Synthesis and Evaluation of 2‐{[(2‐Oxo‐1H‐quinolin‐8‐yl)oxy]methyl}‐Substituted α‐Methylidene‐γ‐butyrolactones

O‐Alkylation of 8‐hydroxy‐1H‐quinolin‐2‐one (1) afforded 8‐(2‐oxopropoxy)‐1H‐quinolin‐2‐one (2) which was immediately cyclized to form the tricyclic 2,3‐dihydro‐3‐hydroxy‐3‐methyl‐5H‐pyrido[1,2,3‐de][1,4]benzoxazine,‐5‐one (3). The Reformatsky‐type condensation of 3 furnished antiplatelet 8‐[(2,3,4,5‐tetrahydro‐2‐methyl‐4‐methylidene‐5‐oxofuran‐2‐yl)melhoxy]‐1H‐quinolin‐2‐one (4). Its counterparts 7a–f, Ph‐substituted at C(2) of the furan ring, were obtained from 1 via alkylation and the Reformatsky‐type condensation. Although compound 4 was less active against platelet aggregation than 7a–f, it was the only compound which exhibited significant inhibitory activity on high‐K+ medium, Ca2+‐induced vasoconstriction and was more active than most of its Ph‐substituted counterparts against norepinephrine‐induced vasoconstrictions.