A 22-L four-neck round bottom flask equipped with mechanical stirrer, heating mantel, temperature probe, nitrogen inlet, and a reflux condenser with nitrogen outlet was purged with nitrogen for 30 min before use. The product of Step C (603.5 g, 1.46 mol, 1 eq), AIBN (241 g, 1.46 mol, 1 eq), tris(trimethylsilyl)silane (910 mL, 2.93 mol, 2 eq) and toluene (16.3 L) were added and the suspension was degassed with nitrogen purge through the suspension for 20 min. The reaction was heated to 80-83° C. for 1 h after which time the heat was shut off, and the reaction cooled to rt over 12-18 h. TLC showed the reaction was complete. The reaction was poured directly into a BIOTAGE dry 5-kg column that was eluted with 16 L of 50% EtOAc in heptane, followed by 32 L of EtOAc and provided the product of Step D of a golden thick oil, which slowly crystallized on standing. 1H NMR (CHLOROFORM-d) δ: 4.64 (brd. s, 1H), 4.07-4.25 (m, 2H), 3.89 (ddd, J=8.8, 7.2, 4.5 Hz, 1H), 3.53-3.67 (m, 3H), 2.17 (dd, J=13.3, 6.2 Hz, 1H), 1.98-2.06 (m, 1H), 1.86-1.97 (m, 1H), 1.68-1.81 (m, 2H), 1.46-1.56 (m, 2H), 1.44 (s, 9H). Calculated for C13H23NO4: 202.2 (M−55). found: 202.2.
