To a stirred solution of 9-1 (4.9 g, 14.2 mMol) and 8-5 (4.2 g, 15.6 mMol) in NMP (50 mL) was added triethylamine (6 mL, 42.6 mMol) followed by acetic acid (1.6 mL, 28.4 mMol). After stirring at ambient temperature overnight, sodium triacetoxyborohydride (3.6 g, 17 mMol) was added in portions. Upon completion, the reaction was diluted with ethyl acetate and washed with saturated NaHCO3, followed by water, then brine. The organic layer was dried with Na2SO4 and MgSO4, filtered and concentrated in vacuo. The crude residue purified using flash chromatography on silica (gradient: 0% to 10% MeOH in CHCl3 over 25 min) to yield 9-2 as an orange solid. LC/MS (M+1) calculated: 559.1; observed: 559.2
