Concentrated hydrochloric acid was added to a solution of methyl 6-(benzenesulphonylmethyl)-2-(3-t-butoxycarbonylaminopropyl)-3-(furan-3-yl)benzoate (Intermediate 131) in 1,4-dioxane (8 ml) and water (2 ml) and the mixture was stirred for 30 minutes. This was evaporated to dryness and the residue was purified by chromatography on silica eluting with a mixture of DCM:MeOH:AcOH:water (120:15:3:2) to give methyl 2-(3-aminopropyl)-6-(benzenesulphonylmethyl)-3-(furan-3-yl)benzoate as a colourless gum. This material was dissolved in a mixture of dioxane and water (3:1) and lithium hydroxide monohydrate (0.188 g) was added. The reaction was heated in the microwave at 150° C. for one hour. After cooling, concentrated hydrochloric acid was added and the mixture was evaporated to dryness. The residue was purified by chromatography on silica eluting with a mixture of DCM:MeOH:AcOH:water (240:20:3:2), then again with DCM:MeOH:AcOH:water (120:15:3:2). The volume of the product containing fractions was reduced to 5 ml by evaporation and concentrated hydrochloric acid (1 ml) was added to the mixture. The mixture was evaporated to dryness and the residue was triturated with diethyl ether and the solid was collected by filtration and dried under vacuum at 60° C. to give 2-(3-aminopropyl)-6-(benzenesulphonylmethyl)-3-(furan-3-yl)benzoic acid hydrochloride (0.045 g), as a white solid.
