4-Methyl-4a-phenyl-9c-(phenylcarbonyl)-4,4a,9b,9c-tetrahydro-1H-[1]benzo thieno[2,3-b]furo[3,4-d]-pyrrole-1,3(3aH)-dione having an intriguing U-shaped configuration, synthesized by 1,3-dipolar cycloaddition reaction between the 3,4-dimethyl-2-phenyl-1,3-oxazolium-5-olate and 3-(phenylcarbonyl)-2H-thiochromen-2-one, has been studied at computational and NMR experimental level to investigate its capacity to bind metal cations. Both experimental and theoretical studies demonstrated that this compound can form moderately stable complexes with potassium cation and then could act as ionophore for sensor applications. (C) 2011 Elsevier B.V. All rights reserved.