An improved process of separation of R- and S-timolol

Diastereomeric timolol tartrates 4 are obtained in a one-pot synthesis from the racemic base 2 and optically active O,O-diacetyl- or O,O-dibenzoyltartaric anhydrides 3, as only one of the diastereomers precipitates from acetone solution. Acidic hydrolysis as the corresponding 4 leads to timolol in high yield and optical purity.