1-(5'-Hydroxy-2'-nitrophenyl)-2-propen-1-ol (2.0 g) is dissolved in dry DMF (100 ml) and thereto are added sodium iodide (1 equivalent), potassium carbonate and 3-t-butoxycarbonylaminopropyl tosylate (1.5 equivalent). The mixture is stirred at 50° C. for 6 hours, and thereto is added ethyl acetate. The mixture is washed with a saturated sodium chloride solution and dried over sodium sulfate. The residue is purified by silica gel column chromatography to give 1-[5'-(3"-t-butoxycarbonylaminopropyloxy)-2'-nitrophenyl]-2-propen-1-ol (3.53 g) as a pale brown caramel.
