FREMGANGSMAATE FOR FREMSTILLING AV OPTISK RENT S-3-MORFOLINO-4-(3'-TERTBUTYLAMINO-2'-HYDROXYPROPOXY)-1,2,5-THIADIAZOL

The novel dialkanoyl, diaroyl or alkanoyl-aroyl L-tartaric acid-O-monoesters of 3-morpholino-4-(3'-tert-butylamino-2'-hydroxypropoxy)-1,2,5-thiadiazol e correspond to the formula (R = the alkyl or aryl group). They are intermediates in the preparation of S-3-morpholino-4-(3'-tert-butylamino-2'-hydroxypropoxy)-1,2,5-thiadiaz ole, i.e. of S-timolol, which has useful beta -blocking activity, as well as of its acid addition salts. The said L-tartaric acid-O-monoesters are prepared from the corresponding L-tartaric anhydride and R,S-timolol, and their resolution is carried out by crystallising the racemic ester from an alcohol or from a mixture of alcohol and water in a pH range from 7 to 2, resulting in the isolation of the L-tartaric acid-O-monoester of S-timolol in optically pure form, from which ester S-timolol is liberated by acid hydrolysis and can be converted to the desired acid salt.