Trifluoroacetic acid → 8-[4-({(2S,5R)-5-[(R)-hydroxy(phenyl)methyl]pyrrolidin-2-yl}methyl)benzoyl]-2-oxa-8-azaspiro[4.5]decan-1-one

To a solution of 28 mg (0.05 mmol) of the title compound from Step A above in 1 ml anhydrous dichloromethane at ambient temperature was added 0.3 ml trifluoroacetic acid. The solution was stirred for 1 h. It was then evaporated and purified by reverse-phase HPLC (TMC Pro-Pac C18; 5-65% 0.1% trifluoroacetic acid in acetonitrile/0.1% trifluoroacetic acid in water gradient). The pure fractions were lyophilized overnight to give 18 mg (80%) of the title compound as a white solid. LC/MS 449.2 (M+1). 1H NMR (DMSO): δ 7.27-7.32 (m, 8H), 7.19-7.22 (m, 1H), δ 5.15 (bs, 1H), δ 4.28 (t, J=6.8 Hz, 2H), δ 4.23 (d, J=7.2 Hz, 1H), δ 4.20 (bs, 1H), δ 3.60 (bs, 1H), δ 3.27 (t, J=7.0 Hz, 1H), δ 3.21 (m, 2H), δ 3.11 (q, J=7.1 Hz, 1H), δ 2.71 (qd, J=13.1, 6.8 Hz, 2H), δ 2.23 (s, 2H), δ 1.52-1.65 (m, 5H), δ 1.38-1.44 (m, 1H), δ 1.28-1.34 (m, 2H).