Optically active compounds are increasingly important in organic chemistry and in industry. Approximately half of the thousands of drugs known have chiral structures, many of which show dramatic differences in the properties of the stereoisomers (enantiomers) and thus an increasing proportion are marketed as single enantiomers. In the agrochemical field, many marketed compounds have been "switched” from a racemic to single enantiomer form for environmental reasons, since the inactive isomer contributes to pollution. In the flavour and fragrances industry and in molecular electronics, chirality is a key issue in R&D and manufacture.