Selective precipitation of alpha-aryl carboxylic acid salts

摘要

A process is provided whereby S(+)-ibuprofen or R(-)-ibuprofen L-lysinate salt is produced by selective precipitation from a mixture containing enantiomers of ibuprofen and L-lysine. The quantity of L-lysine is not more than about a molar equivalent of the quantity of one of the enantiomers in the ibuprofen enantiomeric mixture. Upon precipitation of one ibuprofen enantiomer from the mixture, the overall precipitate and reaction mixture can be held for a sufficient period of time at a second temperature to allow the first precipitate to redissolve into the reaction mixture and the other ibuprofen enantiomer to precipitate out of the mixture in the salt form. Optically active ibuprofen is racemized by being heated at 100 DEG C. to 300 DEG C. in the substantial absence of other materials.