Scheme 3. Reagents and conditions used to synthesize III-15(a–o). (i) 4-methoxy-N-methylaniline, PyBop, DIEA, CH₂Cl₂, r.t., 8–10 h; (ii): CF₃COOH; CH₂Cl₂, r.t., 5–6 h; (iii) 3-ethynylbenzoic acid, HATU, DIEA, CH₂Cl₂, r.t., 10 h; (vii): azide substituents; CuSO₄·5H₂O, VcNa, THF/H₂O (v : v = 1 : 1), 30–60 °C, 4–6 h.