Following the thio-conjugate addition of (±)-9, its enantiomers were extremely efficiently discriminated using Novozym 435®. The thio-differentiating unit may then be removed either under reductive conditions, using Raney nickel, or following an oxidation–elimination sequence. In this manner enantioenriched derivatives of 1, 1-dioxo-2, 3-dihydro-1H-1λ6- thiophen-3-ol 9 may be accessed.
