Solid-State Conformation of a Hybrid Tripeptide between .BETA.-Amino Acid; 8-Aminocyclooct-4-enecarboxylic Acid and 2-Aminoisobutyric Acid.

An eight-membered cyclic beta-amino acid, 8-aminocyclooct-4-enecarboxylic acid, was designed as a conformationally restricted non-proteinogenic amino acid. A hybrid tripeptide containing this eight-membered cyclic beta-amino acid and 2-aminoisobutyric acids was synthesized by conventional solution methods. The conformation of the tripeptide was studied using X-ray analysis and was shown to form an eleven-membered hydrogen-bonded turn (3(11)-helical structure) in the solid state.