On the stabilization of the syn-rotamer of amino acid carbamate derivatives by hydrogen bonding

The syn-rotamers of carbamate derivatives of α-amino acids are shown to be stabilized by the formation of H-bond complexes with carboxylic acid moieties in solution. This effect is, as expected, concentration and temperature dependent. Thermodynamic parameters (both ΔG° and ΔG‡) for N-Boc-alanine were determined by NMR in the ±60 °C range.