Asymmetric Autocatalysis with Amplification of Chirality

Abstract

We found that chiral 5-pyrimidyl alkanols are highly enantioselective asymmetric autocatalysts forthe addition of i-Pr2Zn to the corresponding aldehyde.Asymmetric autocatalysis with amplification of ee from extremely low (0.00005%) ee to >99.5% ee wasrealized for the first time by consecutive asymmetric autocatalysis. The chirality of CPL was directlycorrelated with the chirality of the pyrimidyl alkanol with high ee by asymmetric photodegradation of theracemic pyrimidyl alkanol in combination with asymmetric autocatalysis. Chiral inorganic crystals suchas quartz act as chiral triggers and regulate the sense of the asymmetric autocatalysis. Chiral organiccrystals composed of an achiral compound such as hippuric acid act as the initial source of chirality forasymmetric autocatalysis to produce the nearly enantiomerically pure product. Highly sensitive chiral discriminationof amino acids with low ee is described. Direct examination of extraterrestrial chirality was performedon meteorites by applying asymmetric autocatalysis as the chiral sensor. Spontaneous absolute asymmetricsynthesis is described in the formation of enantiomerically enriched pyrimidyl alkanol from the reactionof pyrimidine-5-carbaldehyde and i-Pr2Zn withoutadding any chiral substance in combination with asymmetric autocatalysis. Asymmetric autocatalysis of a chiralpyrimidyl alkanol is the only possible method to discriminate a cryptochiral quaternary saturated hydrocarbon,whose chirality is not capable of determination by any current method. The discrimination of chiralitydue to deuterium substitution is also accessible by the highly sensitive asymmetric autocatalysis.