A mixture of Intermediate 7 (250 mg, 0,83 mmol) and 2-({[(1,1-dimethylethyl)oxy]carbonyl}amino)benzoic acid (196 mg, 0.83 mmol, e.g. available from Fluka) in N,N-dimethylformamide (4 ml) was treated with N,N-diisopropylethylamine (0.569 ml, 3.3 mmol) and (1H-1,2,3-benzotriazol-1-yloxy)(tri-1-pyrrolidinyl)phosphonium hexafluorophosphate (472 mg, 0.91 mmol) and allowed to stir at room temperature for 4 hours. An additional portion of (1H-1,2,3-benzotriazol-1-yloxy)(tri-1-pyrrolidinyl)phosphonium hexafluorophosphate (0.5 equiv., 0.41 mmol) was added and the mixture stirred for an additional hour. The solvent was evaporated and the residue dissolved in ethyl acetate (50 ml) and washed with aqueous sodium bicarbonate solution (2×50 ml); the organic fraction was dried (Na2SO4) and evaporated. The residue was purified by chromatography on silica gel (50 g SPE cartridge), eluting with a gradient of 0-100% ethyl acetate/cyclohexane followed by a gradient of 0-20% methanol/ethyl acetate over 40 minutes. Fractions containing product were pooled and evaporated to give the title compound (292 mg). LCMS showed MH+=523; TRET=2.71 min.
