Novel Gly building units for backbone cyclization: Synthesis and incorporation into model peptides

We report the preparation of novel building units for backbone cyclization that have the general formula Fmoc-N^α[CH(R)CO ₂Al]Gly-OH. These building units were prepared by the reductive alkylation method using allyl esters of several amino acids as starting material and hence, respectively, contain the side chain of these amino acids. These N-alkylated Gly building units were incorporated in model backbone cyclic peptides. The resulting crude backbone cyclic peptides were obtained in high degree of purity according to HPLC and mass spectrometric analyses.