Kawasaki Tsuneomi, Matsumura Yukari, Tsutsumi Takashi, Suzuki Kenta, Ito Masateru, Soai Kenso
Department of Applied Chemistry, Tokyo University of Science, Kagurazaka, Shinjuku-ku, Tokyo 162-8601, Japan.
Science. 2009 Apr 24;324(5926):492-5. doi: 10.1126/science.1170322. Epub 2009 Mar 26.
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.
地球上许多看似非手性的有机分子可能是手性的，这是因为结构中对映异位部分内1.11%天然丰度的13C随机取代了12C。然而，由于13C和12C之间的差异非常小，实验上很难辨别这种来源的手性。我们已经证明，利用不对称自催化，这种微小的差异可以放大到易于观察的实验结果。在嘧啶-5-甲醛与二异丙基锌的反应中，加入大量对映体过量的手性分子（然而，这些分子仅通过同位素取代才具有手性）会使生成的嘧啶基烷醇的醇锌产生轻微的对映体过量。然后，不对称自催化导致嘧啶醇具有很大的对映体过量。产物醇的对映体过量方向与碳同位素手性化合物对映体过量的方向一致变化。
