β,β‐Dimethylcyclolanthionines, New Constrained Dipeptide Mimetics: Synthesis, Crystal Structures, and Conformational Studies

The labile disulfide bridge between cysteine residues in naturally occurring peptides can be replaced by lanthionine, as demonstrated by the synthesis of conformation-ally constrained dipeptide mimetics (see below) based on β,β-dimethylcyclolanthio-nines. Their structural features indicate that they represent a novel family of peptidomimetics.