Reaction Steps
To a cooled (−78° C.) solution of the title compound of Example 16 Step A (19.0 mg, 0.048 mmol) in THF (1 mL) was added KHMDS (0.240 mL, 0.5 M in toluene, 0.12 mmol). After 30 min, methyl 4-bromomethylbenzoate (27.0 mg, 0.12 mmol) was added, and the resultant mixture was allowed to warm slowly to room temperature over 15 h. The mixture was then quenched by addition of sat. aq. NaHCO3, and the aqueous phase was extracted with EtOAc. The organic phase was dried over anhydrous Na2SO4, and concentrated in vacuo: LCMS B, tr=2.91 min, m/z 544.1 [M+H]+. To a solution of the crude adduct obtained above in 1,4-dioxane (1 mL) was added a solution of LiOH (0.5 mL, 2.0 N in H2O, 1.0 mmol), and the resultant mixture was stirred at 50° C. for 2 h. The mixture was allowed to cool to room temperature whereupon it was quenched by the addition of 2 N aq. HCl. The aqueous phase was extracted with EtOAc, and the organic phase was dried over Na2SO4 and concentrated in vacuo. To the crude carboxylic acid obtained above were added EDC (60.0 mg, 0.31 mmol), HOBt (43.0 mg, 0.31 mmol), and β-alanine tert-butyl ester hydrochloride (50.0 mg, 0.31 mmol). The resultant mixture was dissolved in DMF (1 mL), DIEA (0.200 mL, 1.13 mmol) was added, and the reaction mixture was stirred at 50° C. for 2 h. The reaction mixture was quenched by addition of sat. aq. NH4Cl, and the aqueous phase was extracted with EtOAc. The organic phase was concentrated in vacuo, then dissolved in CH2Cl2 (1 mL) and TFA (1 mL). After 30 min, the mixture was concentrated in vacuo. Purification by reverse phase HPLC (30 to 100% CH3CN in H2O, each with 0.1% v/v TFA) provided the title compound: LCMS B, tr=2.56 min, m/z 601.2 [M+H]+; 1H NMR (500 MHz, d6DMSO) δ 8.41 (t, J=5.5 Hz, 1H), 7.84 (d, J=2.0 Hz, 1H), 7.69 (d, J=8.5 Hz, 2H), 7.56 (d, J=9.0 Hz, 1H), 7.32 (dd, J=9.0, 2.0 Hz, 1H), 7.24-7.21 (m, 4H), 6.95 (d, J=8.5 Hz, 2H), 5.62 (ABq, J=17.0 Hz, Δν=15.4 Hz, 2H), 3.70-3.64 (m, 1H), 3.41 (q, J=7.0 Hz, 2H), 2.97 (dd, J=13.5, 7.0 Hz, 1H), 0.88 (t, J=7.0 Hz, 3H), signals for one benzylic proton, the C3-methyl group, and the α-CO2H β-alanine methylene group were obscured by residual H2O and DMSO peaks.
