Patent ID: 7683188

Claim:
A process for preparing an ester of mycophenolic acid, said process comprising the steps of: a) providing a concentrated aqueous alkaline mixture containing mycophenolic acid; b) admixing the mixture with a first water-immiscible solvent to form an aqueous phase and a first water-immiscible phase; c) separating the aqueous phase; d) admixing the aqueous phase with a second water-immiscible solvent at a pH of less than about 7 to form an aqueous phase and a second water-immiscible phase; e) separating the second water-immiscible phase; f) concentrating the second water-immiscible phase; g) crystallizing mycophenolic acid; and h) converting the mycophenolic acid of step (g) to an ester; wherein said ester is a morpholinoethyl ester or a C 1 -C 4 alkyl ester.