Scheme 1

(a) SOCl₂, MeOH, NaHCO₃, Reflux, 8 h; (b) TFA, CH₂Cl₂, RT, 24 h; (c) KMnO₄,THF, RT, 12 h; (d) NaOH, MeOH, Reflux,12 h; (e) TBTU, NEt₃, DMF, RT, 4 h; (f) DMF, RT, 30 min; (g) Et₃N, H₂O/t-BuOH, RT, 1 h; (h) CuSO₄.5H₂O, Sodium Ascorbate, RT, 20–27 h.