Triethylamine (13.9 mL, 99.7 mmol, 2.0 equiv) and diphenylphosphoryl azide (16.1 mL, 74.7 mmol, 1.5 equiv) were added sequentially to a suspension of c1 (9.63 g, 49.8 mmol, 1 equiv) in 1,4-dioxane (450 mL) at 23° C. The resulting solution was heated to reflux for 7.5 h, then benzyl alcohol (10.3 mL, 99.5 mmol, 2.0 equiv) was added and reflux was continued for an additional 16 h. The dark brown reaction mixture was cooled to 23° C. and the volatiles were removed under reduced pressure. The resulting dark brown oil was partitioned between water (300 mL) and EtOAc (2×250 mL) and the combined organic layers were dried over Na2SO4 and concentrated. The solid thus obtained was triturated with Et2O (150 mL) and was filtered through a medium frit, washed with Et2O (2×50 mL) and air-dried to give d1 (7.34 g, 49%) as an off-white powder: mp=179-180° C.; IR (cm1) 3386, 1727, 1645; 1H NMR (CDCl3) δ 2.39-2.46 (m, 2H), 2.65 (t, 2H, J=7.5), 4.97-5.07 (m, 2H), 5.21 (s, 2H), 5.73-5.87 (m, 1H), 6.10 (d, 1H, J=7.5), 7.32-7.44 (m, 5H), 7.68 (s, br, 1H), 8.06 (s, br, 1H), 12.74 (s, br, 1H); Anal. C17H18N2O3: C, H, N.
