Synthesis and In Vitro Antitumor Evaluation of Some New Pyrimido[4,5‐b]quinoxaline 5,10‐Dioxide Derivatives

A new series of tricyclic pyrimidoquinoxaline derivatives were synthesized and evaluated as antitumor assays and compared with standard drug 5-fluorouracil. These new pyrimidoquinoxaline derivatives were synthesized by the reaction with o-aminonitrilequinoxaline derivative 3 with various reagents. One from which, the condensation of o-aminonitrile with potassium cyanate in acetic acid was stated as a new procedure for building the pyrimidine ring incorporate to quinoxaline moiety. Further condensation of aminonitrile 3 with formamide or Vilsmeier reaction followed by transamination or carbon disulphide was applied as procedures for the pyrimidine ring syntheses. Compound 15 achieved significant in vitro antitumor activity, and compounds 9 and 14 have high activities.