The present invention relates to diastereomers of 10-propargyl-10-deazaaminopterin, compositions comprising optically pure diastereomers of 10-propargyl-10-deazaaminopterin, in particular the two (R,S) diastereomers about the C10 position, specifically, diastereomers (2S)-2-[[4-[(1S)-1-[(2,4-diaminopteridin-6-yl)methyl]but-3-ynyl]benzoyl]amino]pentanedioic acid and/or (2S)-2-[[4-[(1R)-1-[(2,4-diaminopteridin-6-yl)methyl]but-3-ynyl]benzoyl]amino]pentanedioic acid. Methods of preparation of these diastereomers, compositions containing them, and their use for the treatment of conditions related to inflammatory disorders and cancer are also disclosed.
