Method for the purification of mycophenolate mofetil

1. Method for the preparation of mycophenolate mofetil comprising the steps of:

(a) esterification of mycophenolic acid or an amine salt of mycophenolic acid with 2-morpholinoethanol;

(b) contacting the mixture obtained in step (a) with water at a pH-value between 1.0 and 3.0;

(c) separating the aqueous phase from the mixture obtained in step (b);

(d) contacting the aqueous phase obtained in step (c) with a water-immiscible solvent;

(e) separating the non-aqueous phase from the mixture obtained in step (d), characterized in that step (d) is carried out at a pH-value between 3.0 and 5.0.

2. Method according to claim 1 wherein step (a) is carried out in a water-immiscible solvent.

3. Method according to claim 2 wherein step (a) is carried out under azeotropic removal of water.

4. Method according to claim 1 wherein step (d) is carried out at a pH-value between 3.5 and 4.5.

5. A composition comprising mycophenolate mofetil and between 0.002% (w/w) and 0.05% (w/w) of a compound of formula (1):

6. A pharmaceutical composition comprising mycophenolate mofetil and between 0.002% (w/w) and 0.05% (w/w) of a compound of formula (1):

7. A medicament which comprises mycophenolate mofetil and between 0.002% (w/w) and 0.05% (w/w) of a compound of formula (1):