The title compound of Example 43 (58.8 mg, 121 μmol) was treated with tBuOH (2 mL), diphenylphosphoryl azide (70 mg, 254 μmol) and triethylamine (60 mg, 592 mmol). The reaction was heated at 90° C. for 3 hours and cooled to rt. HPLC-MS analysis indicated that the Curtius rearrangement had occurred, but that the intermediate isocyanate had been hydrolyzed to the carbamic acid and activated as the azide rather than being intercepted by the alcohol. The solvent was removed and the reaction was extractively worked up with ethyl acetate and water, dried over MgSO4 and rotary evaporated. The residue was treated with concentrated ammonia and allowed to stir overnight. The reaction was again extractively worked up and then chromatographed on silica gel using DCM an MeOH as eluent to afford the title material (12 mg, 20%); 1H NMR (CDCl3, 400 MHz) δ 0.88 (d, 3H, J=6.3), 0.91 (d, 3H, J=6.3), 1.55-1.80 (m, 4H), 1.85-1.95 (m, 1H), 2.37 (s, 3H), 2.90-3.03 (m, 3H), 3.06-3.26 (m, 2H), 3.37 (dd, 1H, J1=8.7, J2=17.1), 3.48-3.61 (m, 2H), 4.01-4.26 (m, 1H), 4.26-4.38 (m, 1H), 4.50 (dd, 1H, J1=7.7, J2=15.0), 6.00-6.20 (m, 1H), 6.49 (dd, 1H, J1=4.0, J2=8.4), 6.74 (ddd, 1H, J1=2.5, J2=J3=8.9), 6.78-6.83 (m, 1H), 7.16-7.20 (m, 1H), 7.23-7.37 (m, 3H), 7.50-7.57 (m, 2H).
