Fig. 2. Synthesis of the ligands 1 and 2. Reagents, conditions, and yields: (a); SeO2, 1,4-dioxane/H2O, reflux, 1 h, 80% (b) Ohira–Bestmann reagent (compound 2), K2CO3, MeOH, RT, 3 h, 38%; (c); NaN3, EtOH/H2O, 98 °C, 12 h, 68%; (d) (i) iso-butyl-chloroformate, N-methyl morpholine, THF, −10 °C, 10 min. (ii) NaBH4, MeOH, −10 °C, 50 min, 47%; (e) TosCl, DMAP, CH2Cl2, RT, 3 h, 72%; (f) NaN3, DMF, 80 °C, 24 h, 65%; (g) (i) LiOH, THF/MeOH/H2O, RT, 1 h (ii) HCl in 1,4-dioxane, RT, 1 h, 78%; (h) Cu(ii)-TBTA, Na-Ascorbate, DIPEA, CH2Cl2/H2O, RT, 72 h, 70% for the ligand 1, 88% for the ligand 2.
