No abstract

Mesoporous silica has been used as a heterogeneous support for catalysts; however, asymmetric induction by the helicity of inorganic mesoporous silica itself has not yet been achieved. P- and M-helical mesoporous silica was found to act as a chiral inorganic trigger for asymmetric autocatalysis to afford (S) and (R)-pyrimidyl alkanol with >99.5% ee, respectively.

Enantiomorphous crystals composed of achiral hippuric acid, i.e., naturally occurring N-benzoylglycine, have been used successfully as chiral inducers in enantioselective synthesis in combination with asymmetric autocatalysis to afford the product with extremely high enantiomeric excess.

Cryptochiral isotactic polystyrene induces the enantioselective addition of diisopropylzinc to pyrimidine-5-carbaldehyde, affording the enantioenriched pyrimidyl alkanol with the corresponding absolute configuration to that of polystyrenes in conjunction with asymmetric autocatalysis.

The origin of homochirality of organic compounds such as L-amino acids and D-sugars have intrigued many scientists, and several hypotheses regarding its homochirality have been proposed. According to the statistical theory, small fluctuations in the ratio of the two enantiomers are present in a racemic mixture obtained from the reaction of achiral molecules. We report herein the reaction of pyrimidine-5-carbaldehyde and diisopropylzinc in the presence of achiral amine such as N,N'-dimethylpiperazine, N,N'-diethylpiperazine or N-methylmorpholine but in the absence of a chiral substance. The stochastic formation of (S)-and (R)-pyrimidyl alkanols with detectable ee was observed. This study shows that the slight fluctuation of the enantiomeric ratio of pyrimidyl alkanol produced at the initial reaction step can be enhanced significantly in conjunction with asymmetric autocatalysis with amplification of enantiomeric excess. We believe that the stochastic behavior in the formation of pyrimidyl alkanol constitutes one of the conditions necessary for spontaneous absolute asymmetric synthesis.

Enantioselective syntheses O 0031Enantioselective Synthesis Mediated by Chiral Crystal of Achiral Hippuric Acid in Conjunction with Asymmetric Autocatalysis. -Enantiomorphous crystals obtained from methanol solutions of achiral hippuric acid (N-benzoylglycine) by slow evaporation are used successfully as chiral inducers in enantioselective synthesis. In combination with asymmetric autocatalysis the products are produced with high enantioselectivities. -(KAWASAKI, T.; SUZUKI, K.; HATASE, K.; OTSUKA, M.; KOSHIMA, H.; SOAI*, K.; Chem.