Reaction Steps
Solid TBDMS Chloride (8.22 g, 54.44 mmol) was added in one portion to a solution of 170 (7.23 g, 24.74 mmol) and imidazole (8.42 g, 123.72 mmol) in anhydrous DMF (75 mL) and allowed to stir at room temperature for 16 h. The reaction mixture was poured into water (500 mL) and filtered to afford the crude product (171), which was purified by recrystallisation from EtOH (800 mL) as fine white needles (6.995 g, 17.21 mmol, 70%). 1H NMR (270 MHz, CDCl3) δ10.06 (s, 1H, NH), 7.37 (s, 1H, ArH), 6.68 (s, 1H, ArH), 4.19-4.14 (m, 1H, 2), 4.06-4.01 (m, 1H, 11a), 3.90 (s, 3H, OMe), 3.88 (s, 3H, OMe), 3.69-3.63 (m, 2H, 3), 2.85-2.80 (m, 1H, 1), 2.05-2.01 (m, 1H, 1); 13C NMR (67.8 MHz, CDCl3) δ170.4, 170.2, 165.9, 152.1, 145.8, 145.6, 131.1, 130.7, 118.1, 111.9, 104.3, 104.1, 69.2, 69.1, 56.0, 55.9, 55.7, 54.3, 54.0, 35.0, 25.8, 25.7, 25.6, 17.9, −3.0, −3.5, −4.9, −5.0.
