Fifteen novel pyrazolo[3,4-b]-pyrido[4,3-d]-pyrimidine-4-ones (7a-o) were designed and have been successfully synthesized via tandem aza-Wittig and annulation reactions of the corresponding iminophosphorances 5, phenylisocyanate, and substituted phenols in 60-77% isolated yields. Their structures were clearly verified by infrared (IR), 1H NMR, electron impact-mass spectrometry (EI-MS), and elemental analysis. The results of a preliminary bioassay indicated that some compounds possess inhibition activities against the root of Brassica napus (rape) and Ech...
