Asymmetric Autocatalysis Triggered by Carbon Isotope (13C/12C) Chirality
Tsuneomi Kawasaki,
Yukari Matsumura,
Takashi Tsutsumi,
Kenta Suzuki,
Masateru Ito,
Kenso Soai*
Many apparently achiral organic molecules on Earth may be chiral
because of random substitution of the 1.11% naturally abundant
13C for
12C in an enantiotopic moiety within the structure.
However, chirality from this source is experimentally difficult
to discern because of the very small difference between
13C
and
12C. 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.
* To whom correspondence should be addressed. E-mail: soai{at}rs.kagu.tus.ac.jp
