Benzyl tert-butoxycarbonyl-alpha-aminoisobutyrate.

The small synthetic peptide, benzyl 2-(tert-butoxycarbonyl-amino)isobutyrate, C(16)H(23)NO(4), has the alpha-helical conformation [/varphi/ = 55.8 (2) degrees and /psi/ = 37.9 (2) degrees] observed in peptide fragments of peptaibols containing the alpha-aminoisobutyric acid (Aib) residue. The structure shows no intramolecular hydrogen bonding, which would disrupt the limited conformational freedom associated with this amino acid. Two weak intermolecular hydrogen contacts are observed.