1.1: sodium hydroxide / 20 °C 1.2: pH 5 2.1: 1-propanephosphonic acid cyclic anhydride / ethyl acetate / 2 h / 20 - 50 °C 3.1: hydrogen; acetic acid / 5 palladium on charcoal / ethanol / 24 h / 50 °C / 3750.38 Torr / Inert atmosphere 3.2: 20 °C 4.1: potassium carbonate / ethanol; water; acetone / 0.33 h / 28 - 32 °C View Scheme