3-Substituted 2-isocyanopyridines as versatile convertible isocyanides for peptidomimetic design.

We report the use of 3-substituted 2-isocyanopyridines as convertible isocyanides in Ugi four-component reactions. The N-(3-substituted pyridin-2-yl)amide Ugi products can be cleaved by amines, alcohols, and water with Zn(OAc)2 as a catalyst. In addition, the applicability of the method was demonstrated in constrained di-/tripeptides bearing acid and base sensitive protective groups obtained via Ugi-4CR post-condensation modifications.