Both methylene protons (C′H2-2,4) of the azetidine ring showed signals in the form of broadened multiplets in the region of δ 3.11–3.24 and 3.64–3.71 ppm, and the methine proton (C′H-3) appeared as a multiplet in the region of δ 4.10–4.35 ppm. A relatively broad peak of ...