Study of the conformational profile of selected unnatural amino acid residues derived from L-phenylalanine

The present work reports the results of a conformational study performed on seven unnatural amino acid residues and on its natural precursor, investig ated by means of computational methods at the molecular mechanics level. Am ino acid residues selected for the present study are derivatives of L-pheny lalanine substituted at the alpha and/or beta carbons. This series is compo sed of different linear analogs, including alpha-methyl, beta-methyl and be ta-phenyl substituted with different stereochemistry. Analysis of the Ramac handran maps of the corresponding dipeptides in vacuo reveals their conform ational preferences, to be used as guidance for the synthesis of constraine d peptide analogs with desired conformational propensities. The available c onformational space for every dipeptide is also analysed. Copyright (C) 199 9 European Peptide Society and John Wiley & Sons, Ltd.