A CONVENIENT ENTRY TO NEW C-7-MODIFTED COLCHICINOIDS THROUGH AZIDE ALKYNE [3+2] CYCLOADDITION: APPLICATION OF RING-CONTRACTIVE REARRANGEMENTS

摘要

Reliable procedures for the preparation of azides derived from colchicine (1), allocolchicine (3) and N-acetylcolchinol (4a) were developed. These azides were then employed in Cu-catalyzed Huisgen-Sharpless [3+2] cycloaddition ("click") reactions with alkynes under microwave irradiation. The method developed opens a convenient and efficient access to libraries of new C-7-modified colchicinoids (triazole derivatives). In addition, a plausible mechanistic rationale for the colchicine-allocolchicine rearrangement is suggested.