The d,l-phenylpropanolamine (norephedrine) racemate is split with optically active thiazolidine-4-carboxylic acids of the formula:
(https://www.thevespiary.org/rhodium/Rhodium/hive/hiveboard/picproxie_docs/000472855-file_ehxc.jpg) where R1 and R2 are both methyl or are joined together to form the pentamethylene group.
Patent US3959302 (http://l2.espacenet.com/dips/viewer?PN=US3959302&CY=gb&LG=en&DB=EPD)