Summary.

It is known that the manifestation of the anticoagulant activity of 4-hydroxycoumarin derivatives is due to the hydroxyl group at C-4 of the coumarin, as well as to four carbon atoms and the carbonyl group at C-3 of the side chain of the molecule. We made modifications of these molecules. The hydroxyl group was acetylated by acetic acid anhydride. The methyl group of the side chain was substituted by phenyl-, 4-chlorophenyl-, 4-methoxyphenyl-, 4-nitrophenyl-, and biphenyl groups. The modification of the carbonyl group at C-3 of the side chain by hydroxylamine hydrochloride resulted in 1’-acetyl-5’-methyl-3’-phenyl-1’,3’-dihydro-4H-spiro-[chromen-3,2’-pyrol]-2,4-dione (substituted spiro compound). The modification of the hydroxyl group at C-4 or the substitution of the methyl group of the side chain by an aromatic nucleus left the side chain open and the compounds had only one asymmetric C-atom.