Ring-constrained amino acid surrogates of formula I where R<;SUP>;1<;/SUP>;, R<;SUP>;2<;/SUP>;, R<;SUP>;3<;/SUP>;, R<;SUP>;4<;/SUP>;, R<;SUP>;5<;/SUP>;, R<;SUP>;6a<;/SUP>;, R<;SUP>;6b<;/SUP>;, R<;SUP>;7<;/SUP>;, and y are as defined in the specification, methods for synthesizing ring-constrained amino acid surrogates of formula I, methods of use of ring-constrained amino acid surrogates of formula I, including use in linear or cyclic compounds which include a plurality of amino acid residues and one or more ring-constrained amino acid surrogates of formula I and linear or cyclic compounds which include a plurality of amino acid residues and one or more ring-constrained amino acid surrogates of formula I.