Synthesis of selenoxo peptides and oligoselenoxo peptides employing LiAlHSeH.

Synthesis of selenoxo peptides by the treatment of N(α)-protected peptide esters with a combination of PCl(5) and LiAlHSeH is delineated. The method is simple, high-yielding, and free from racemization. Thus obtained selenoxo peptides are used as units for N-terminal chain extension through N(α)-deprotection/coupling to yield peptide-selenoxo peptide hybrids. Multiple selenation is demonstrated by conversion of two peptide bonds of tripeptides into selenoxo peptide bonds. Amino acid derived arylamides are also converted into aryl selenoamides. C(6)H(5)-CSeNH-Val-OMe 8f is obtained as single crystal, and its structure was determined through X-ray diffraction study.