Infrared spectra of protected amino acids, N-benzoxycarbonyl-L-proline and N-benzoxycarbonyl-L-isoleucine were measured in the gas phase from 10 to 3 mu m. 4 and 3 conformers were found, respectively. The spectra in the 3 mu m region reveal the carboxylic OH and amide NH bonds do not participate in hydrogen bonding with neighboring amide groups despite the highest acidity in the molecule. The spectra ill the 10-5 mu m region imply the main chain structure is the same among the conformers.