Reaction Steps
To a solution of N′-((2R,3S)-2-(7-cyanobenzo[b]thiophen-4-ylamino)-3-hydroxybutanoyl)benzohydrazide (0.69 g, 1.75 mmol) in THF (100 mL) were added PS-BEMP (2.39 g, 5.27 mmol, ˜2.2 mmol/g) and p-TsCl (353 mg, 1.85 mmol) at room temperature. The mixture was stirred at room temperature for 14 h, then methanol (5 mL) was added to quench the reaction. The resin was filtered and washed with MeOH. The combined filtrate was concentrated to give a residue, which was purified by flash chromatography to afford the title compound 4-((1R,2S)-2-hydroxy-1-(5-phenyl-1,3,4-oxadiazol-2-yl)propylamino)benzo[b]thiophene-7-carbonitrile (167 mg, 25%) as a foam and the dehydration product 4-(1-(5-phenyl-1,3,4-oxadiazol-2-yl)prop-1-enylamino)benzo[b]thiophene-7-carbonitrile (33 mg, 5%). Title compound: 1H NMR (400 MHz, Acetone-d6, δ in ppm) 7.98 (m, 2H), 7.88 (d, J=5.7 Hz, 1H), 7.72 (d, J=5.7 Hz, 1H), 7.63 (d, J=8.2 Hz, 1H), 7.51˜7.57 (m, 3H), 6.85 (d, J=8.2 Hz, 1H), 6.50 (d, J=8.4 Hz, 1H), 5.22 (dd, J=4.7, 8.4 Hz, 1H), 4.80 (b, 1H), 4.65 (m, 1H), 1.42 (d, J=6.4 Hz, 3H). Dehydration product: 1H NMR (400 MHz, Acetone-d6, δ in ppm) 8.05 (m, 2H), 7.95 (d, J=5.6 Hz, 1H), 7.78 (d, J=5.6 Hz, 1H), 7.55˜7.62 (m, 4H), 7.01 (q, J=7.1 Hz, 1H), 6.57 (d, J=8.4 Hz, 1H), 1.93 (d, J=7.1 Hz, 3H).
