Cα-methyl,Cα-allylglycine (Mag) homooligomers

A complete series of Nα-protected, monodispersed homooligopeptide esters to the pentamer level from L-Cα-methyl,Cα-allylglycine (L-Mag) have been synthesized step-by-step in solution and fully characterized. The solution preferred conformation of these homooligomers has been assessed by FT-IR absorption and 1H NMR techniques. Moreover, the molecular structures of the homedimer and trimer have been determined in the crystal state by X-ray diffraction, and the conformational energy map of the homotrimer has been computed. The results obtained point to the conclusion that right-handed, single, or multiple β-bends are preferentially adopted by the conformationally restricted L-Mag homooligomers. In particular, 310-helices are formed by the longest homooligomer (pleionomer). The implications for the use of the Mag residue in designing conformationally constrained peptide substrates for reactions involving the side-chain C=C functionality are briefly discussed