0.8 g of 4-(1-allyloxycarbonylaminocyclopropyl)benzoic acid and 0.585 mL of triethylamine were dissolved in 10 mL of anhydrous DMF and combined with 1.16 g of TBTU, stirred for 15 minutes at RT, then combined with 0.4 g of coumaranone and stirred for a further 10 minutes. While cooling with the ice bath, 0.42 g of NaH was added batchwise as a 60% suspension in white oil, the mixture was stirred for 2 hours at RT and, once the reaction had ended, the mixture was diluted with water to a total volume of approximately 150 mL. The mixture was acidified with 2N acetic acid. The crystals were suction filtered and washed with water. Yield: 1.1 g of solid with a melting point of 125° C.-126° C.
