IMPROVED PROCESS FOR THE PREPARATION OF STABLE CRYSTALLINE FORM-I OF LINEZOLID, SUBSTANTIALLY FREE OF RESIDUAL SOLVENT

摘要

The invention relates to a substantially pure linezolid hydroxide having R-isomer content more than about 99.9% relative to its S-isomer. Further aspect of invention provides the ambient moisture condition, which is critical for enantiomeric pure linezolid hydroxide. The obtained substantially enantiomerically pure linezolid hydroxide compound of formula-II can be subsequently converted into the linezolid compound of formula-I, having S-isomer content more than 99.9% relative to R-isomer. Further the invention provides an improved process for preparation of enantiomeric pure linezolid Form-I, wherein linezolid Form-I having the purity more than 99.9% relative to any other known polymorphic form of linezolid. The obtained enantiomeric pure linezolid Form-I can be subsequently converted into the other known polymorphic forms linezolid. The invention also provides stable and substantially solvent-free crystal of Form-I of linezolid.