Synthesis of selenoxo peptides by the treatment of N α-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 N α-deprotection/coupling to yield peptide–selenoxo peptide hybrids. Multiple selenation is demonstrated by conversion of two peptide bonds of ...