Absolute asymmetric synthesis autocatalysis

We describe highly enantioselective asymmetric autocatalysis with amplification of chirality and asymmetric autocatalysis initiated by chiral triggers. Asymmetric autocatalysis correlates between the origin of chirality and the homochirality of organic compounds. We also describe spontaneous absolute asymmetric synthesis in combination with asymmetric autocatalysis. 

Spontaneous absolute asymmetric synthesis is described in the formation of enantiomerically enriched pyrimidyl alkanol from the reaction of pyrimidine-5-car-baldehyde and /-Pr2Zn without adding chiral substance in combination with asymmetric autocatalysis. The approximate stochastic distribution of the absolute conhgurations of the product pyrimidyl alkanol strongly suggests that the reaction is a spontaneous absolute asymmetric synthesis. 

E. Stochastic Production of S- and /7-Enantiomers without Adding a Chiral Source by Asymmetric Autocatalysis Spontaneous Absolute Asymmetric Synthesis... 

In the absence of any chiral factors, the probability of the formation of S- and 77-enantiomers is 1 to 1. However, the numbers of the resulting two enantiomers are not exactly the same in almost all cases. Mislow197 described the inevitability of small enantiomeric enrichment in absolute asymmetric synthesis. According to the statistics, it is expected that a fluctuation in the ratio of the S- and 77-enantiomers becomes more and more likely as the numbers in the enantiomer mixture become smaller198. Thus, if the asymmetric autocatalysis is initiated without adding any chiral substance, small fluctuations of enantiomers produced in the initial stage could be enhanced by consecutive asymmetric autocatalytic reaction of pyrimidyl alkanol with amplification of chirality. 

Spontaneous Absolute Asymmetric Synthesis in Conjunction with Asymmetric Autocatalysis... 

Fig. 17 Absolute asymmetric synthesis observed by 1H NMR. The lower trace is a solution of the racemic square planar dimer in toluene-ds with separate signals for (R, S [low field]) and (R, R ) forms. The upper trace shows the final product of autocatalysis without initial added catalyst, giving a product of >80% ee...

One of the main features of asymmetric autocatalysis and the formation of the helix is that the initial extremely low enantioenrichment is amplified significantly to near enantiopure. These processes of amplification of chirality have become powerful tools to elucidate the origin of chirality of organic compounds. For example, by using asymmetric auto catalysis, spontaneous absolute asymmetric synthesis without the intervention of any chiral factor has been realized. 

Singleton, D. A. Vo, L. K. A Few Molecules Can Control the Enantiomeric Outcome. Evidence Supporting Absolute Asymmetric Synthesis Using the Soai Asymmetric Autocatalysis. Org. Lett. 2003,5, 4337. 

Suzuki, K Hatase, K. Nishiyama, D. Kawasaki, T. Soai, K. Spontaneous Absolute Asymmetric Synthesis Promoted by Achiral Amines in Gonjunction with Asymmetric Autocatalysis. /. Syst. Chem. 2010,1, 5. 

Keywords Amplification of ee Asymmetric autocatalysis Automultiplication Chiral discrimination Circularly polarized light Quartz Isotope chirality Origin of chirality Pyrimidyl alkanol Spontaneous absolute asymmetric synthesis... 

Barabas B, Toth J, Palyi G (2010) Stochastic aspects of asymmetric autocatalysis and absolute asymmetric synthesis. J Math Chem 48 457-489. doi 10.1007/sl0910-010-9680-8... 

Barabas B, Caglioti L, Micskei K, Palyi G (2009) Data-based stochastic approach to absolute asymmetric synthesis by autocatalysis. Bull Chem Soc Jpn 82 1372-1376. doi 10.1246/ bcsj.82.1372... 

Meanwhile, we noticed a short review by Wynberg in the same year on asymmetric autocatalysis [22]. He introduced the theoretical paper of Frank [23] on spontaneous asymmetric synthesis. He explained that no experimental realization of asymmetric autocatalysis had ever been achieved. He also described the potential difficulties to realize asymmetric autocatalysis (1) chiral product should have the catalytic activity for producing itself, (2) asymmetric autocatalyst of certain absolute configuration should induce the same absolute configuration of the product, and (3) enantiomeric excess of the product should not decrease because the repeated... 

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