Abstract With a continuing interest on heteropolycyclic structures which may show biological activities, we synthesized new tricyclic derivatives in which the pyridopyrazine skeleton is fused with pyrazine 7 and 8, B, n= 1. However, the initial design of obtaining also the cyclohomologous structure B (n= 2) produced instead a pyranopyridopyrazine derivative 11. Thus during the attempt to prepare a pyridodiazepine intermediate, beside a very small ...