Synthesis of novel 1,4‐dihydropyrido[3′,2′:5,6]thiopyrano[4,3‐c]‐pyrazoles and 5H‐pyrido[3′,2′:5,6]thiopyrano[4,3‐d]pyrimidines as potential antiproliferative agents

The synthesis of new planar derivatives characterized by the presence of a pyridothiopyranopyrazole or pyridothiopyranopyrimidine nucleus, carrying a substituted aryl group, is reported. The novel 1,4‐dihydropyrido3′,2′:5,6]thiopyrano4,3‐c]pyrazole derivatives were obtained by condensation of 2,3‐dihydro‐3‐hydroxymethylenethiopyrano2,3‐b]pyridin‐4(4H)‐ones with appropriate hydrazines. The preparation of 2‐substituted pyrido3′,2′:5,6]thiopyrano4,3‐d]pyrimidines was accomplished from the intermediate 2,3‐dihy‐dro‐3‐dimethylaminomethylenethiopyrano2,3‐b]pyridin‐4(4H)‐ones by reaction with the appropriate binucleophile amidines. The antiproliferative activity of some new products was tested by an in vitro assay on human tumour cell lines (HL‐60 and HeLa), but none of them showed any significant effects in the tests performed. Accordingly, linear flow dichroism measurements indicated their inability to form a molecular complex with DNA.