Crystallization of (20R) 19-nor-24-difluoro-1α,25-dihydroxyvitamin D

1. A compound having the formula

in crystalline form, and named (20R)-19-nor-24-difluoro-1α,25-dihydroxyvitamin D 3 ,

wherein the crystalline form has a molecular packing arrangement defined by space group C2 and unit cell dimensions a=23.88 Å, b=6.16 Å, c=19.63 Å, α=90°, β=121.83° and γ=90°.

2. A three dimensional structure for (20R)-9-nor-24-diafluoro-1α,25-dihydroxyvitamin D as defined by the molecular packing arrangement set forth in claim 1 .

3. A method of purifying (20R)-19-nor-24-difluoro-1α,25-dihydroxyvitamin D 3 , comprising the steps of:

(a) preparing a solvent comprising hexane;

(b) adding a product containing (20R)-9-nor-24-difluoro-1α,25-dihydroxyvitamin D 3 to be purified to said hexane to form a suspension of the product in the hexane;

(c) adding 2-propanol dropwise to the suspension to form a mixture of the product in the hexane and 2-propanol;

(d) heating the mixture to dissolve the product containing (20R)-19-nor-24-difluoro-1α,25-dihydroxyvitamin D- to be purified in said mixture;

(e) cooling said mixture and dissolved product below ambient temperature for a sufficient amount of time to form a precipitate of (20R)-19-nor-24-difluoro-1α,25-dihydroxyvitamin D crystals; and

(f) separating the (20R)-19-nor-24-difluoro-1α,25-dihydroxyvitamin D 3 crystals from the solvent.

4. The method of claim 3 including the further step of allowing said solvent and dissolved product to cool to ambient temperature prior to cooling below ambient temperature.

5. The method of claim 3 wherein the step of separating comprises filtering the mixture and precipitate to obtain the crystals.

6. The method of claim 3 including, a further step (g) comprising repeating steps (a) through (f) using the recovered crystals from step (f) as the product of step (b).

7. The method of claim 3 wherein said mixture comprises about 15% 2-propanol and about 85% hexane by volume.