Compound 203 (100 mg, 0.26 mmol) was dissolved in dioxane (2 mL) and cyclopentenylboronic acid (58 mg, 0.52 mmol) was added, followed by potassium carbonate (72 mg, 0.52 mmol) and water (0.40 mL). The resulting solution was degassed with nitrogen gas and Pd(PPh3)4 (18 mg, 0.016 mmol) was added. The mixture was heated at 100° C. for 1 h under nitrogen. The organic layer was separated, solid NaCl was added and the mixture was extracted with ethyl acetate. The combined organic layers were filtered through PL-Thiol MP SPE tube to remove palladium catalyst. The filtrate was concentrated and then purified by prep LC/MS using 5-95% acetonitrile in water with 0.1% formic acid. The formic acid was removed using Strata SCX SPE tube to give a desired product (Compound 238) as a free base (81 mg, 82%). 1H-NMR (400 MHz, CDCl3) δ: 1.09 (s, 9H), 1.90-2.05 (m, 2H), 2.51 (s, 3H), 2.55-2.65 (m, 2H), 2.74-2.95 (m, 7H), 3.88-4.14 (m, 4H), 5.95 (s, 1H), 6.09 (m, 1H), 7.66 (d, 1H). LCMS (+ESI) m/z 374.2 [M+H]+.
