The reaction of Horner-Emmons reactant carbanions with 2-acetyl-5-methyl furan 1 and 2-acetyl-5-bromothiophene 9 resulted in phosphorus-containing fused bicyclic 5,5-membered and 5,6-membered systems 5a-c and 12a-c, respectively, as major reaction products along with minor (∼20%) amounts of phosphorylated heterocycles 3a-c and 10a-c. Further treatment of bromo-substituted bicyclic systems 12a-c with the corresponding carbanion proceeded as a substitution of bromine for the residue of the Horner-Emmons reactant to afford compounds 13a-c bearing endo- and exocyclic phosphorus atoms. Reaction of diethyl vinylphosphonate with 5-methylfuran 1 and 5-bromothiophene 9 provided spirofuran 8 as a sole reaction product and (5H-thieno[3,2-d]oxaphosphinin-2-yl)vinylphosphonate 15, respectively. Among the products, at 50 mg/kg dose, 4 compounds showed notable anti-inflammatory activity without toxicity side-effect.