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While under an argon atmosphere, a solution of 1,2-bis(diphenylphosphino)ethane (306 mg, 0.77 mmol) and chloro-1,5-cyclooctadiene iridium (I) dimer (258 mg, 0.39 mmol) in anhydrous THF (30 mL) was treated with 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (1.48 g, 1.67 mL, 11.6 mmol) in one portion. After stirring for 15 minutes the solution was cooled to 5° C. (ice-water batch) and treated with benzyl 4-(2-acetamido-1-(tert-butylamino)-1-oxohex-5-en-2-yl)piperidine-1-carboxylate (3.42 g, 7.70 mmol) in one portion. After the addition was complete, the cooling bath was removed and the reaction mixture was allowed to warm up to room temperature. After 2 hours of stirring the reaction was quenched with saturated aqueous sodium bicarbonate (50 mL) and extracted using ethyl acetate (2×150 mL). The organic layer was dried over MgSO4, filtered and concentrated. MPLC purification (100 g column, 40-80% ethyl acetate in heptane) gave benzyl 4-(2-acetamido-1-(tert-butylamino)-1-oxo-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)hexan-2-yl)piperidine-1-carboxylate as a colorless oil (3.10 g, 71% yield). 1H NMR (CDCl3, 300 MHz) δ 7.36-7.30 (m, 5H), 6.94 (bs, 1H), 5.46 (s, 1H), 5.10 (s, 2H), 4.36-4.10 (m, 2H), 2.86-2.60 (m, 3H), 2.40-2.28 (bt, J=12.3 Hz, 1H), 1.98 (s, 3H), 1.78-1.61 (m, 2H), 1.49-1.17 (m, 5H), 1.33 (s, 9H), 1.20 (s, 8H), 1.12-0.94 (m, 2H), 0.73 (t, J=7.8 Hz, 2H).

1. additionAfter the addition
2. customthe cooling bath was removed
3. stirringAfter 2 hours of stirring the reaction
4. customwas quenched with saturated aqueous sodium bicarbonate (50 mL)
5. extractionextracted
6. dry with materialThe organic layer was dried over MgSO4
7. filtrationfiltered
8. concentrationconcentrated
9. customMPLC purification (100 g column, 40-80% ethyl acetate in heptane)