Pterin, an analog of guanine, is an electron transfer compound in biological systems. Among the analogs, 6-formylpterin (6FP) has been demonstrated to have many marked physiological and pharmacological activities and it is, therefore, worthwhile to elucidate whole mechanism of its activities. Unfortunately, however, 6FP is hardly soluble in water and organic solvents. Like nucleic acid bases, 6FP makes intermolecular hydrogen bonds and forms stacking structure causing such drawback nature. This has made mechanistic studies on 6FP activities extremely difficult. In this study, we carried out derivatization for 6FP and succeeded in increasing water solubility with maintaining its physiological activities.