The sulfonic acid functionality is also present in some naturally occurring compounds, for example, in 6-gingesulfonic acid, extracted from ginger (Zingiberis Rhizoma) which is used as an anti-ulcer drug.7 Due to the biological activity of sulfonic acids, several multistep syntheses have been reported. For example, Corey prepared chiral sulfonic acids via a synthetic sequence in which acetophenone reduction was the key enantio-determining step.8 Di Bella and co- ...
