The synthesis of a series of conformationally constrained peptidomimetics containing a 9-to-13-atom-membered ring by ring-closing metathesis (RCM) is described. The second-generation Grubbs catalyst proved to be the most effective in producing the desired cyclic β-peptidomimetics with moderate to good yields. Reaction characteristics such as the influence of alkene chain length in the precursors, position of double bond and ring size of products were also discussed.

A peptide biphenyl hybrid compound {systematic name: dimethyl 2,2′-[((2S,2′S)-2,2′-{[(2S,2′S)-1,1′-([1,1′-biphenyl]-2,2′-dicarbonyl)bis(pyrrolidine-1,2-diyl-2-carbonyl)]bis(azanediyl)}bis(3-phenylpropanoyl))bis(azanediyl)](2S,2′S)-dipropionate hemihydrate}, C50H56N6O10·0.5H2O, was prepared by coupling of [1,1′-biphenyl]-2,2′-dicarbonyl dichloride, triethylamine and the tripeptide Pro–Phe–Ala in CH2Cl2 at 273 K under an N2 atmosphere. In the crystal, the asymmetric unit contains the peptide biphenyl hybrid accompanied by one-half of a water molecule. A C atom of one of the proline rings is disordered between two positions in a 0.746 (11):0.254 (11) ratio. An important structural aspect of peptide compounds is their capacity to self-associate mediated by intermolecular and intramolecular hydrogen bonding. This characteristic can be useful in understanding the interactions between peptides and biomacromolecular targets, as well as to explain peptide properties.