Triisopropylsilyl trifluoromethanesulfonate (327 mg, 1.06 mmol) was added to a solution of Intermediate 28a (210 mg, 0.89 mmol) and Et3N (135 mg, 1.33 mmol) in a DMF (3 mL) and the mixture stirred at RT for 1 h. The reaction mixture was applied to an SCX-2 cartridge (25 g) and washed with MeOH. The product was eluted with 2M NH3 in MeOH; concentration in vacuo gave a residue. FCC, using 0-10% [2M NH3 in MeOH] in DCM, gave the title compound (110 mg, 31%). LCMS (Method 1): Rt 4.45 min, m/z 393 [MH+].
