup.12]c in an enantiotopic moiety within the structure. However, chirality from this source is experimentally difficult to discern because of the very small difference between [sup.13]C and [sup.12]C. We have demonstrated that this small difference can be amplified to an easily seen experimental outcome using asymmetric autocatalysis. In the reaction between pyrimidine-5-carbaldehyde and diisopropylzinc, addition of chiral molecules in large enantiomeric excess that are, however, chiral only by virtue of isotope substitution causes a slight enantiomeric excess in the zinc alkoxide of the produced pyrimidyl, alkanol. Asymmetric autocatalysis then leads to pyrimidyl alcohol with a large enantiomeric excess. The sense of enantiomeric excess of the product alcohol varies consistently with the sense of the excess enantiomer of the carbon isotopically chiral compound.