The product from step (d) (0.38 g, 1.23 mmol) was dissolved in anhydrous tetrahydrofuran (100 ml) and triphenylphosphine (1.062 g, 4.05 mmol) added. The solution was cooled to 0° C. and N-iodosuccinimide (0.912 g, 4.05 mmol) added. The reaction was allowed to warm to room temperature overnight, whilst stirring. Methylamine, as a 40% aqueous solution, (5 ml) was added and the reaction stirred for 24 h. Saturated aqueous sodium bicarbonate solution (40 ml) was added and the mixture extracted with ethyl acetate (3×70 ml). The combined extracts were washed with water (20 ml), dried (magnesium sulphate) and evaporated in vacuo. The residue was dissolved in methanol and applied to CC SCX resin. The resin was washed with methanol (200 ml) and the product liberated with 7N ammonia in methanol (100 ml). The solvent was removed in vacuo and the product converted into an oxalate salt and recrystallised from ethanol to give the title compound as a white solid (0.185 g, 37%).
