To a solution of 2-(2-isopropyl-5-methyl-2H-[1,2,4]triazol-3-yl)-4,5-dihydro-6-oxa-1,3a-diazabenzo[e]azulen-8-ol from Example 4 (2.8 g, 8.5 mmol), 4-bromo-2-hydroxybutyric acid methyl ester (2.5 g, 12.7 mmol) and triphenylphosphine (3.77 g, 14.3 mmol) in dioxane (30 mL) was added DIAD (2.8 ml, 14.3 mmol) and the reaction mixture was stirred at RT for 1 h. Additional amounts of DIAD (1.67 mL) and of triphenylphosphine (2.23 g) were added and stirring was continued for 1 h. The mixture was diluted with EtOAc and washed with aq. NaOH (1N). The aqueous phase was further extracted with EtOAc (×3). The combined organic layers were then washed with brine, dried and concentrated in vacuo. The resulting residue was purified by column chromatography (Si-PCC, gradient 0-10% MeOH in EtOAc followed by Si-PCC, gradient 0-10% MeOH in DCM) affording 4-Bromo-2-[2-(2-isopropyl-5-methyl-2H-[1,2,4]triazol-3-yl)-4,5-dihydro-6-oxa-1,3a-diazabenzo[e]azulen-8-yloxy]butyric acid methyl ester (2.5 g, 58%). 1H NMR (CDCl3, 400 MHz): δ 8.43 (1H, d, J=9.01 Hz), 7.57 (1H, s), 6.74 (1H, d, J=9.15 Hz), 6.55 (1H, d, J=2.56 Hz), 5.95-5.83 (1H, m), 4.92 (1H, dd, J=8.80, 3.97 Hz), 4.51-4.31 (4H, m), 3.79 (3H, s), 3.65-3.53 (2H, m), 2.58-2.36 (5H, m), 1.58-1.51 (6H, m)
