Asymmetric photochemistry III

Homochirality - 9 July 2008

One possible explanation for the phenomenon of homochirality is that chiral molecules were brought to prebiotic Earth via meterorites such as the Murchison meteorite. These chiral molecules could very well have been formed via a photodecomposition process en route to Earth with CPL originating from synchrotron radiation from a neutron star although it must be stressed that even then there is no preference for handedness.

In 1977 Bonner et al ( DOI) prepared optically active leucine (a biologically relevant compound) in around 2% enantiomeric excess from asymmetric photodecomposition of racemic leucine.

In 1996 Inoue et al. ( DOI) demonstrated photoderacemization in cyclooctene. The trans isomer can be resolved as a pair of enantiomers with very high optical rotation.

It is found that the (R)-form is isomerized to achiral cis-cyclooctene by l-CPL leaving the (S)-form in solution and vice versa. In this experiment synchrotron UV light was used to mimic interstellar conditions.