An access to aza-Freidinger lactams and E-locked analogs.

Freidinger lactams, possessing a peptide bond configuration locked to Z, are important key elements of conformationally restricted peptidomimetics. In the present work, the C(α)H(i+1) unit has been replaced by N, leading to novel aza-Freidinger lactams. A synthesis to corresponding building blocks and their E-locked analogs is introduced. The versatile buildings blocks reported here are expected to serve as useful elements in peptide synthesis.