Expedient solid-phase synthesis of putative β-turn mimetics incorporating the i + 1, i + 2, and i + 3 sidechains

A number of putative β-turn mimetics that incorporate sidechain functionality at the i + 1, i + 2, and i + 3 positions were synthesized on solid support in high levels of purity and in good overall yields from readily available starting materials. A variety of sidechain functionality, ring sizes, and sidechain stereochemistries were introduced demonstrating the generality of the synthesis method. A significant feature of the synthesis sequence is the use of guanidine resin that functions as both a solid-phase extraction resin and a support-bound general base catalyst.