Solid phase synthesis of peptides containing the CH2NH peptide bond isostere

The CH2NH peptide bond can be directly introduced by the reductive alkylation reaction between a tert-butoxycarbonyl-amino acid aldehyde and an amine on the resin bound peptide employing sodium cyanoborohydride in acidified dimethylformamide solution and this facile method was successfully applied to the synthesis of a psiCH2NH] pseudopeptide somatostatin octapeptide analogue.