Process for the crystallization of a reverse transcriptase inhibitor using an anti-solvent

摘要

A method for crystallizing (-)-6-chloro-4-cyclopropylethynyl-4-trifluoromethyl-1,4-dihydro-2H-3,1 -benzoxazin-2-one from a solvent and anti-solvent solvent system and producing the crystalline product. The desired final crystal form, Form I, can be produced by using a solvent to effect the dissolution of the compound followed by the addition of an anti-solvent to initiate the crystallisation.