This study reports the first synthesis of seven novel heterocyclic coumarin annulates, each containing a five-membered heterocycle with four heteroatoms (three oxygen and one sulfur) in a linear arrangement. The synthesis aimed to develop readily available coumarin frameworks with diverse biological properties. Structural confirmation was achieved through 1H-NMR, 13C-NMR, and FTIR. The annulates were evaluated in vitro for their potential as antioxidants, anti-inflammatories, antidiabetics, anticancer agents, and antimicrobials. Additionally, their biosafety toward non-tumor cells and commensal bacteria was assessed. Computer-aided tools were used to analyze toxicity and pharmacokinetics. The results showed promising biological activities: HCl exhibited strong anti-inflammatory effects via lipoxygenase pathway and significant antifungal activity surpassing nystatin. HCl2 showed potential as an antioxidant, anticancer, and biosafe compound. HCl3 demonstrated strong antibacterial activity against aerobic bacteria, comparable to ciprofloxacin. All annulates, especially HCl3, showed good biosafety. HCl6 and HCl7 showed strong inhibitory activity against glucosidase and amylase, indicating potential as antidiabetic agents. The annulates also showed favorable toxicity and oral bioavailability. These findings suggest that these annulates could serve as valuable frameworks for developing new drugs with broad bioactivity in the future. Keywords: Annulation; Biosafety; Coumarin; Drug-likeness; Heterocycle; Multiactivity.This study reports the first synthesis of seven novel heterocyclic coumarin annulates, each containing a five-membered heterocycle with four heteroatoms (three oxygen and one sulfur) in a linear arrangement. The synthesis aimed to develop readily available coumarin frameworks with diverse biological properties. Structural confirmation was achieved through 1H-NMR, 13C-NMR, and FTIR. The annulates were evaluated in vitro for their potential as antioxidants, anti-inflammatories, antidiabetics, anticancer agents, and antimicrobials. Additionally, their biosafety toward non-tumor cells and commensal bacteria was assessed. Computer-aided tools were used to analyze toxicity and pharmacokinetics. The results showed promising biological activities: HCl exhibited strong anti-inflammatory effects via lipoxygenase pathway and significant antifungal activity surpassing nystatin. HCl2 showed potential as an antioxidant, anticancer, and biosafe compound. HCl3 demonstrated strong antibacterial activity against aerobic bacteria, comparable to ciprofloxacin. All annulates, especially HCl3, showed good biosafety. HCl6 and HCl7 showed strong inhibitory activity against glucosidase and amylase, indicating potential as antidiabetic agents. The annulates also showed favorable toxicity and oral bioavailability. These findings suggest that these annulates could serve as valuable frameworks for developing new drugs with broad bioactivity in the future. Keywords: Annulation; Biosafety; Coumarin; Drug-likeness; Heterocycle; Multiactivity.