Patent ID: 7718800

Claim:
A process for preparation of linezolid form III, which is characterized by an x-ray powder diffraction spectrum having peaks expressed as 2θ at about 7.6, 9.6, 13.6, 14.9, 18.2, 18.9, 21.2, 22.3, 25.6, 26.9, 27.9 and 29.9 degrees, and an IR spectrum having main bands at about 3338, 1741, 1662, 1544, 1517, 1471, 1452, 1425, 1400, 1381, 1334, 1273, 1255, 1228, 1213, 1197, 1176, 1116, 1082, 1051, 937, 923, 904, 869, 825 and 756 cm −1 , which comprises the steps of: (a) mixing linezolid with a solvent or a mixture of solvents; (b) cooling the contents to below about 15° C.; (c) optionally seeding the contents with linezolid form III; (d) stirring the contents for at least about 15 minutes; and (e) collecting linezolid form III crystals by filtration or centrifugation; wherein the solvent used in step (a) is selected from the group consisting of ethyl acetate, butyl acetate, and isopropyl alcohol.