As a part of the development of conformational guidelines for the design of metabolically altered peptidomimetics, we present conformational energy calculations on model dipeptide compounds with glycine (Gly), L-alanine (Ala), r-aminoisobutyric acid (Aib), L-terr-butylglycine (Tle), L-phenylglycine (Phg), (.,a)diphenylglycine (Dqg), L-2-aminobutyric acid (Abu), 2-amino-2-ethylbutync acid (Deg), ~-2-amino-2vinylacetic acid (Ava) and (%,a)-divinylglycine (Dvg). The energy calculations have been made using molecular mechanics methods with a force field derived from MM2. The salient features are expressed in terms of conformational energy plots, drawn as a function of the backbone torsion angles $(Ci-1-Ni-C;-CI) and $(Ni-C;-CLN, + 1). The low-energy structures of these compounds are qualitatively consistent with the X-ray crystal structure analyses of peptides and peptidomimetics. They are also in agreement with the results of the solution-phase studies carried out by NMR and IR techniques. The results obtained have important implications in the design of conformationally restricted peptidomimetics. 0 Munksgaard 1995.