Procedure for crystallization of (22E)-(24R)-2-methylene-22-dehydro-1α,24-25-trihydroxy-19-nor-vitamin D3

A method of purifying (22E)-(24R)-2-methylene-22-dehydro-1α,24,25-trihydroxy-19-nor-vitamin D3, comprising the steps of:

• (a) dissolving (22E)-(24R)-2-methylene-22-dehydro-1α,24,25-trihydroxy-19-nor-vitamin D3 in a volume of ethyl acetate as solvent to prepare a solution of (22E)-(24R)-2-methylene-22-dehydro-1α,24,25-trihydroxy-19-nor-vitamin D3,
• (b) adding a volume of hexane dropwise to the solution, to reach a saturation point, to form a solution of (22E)-(24R)-2-methylene-22-dehydro -1α,24,25-trihydroxy-19-nor-vitamin D3 in a mixture of ethyl acetate and hexane as solvent wherein crystals of (22E)-(24R)-2-methylene-22-dehydro-1α,24,25-trihydroxy-19-nor-vitamin D3 form and precipitate from the solution;
• and
• (c) separating the (22E)-(24R)-2-methylene-22-dehydro-1α,24,25-trihydroxy-19-nor-vitamin D3 crystals from the solution, wherein the (22E)-(24R)-2-methylene-22-dehydro-1α,24,25-trihydroxy-19-nor-vitamin D3 crystals have a crystalline form that has molecular packing arrangement defined by space group P21 and unit cell dimensions:
• a=16.3058(9) Å;
• b=10.0461(6) Å;
• c=26.0527(15) Å;
• α=90°;
• β=109.001(3)°;
• and γ=90°.