To a solution of the subtitle product of step i) (2.0 g) in dry DMF (20 ml) at 0° C. was added 60% sodium hydride (0.9 g) portionwise over 5 min. After further stirring at 0° C. for 30 min the subtitle product from step iii) (3.6 g) in DMF (10 ml) was added and the whole allowed to stir at room temperature for 24 h. The reaction mixture was carefully quenched with aqueous 2M hydrochloric acid until pH 7.4. The solvent was evaporated to dryness and the residue dissolved in a mixture of methanol/EtOAc and applied to an SCX column followed by further elution with EtOAc. This was then followed by elution with EtOAc/triethylamine mixtures and these fractions evaporated to dryness. The subtitle compound was obtained pure by trituration with Et2O and filtration, leaving a white solid. Yield: 1.5 g.
