The present invention relates to diastereomers of 10-propargyl-10-deazaminopterin, compositions comprising optically pure diastereomers of 10-propargyl-10-deazaminopterin, in particular the two (R,S) diastereomers about the C10 position. 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.