Directed synthesis of the new N,N'-disubstituted 5-spirocyclopenten-3-yl-2,4,6-trioxohexohydropyrimidines by ringcloseng metathesis reactions - N. I. Kobyzhcha; V. M. Holovatiuk; Yu. V. Bezuhlyi; V. I. Kashkovskyi (Ukrainian Chemistry Journal, 2015)