By condensation of ethyl 8-propyl-7-hydroxy-4-oxo-4H-1-benzopyran-2-carboxylate (I) with 4-(2,3-epoxypropoxy)-3-propyl-2-hydroxyacetophenone (II) by means of benzyltrimethylammonium hydroxide in refluxing DMF, followed by hydrolysis with NaHCO3 in refluxing ethanol - water. The starting compounds (I) and (II) are prepared as follows: 1) The condensation of 3-propyl-2,4-dihydroxyacetophenone (III) with diethyl oxalate (IV) by means of sodium ethoxide in refluxing ethanol gives (I). 2) The condensation of acetophenone (III) with 1-chloro-2,3-epoxypropane (V) by means of KOH in refluxing ethanol - water gives (II).