Novel oxazolxanthone derivatives as a new type of α-glucosidase inhibitor: synthesis, activities, inhibitory modes and synergetic effect.

•A series of novel oxazolxanthones 4–21 were synthesized as α-glucosidase inhibitors.•Most of the compounds showed excellent anti-α-glucosidase activity.•Both competitive (compound 4) and non-competitive (compounds 15, 16 and 20) manners were observed.•Compounds 15, 16 and 20 may function in the noncompetitive domain of the enzyme.•Synergistic inhibition of compounds 16 and 20 was predicted by Molecular docking and confirmed by experiment.