Patent ID: 8049035

Claim:
A method for preparing a crystalline potassium salt of 2-((2S,3R,4E,6E,10E,12S)-13-(4-fluorophenoxy)-2,3,12-trihydroxytridec a-4,6,10-trien-8-ynyloxy)acetate: which is in the form of a monohydrate characterized by a X-ray powder diffraction pattern having a characteristic peak at about d=26.5 Å; in the form of a monohydrate characterized by a X-ray powder diffraction pattern having a characteristic peak at about d=26.5 Å, about d=4.3 Å and about d=4.0 Å; in the form of a dihydrate characterized by a X-ray powder diffraction pattern having a characteristic peak at about d=27.1 Å; or in the form of a dihydrate characterized by a X-ray powder diffraction pattern having a characteristic peak at about d=27.1 Å, about d=4.2 Å and about d=4.1 Å, comprising 1) mixing together a potassium base present in ethanol and/or water, with the free acid corresponding to the salt of Formula (I) present in ethanol and/or water; wherein the resultant suspension contains water; 2) optionally cooling the resulting suspension; 3) isolating the resulting crystals from the resulting suspension; 4) optionally washing the isolated crystals with an ethanol/water mixture; and 5) drying the isolated crystals, to give the crystalline potassium salt (I); or which is in the form of an anhydrate characterized by a X-ray powder diffraction pattern having a characteristic peak at about d=26.7 Å; or in the form of an anhydrate characterized by a X-ray powder diffraction pattern having a characteristic peak at about d=26.7 Å and about d=3.7 Å; comprising 1) digesting a hydrate or a mixture of hydrates of a potassium salt of Formula (I) in 1,4-dioxane; 2) optionally heating the resulting suspension; 3) isolating the resulting crystals; 4) optionally washing the isolated crystals with 1,4-dioxane; and 5) drying the isolated crystals, to give the crystalline anhydrate form of the potassium salt (I).