Synthesis of Selenoxo Peptides and Oligoselenoxo Peptides Employing LiAlHSeH

Synthesis of selenoxo peptides by the treatment of Nα-protected peptide esters with a combination of PCl5 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 Nα-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. C6H5-CSeNH-Val-OMe 8f is obtained as single crystal, and its structure was determined through X-ray diffraction study.