1,1′-(Azodicarbonyl)dipiperidine (0.18 g, 0.7 mmol) was added to a solution of methyl 3-(5-hydoxylindolyl)-2-benzylpropanoate (0.12 g, 0.39 mmol), as prepared in the preceding step, 2-(3-hydroxypropyl)aminopyridine (0.07 g, 0.47 mmol), as prepared instep b of Example 1, and tri-n-butylphosphine (0.14 g, 0.7 mmol) in tetrahydrofuran (6.0 mL). After stirring at ambient temperature overnight (16 h), the reaction was concentrated in vacuo and the residue purified by flash chromatography on silica gel (10%-50% ethyl acetate in hexane) to give the title compound as a yellow oil (0.064 g, 38%). 1H-NMR (400 MHz, CDCl3) δ 8.08 (br s, 1H), 7.40 (m, 1H), 7.37 (m, 1H), 7.22 (m, 2H), 7.00 (m, 3H), 6.84 (dd, J=8.9, 2.4 Hz, 1H), 6.54 (m, 1H), 6.40 (d, J=8.4 Hz, 2H), 6.36 (d, J=3.1 Hz, 1H), 4.77 (br s, 1H), 4.40 (m, 1), 4.17 (m, 3H), 3.52 (m, 5H), 3.24 (m, 1), 3.08 (m, 1H), 2.76 (m, 1H), 2.11 (m, 2H).
