Diastereoselective one-pot synthesis of novel ABCD-fused chromeno[2,3-d]pyrazolo[3,4-b]pyridines

A new aspect concerning chromone chemistry leading to the one-pot synthesis of functionalized novel ABCD-fused chromenopyrazolopyridines has been described. The synthesis involves a multicomponent reaction of chromone-3-benzoylhydrazones with isocyanides and acetylenedicarboxylates, whereupon novel complex tetracyclic benzopyrone derivatives containing three stereogenic centres were formed. The structure elucidation of the products was accomplished by 1D and 2D NMR experiments and confirmed by X-ray crystallographic analysis. Full assignment of all 1H and 13C NMR chemical shifts has been unambiguously achieved. The reaction mechanism is also discussed. In addition, eight chromenopyrazolopyridine derivatives were tested for possible biological activity (antioxidant and lipid peroxidation inhibition).

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