Asymmetric Autocatalysis Triggered by Chiral Crystals Formed from Achiral Compounds and Chiral Isotopomers

Asymmetric autocatalysis with amplification of enantiomeric excess is found in the enantioselective addition of diisopropylzinc to pyrimidine-5-carbaldehyde using pyrimidyl alkanol as an asymmetric autocatalyst. Asymmetric autocatalysis has been employed as a method for clarifying the origin of homochirality. Circularly polarized light, inorganic chiral crystals and statistical fluctuation of enantiomeric imbalance act as chiral initiators in asymmetric autocatalysis to afford highly enantioenriched products. We have investigated asymmetric autocatalysis using chiral crystals formed from achiral and racemic compounds as an origin of chirality. Absolute control of the crystal chirality of cytosine was achieved by the removal of crystal water. Enantioselective carbon-carbon bond formation at the enantiotopic crystal face of aldehydes was established using diisopropylzinc vapor. In addition, asymmetric autocatalysis triggered by chiral compounds arising from H, C and O isotope substitution has been achieved.     

Enantioselective automultiplication of chiral molecules by asymmetric autocatalysis

Asymmetric autocatalysis is a process of automultiplication of a chiral compound in which chiral product acts as a chiral catalyst for its own production. The discovery and the development of asymmetric autocatalysis of pyrimidyl-, quinolyl-, and pyridylalkanols are described in the enantioselective additions of diisopropylzinc to the corresponding nitrogen-containing aldehydes. (Alkynylpyrimidyl)alkanols automultiply with a yield of over 99% and over 99.5% ee. Asymmetric autocatalysts with extremely low ee's automultiply with significant amplification of ee's without the need for any other chiral auxiliaries. Small enantiomeric imbalances of chiral molecules induced by physical factors can be amplified by the present asymmetric autocatalysis.     

Anisotropical C2−O reflection bands measured in α-helixes of silk fibroin

From analysis of 36 anisotropical reflectrion spectra of the C₂?O bending bands of silk fibroin at ≈700～200 cm^?1 region at static state, presence of the A, B, C and D-band and reflection edge was also confirmed. Furthermore, we confirmed stepnized reflectivity overlapping on the C₂?O bending bands and stenized values of the reflection integral (optical activity). Second, analysing four diffusion diagrams of these bands, we inspected stepnized polar distribution of the band and quantized polar distribution was confirmed as, θ^N = 27.5·N + 2.5 (degrees) with N=1, 2, 3, 4...12 and 13, without N=5,6 and 7 at θ=120°～180° as in case of polar distribution of the C₂?O and Si?O stretching reflection bands and C₂?O bending band measured in case of silicate cellulose present in the surface skin layer of bamboo's stem.