Reaction Steps
To a solution of N′-((2R,3S)-2-(7-cyanobenzo[b]thiophen-4-ylamino)-3-hydroxybutanoyl)-4-fluorobenzohydrazide (0.53 g, 1.29 mmol) in THF (90 mL) was added PS-BEMP (1.76 g, 3.87 mmol, ˜2.2 mmol/g) and p-TsCl (265 mg, 1.39 mmol) at room temperature. The mixture was stirred at room temperature for 8 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)-1-(5-(4-fluorophenyl)-1,3,4-oxadiazol-2-yl)-2-hydroxypropylamino)benzo[b]thiophene-7-carbonitrile (139 mg, 27%) and the dehydration product 4-(1-(5-(4-fluorophenyl)-1,3,4-oxadiazol-2-yl)prop-1-enylamino)benzo[b]thiophene-7-carbonitrile (8 mg, 2%). Title compound: 1H NMR (400 MHz, Acetone-d6, δ in ppm) 8.03 (dd, J=5.3, 8.8 Hz, 2H), 7.88 (d, J=5.7 Hz, 1H), 7.73 (d, J=5.7 Hz, 1H), 7.63 (d, J=8.2 Hz, 1H), 7.32 (t, J=8.8 Hz, 2H), 6.83 (d, J=8.2 Hz, 1H), 6.48 (d, J=8.4 Hz, 1H), 5.20 (dd, J=4.7, 8.4 Hz, 1H), 4.78 (b, 1H), 4.63 (m, 1H), 1.41 (d, J=6.4 Hz, 3H). Dehydration product: 1H NMR (400 MHz, Acetone-d6, δ in ppm) 8.11 (dd, J=5.3, 8.6 Hz, 2H), 7.96 (d, J=5.6 Hz, 1H), 7.80 (d, J=5.6 Hz, 1H), 7.62 (d, J=8.2 Hz, 1H), 7.37 (t, J=8.6 Hz, 2H), 7.01 (q, J=7.1 Hz, 1H), 6.57 (d, J=8.2 Hz, 1H), 1.93 (d, J=7.1 Hz, 3H).
