Direct synthesis of β^2,3‐amino acid from β‐hydroxycarbamides: Implication in the synthesis of azumamide analogs and conformational analysis

Abstract

The designed β^2,3 unnatural amino acids have been synthesized from α‐methyl‐β‐hydroxycarbamides via direct azidation without obtaining eliminated products. Furthermore, these β^2,3 amino acids were utilized to synthesize cyclic tetrapeptides (CTPs) as azumamide analogs. 2D‐NMR analysis revealed the compact secondary structure as a single conformer. Presence of intramolecular H‐bonding in CTPs was observed in this α₃β^2,3 architecture and displayed a seven‐membered γ‐turn structure.