| abstract |
A process for preparing a crystalline, carbapenem monosodium salt of formula IIa: n n n characterized by the steps a) adding about 10 to 30% of an organic solvent to an aqueous solution of the carbapenem, b) cooling the resulting solution to less than −5° C., c) adjusting the pH using a solution containing an acid in an organic solvent to give the appropriate pH for crystallization, and d) crystallizing the compound by adding methanol, and a C 2-5 alcohol at between −5 and −25° C. |