The stereospecific synthesis of ‘orthogonally’ protected lanthionines

Lanthionine is an attractive monomer for the design and synthesis of novel conformationally constrained peptidomimetics, since unlike cystine, the monosulfur bridge of lanthionine is chemically far more robust and also displays a greater degree of conformational rigidity. The synthesis of lanthionine residues for use in peptide synthesis is non-trivial due to the protectional requirements necessary for this tetra-functional amino acid. In this paper an efficient stereo-specific route to orthogonally protected lanthionine is described.