Chemical Synthesis-Scale-Up Procedure 5-FU (260 mg, 2.88 mmol) was dissolved in dry NMP (20 mL) and a teflon-coated stir bar was added to a round bottom flask. Hexyl isocyanate (0.437 mL, 0.302 mmol) was added, and the reaction vessel was well-sealed with a glass septum. The reaction was stirred in a heated water bath at 60°C and monitored by thin-layer chromatography (40:60 ethyl acetate in hexanes) for 120 minutes. Upon completion, the reaction was quenched with the addition of 1.0 M aqueous HCl, followed by the addition of ethyl acetate (100 mL) and brine (100 mL). The layers were separated, and the organic layer was washed with saturated brine to remove excess NMP, then dried with MgSO 4 , filtered, and concentrated in vacuo. The crude product was purified via silica gel flash chromatography on a gradient of 100% hexane to 40% ethyl acetate in hexanes to afford carmofur as a white powder (132.3 mg, 50.9% yield). Structural confirmation of the product was confirmed through 1 H and F NMR in d6-DMSO and was identified to be spectroscopically identical to an authentic standard of carmofur.