Scheme 3.

Synthesis of A-ring-condensed 3′-substituted isoxazoles by FGI. Reagents and conditions: (i) NaBH₄, MeOH, RT, 1 h; (ii) LiOH, THF/H₂O, RT, 2–24 h; (iii) DAST, DCM, RT, 1–2 h; (iv) DMP, DCM, RT, 2 h; (v) NaOH, MeOH/DCM, RT, 1–20 h; (vi) MeOH, H₂SO₄, reflux, 36 h; (vii) NH₃/MeOH (6M), RT, 4 h. (viii) DPPA, toluene, reflux, overnight; (ix) DDQ, PPh₃, with or without the addition of Et₃N, DCM, RT, 1 h; (x) NH₂OH (50 wt. % aq. solution), Na₂CO₃, EtOH, reflux, overnight; (xi) DIAD, PPh₃, ACN, 1 h.