CS-758 was selected as a candidate for clinical trials, but since its water-solubility was insufficient for an injectable formulation, phosphoryl ester prodrugs were designed. In this study, the synthesis and evaluation of these injectable prodrugs are described. Phosphoryl ester 17 h was soluble in water, and was stable in both water and in a solid state. 17 h was converted to CS-758 in human liver microsome and was also converted to CS-758 in rats after intravenous (i.v.) administration with good conversion speed and efficiency. 17 h (i.v.) reduced the viable cell counts in kidneys in a murine hematogenous Candida albicans infection model and in lungs in a murine pulmonary Aspergillus fumigatus infection model, wherein the effects were comparable to or slightly superior to that of CS-758 (per os).