Chemistry of bicyclic ureas. 5. Synthesis of 2,4,6,8-tetraazabicyclo[3.3.0]-3-octanone-7-thiones

A convenient method was developed for the synthesis of 2,4,6,8-tetraazabicyclo[3.3.0]-3-octanone-7-thiones by reacting the 4,5-dihydroxy- and 4,5-dimethoxy-2-imidazolidinethiones with substituted ureas.