[Show abstract][Hide abstract] ABSTRACT: Mesoporous silica has been used as a heterogeneous support of catalysts; however, asymmetric induction by 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 of asymmetric autocatalysis to afford (S) and (R)-pyrimidyl alkanol with >99.5% ee, respectively.
Chemical Communications 03/2015; 51(42). DOI:10.1039/C5CC01750E · 6.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A chiral mineral, cinnabar, served as a chiral source of asymmetric autocatalysis to afford enantioenriched 5-pyrimidyl alkanol. The adsorption structures of related compounds were observed with atomic force microscopy. Enantioselective adsorption of the asymmetric autocatalyst was found in microcrystal formations at the chiral surface of cinnabar.
[Show abstract][Hide abstract] ABSTRACT: Zeig deine beste Seite: Bei einem achiralen Pyrimidin-5-carbaldehyd, der einen achiralen Kristall () mit enantiotopen (001)- und ()-Seiten bildet, addiert sich iPr2Zn enantioselektiv an die einzelne exponierte enantiotope Oberfläche unter Bildung hoch enantiomerenangereicherter sekundärer S- und R-Alkohole (siehe Schema). Die Absolutkonfiguration des Alkoholprodukts korreliert mit der Ausrichtung des prochiralen Aldehyds im achiralen Kristallgitter.
[Show abstract][Hide abstract] ABSTRACT: Asymmetric autocatalysis initiated by chiral crystals containing racemic DL-serine was achieved. P- and M-crystals of DL-serine acted as the source of chirality of asymmetric autocatalysis to afford highly enantioenriched (>99.5% ee) (S)- and (R)-pyrimidylalkanols after the amplification of ee. This is the first example of the usage of the crystal, which contains the same number of D- and L-enantiomers as an origin of chirality in enantioselective synthesis.
[Show abstract][Hide abstract] ABSTRACT: The enantioselective formation of chiral crystal of achiral nucleobase cytosine was achieved mediated by the crystal direction selective dehydration of crystal water in the achiral crystal of cytosine monohydrate (P2(1)/c). Heat transfer from the enantiotopic face of the single crystal of cytosine monohydrate afforded the enantiomorphous crystal of anhydrous cytosine.
Journal of the American Chemical Society 03/2010; 132(9):2874-5. DOI:10.1021/ja1000938 · 12.11 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: 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.
Journal of Systems Chemistry 01/2010; 1(1):1-6. DOI:10.1186/1759-2208-1-5
[Show abstract][Hide abstract] ABSTRACT: The synthetic hectorite containing intercalated chiral Delta- and Lambda-tris(1,10-phenanthroline)ruthenium(II) ions acts as a heterogeneous chiral catalyst in the enantioselective addition of diisopropylzinc to pyrimidine-5-carbaldehyde to afford, in combination with asymmetric autocatalytic amplification of enantiomeric excess, 5-pyrimidyl alkanol with high enantiomeric excess.
[Show abstract][Hide abstract] ABSTRACT: 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.
[Show abstract][Hide abstract] ABSTRACT: Chiral crystals of achiral benzils act as efficient chiral initiators of asymmetric autocatalysis to afford highly enantioenriched pyrimidyl alkanols whose absolute configurations depend upon the enantiomorph of the crystal used in conjunction with asymmetric autocatalysis with amplification of enantiomeric excess.
[Show abstract][Hide abstract] ABSTRACT: (Chemical Equation Presented) Crystals to add chirality: Cytosine, a prebiotic achiral biomolecule and an essential nucleobase, spontaneously forms enantioenriched crystals if stirring is applied during crystallization. The chiral crystal of achiral cytosine is a chiral initiator for asymmetric autocatalysis of a pyrimidyl alkanol with amplification of the ee value, which provides a nearly enantiopure alcohol with an absolute configuration correlated to that of the cytosine crystal.
[Show abstract][Hide abstract] ABSTRACT: Highly enantioenriched 5-pyrimidyl alkanol was formed using tetrathia--helicenes as a chiral initiator in the enantioselective addition of diisopropylzinc to pyrimidine-5-carbaldehyde, in conjunction with asymmetric autocatalysis.
[Show abstract][Hide abstract] ABSTRACT: 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.
Chemical Communications 06/2006; 37(17):1869-71. DOI:10.1039/b602442d · 6.83 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: An enantiomerically enriched pyrimidyl alkanol with either S or R configurations was obtained stochastically from the reaction between pyrimidine-5-carbaldehyde and diisopropylzinc in the presence of achiral silica gel in conjunction with asymmetric autocatalysis with amplification of chirality.
[Show abstract][Hide abstract] ABSTRACT: 5-Pyrimidyl alkanol with an enantiomeric excess of up to 96% was formed using chiral epoxides as a chiral initiator in the enantioselective addition of diisopropylzinc to pyrimidine-5-carbaldehyde, in conjunction with asymmetric autocatalysis.